Engelskaflevering d. 01.09.95
"Green laws boost clean-up industry"
I
Have companies around the globe really become "house-proud", or is planet earth just in for a spring cleaning? It is hard to say - but one thing is for sure; the environmental sector is en-joying a boom. The market for pollution control technology is on a steep exponential growth curve, which seems to be interminable. Especially the European companies put down their names for an immense part of the expansion. But what is the precise nature of this sudden environmental con-cern? After all the deteriorating state of the environment is hardly a novel phenomenon, to say the least.
Just how vigorous this potential goldmine is going to be for the clean-up industry ac-tually depends on law and order, so to speak. That is to say that one of the main reasons for the turn up is new legislation. Recent EU-directives as to pollution may cause heavy demands on the purse of one company and consequently pour that money down the pockets of the clean technology indu-stry. Moreover the deadlines for plants to meet EU-directives are getting close, and everything se-ems to show that the laws will be enforced. Yet far from all companies have to meet with the raised finger of the law to start investing in their environmental responsibilities. Investments on a volunta-ry basis are often due to the fact that it makes good ecnomic sense or because it gives the corporate image a face-lifting.
Seen from a geoprahical point of view Germany and primarily eastern Europe form tremendously good breeding ground for the sale of clean-up equipment. As a result of opencast mi-ning of lignite coal in Poland, for example, a huge clean-up is left, which will amount to billions of dollars. However accidents also occur at sea, where a spate of oil tanker disasters are likely to fill out the order book at oil cleaning industries.
Nevertheless a stroke of bad luck is far from necessary in order to make firms under-stand their green obligations. The power of the consumers has been on the increase over the last few years, and the public environmental image means more to a firm than ever before. The average con-sumer going down to the grocer's for a few necessaries is starting to attach importance to something else than just the product itself. How is the detergent wrapped - is the paper bleached? Is this bottle reusable? Are these outdoor tomatoes? - and so on. Personally I don't think that you notice it, as you're walking alongside the shelves in the local supermarket - but you do pay more attention to ecological messages on the products than you did just 5-10 years ago. After all this is a topic very much in the public mind, so I guess it's quite natural to get involved one way or the other. I know from my own experiences that we have started to put down se-veral ecological products on the shopping list at home, when going to the grocer's. Products like: carrots, rye bread, milk, and cheese appear regularly on our shopping list and always in ecological form. But just recently another common purchase was substituted; red wine, French red wine to be exact, had to give way to a Spanish bottle instead. The day by day "revolution" on the dinner table was my mother's contribution to the prevention of the French nuclear tests. French products in gene-ral was banned on our shopping list - and still are. How far her exertions have got appreciable effect with monsieur Chirac is dubious - but many a little makes a mickle, as they say!
On a more global scale this environmental consciousness of the consumers was to be witnessed just a couple of months ago. The sinking of the drilling rig "Brent Spar" at open sea cau-sed an outcry all over Europe, and customers "rippled their muscles". Shell, the mastermind behind the sinking, was boycott by a vast number of both bulk buying companies and ordinary consumers which resulted in a more environmentally friendly solution at last. To my mind this way of carrying one's point is absolutely excellent. Henceforward I feel that the consumers should utilize "the power of their shopping list" far more frequently. As to "Brent Spar", we kept that one afloat and got it sent to the breakers pre-venting the environment from further molestation. Let's only hope that this will go for the French nuclear weapons as well - before it's too late! "Consumers, unite!"
III
COWIconsult
Parallelvej 15
2800 Lyngby
Denmark
The European
Att.: Michael Bond
Orbit House
5 New Fetter lane
London EC4A 1AP
U.K. 12 June 1994
Dear Sir
Thanks for your letter of 6 June. I regret that I unfortunately can not answer your question, since we are a consulting firm which is not directly involved in any environmental acitvities.
The environmental sector has truely enjoyed a boom during the past few years. Industry is begin-ning to take its green responsibility seriously, consequently we help the companies in finding out whether they can make profits from a green image or not. For instance we do calculations for com-panies so that they can see the financial consequences of any environmental investments.
That is why we can not be of any assistance to you regarding information on special projects. However we do enclose our latest annual report, where you will find the names of some Danish firms, which have been involved in either the cleaning of polluted soil in eastern Europe or the sale of equipment for monitoring oil spill from ship tanks in the North Sea. Perhaps you can obtain fur-ther details at the mentioned companies.
Moreover we refer to our office in London, 35 Bassinghall Street, London EC2V 5DB.
We wish you the best of luck on your articles.
Yours sincerely
COWIconsult
Marlene Eriksen
Marlene Eriksen
Information Manager
Encl
4
Sunday, October 14, 2012
Global Warming
Mission Plan
a. Analysis of the Problem
1. History of the Problem
Some scientist's have been concerned since 1896 about what might happen if there
were 5.5 billion tons carbon dioxide in our atmosphere. In 1961 a British scientist did an
experiment showing that the carbon in the air was absorbing some of the sun's radiation.
Afterward a Swedish scientist, Suante Arrhenius, found out if the radiation of the sun was
trapped in the carbon dioxide the temperature of the earth would increase by 1-2 degrees.
In 1988 James Hanson, a respected scientist, told the U.S. Congress "the greenhouse
effect is occurring now and it's changing global climate."(1989 Koral). After the 1900's
people started making factories and started using fossil fuels like coal, oil, and aluminum.
It was the industrial revolution and overpopulation of humans that was the cause of the
environmental problems that we have today.
2. Human Activity Causing the Problem
The reason our Earth is getting hotter is that human activities are emitting too
much carbon dioxide into the atmosphere. The radiation from the sun gets trapped in the
bag of carbon dioxide that surrounds our earth.
One main reason for the problem of global warming is the burning of fossil fuels.
Fossil fuels are coal, oil and natural gases. We use these fuels to run factories, power
plants, cars, trucks, buses, air conditioning and etc. The people of the earth are putting
5.5 billion tons of carbon, in the form of carbon dioxide in the air every year! Seventy
five percent of this is fossil fuels.
3. Impact Causing Global Change
For many years, scientists have been predicting that our disregard for Mother
Nature would make the climatic temperature of this Earth to increase greatly. There have
been arguments that the whole idea of Global Warming is a hoax, that the temperature
cycle is just experiencing an upward trend and will eventually come back down. Now,
however, we are starting to see the evidence of our behavior.
Remember the great heat wave in Chicago? That could have been a consequence
of global warming. Nearly a hundred people died, and the city's economy came to a
standstill. A much more tragic but less known heat wave smashed into India, causing
upward of 600 deaths.
Global Warming doesn't only increase temperatures in hot areas. It also decreases
temperatures in cold areas. An example of this has been the cold spell that struck the
midwest. In Montana, temperatures plummeted to 30 degrees below and stayed there.
The coldest weather ever recorded plagued our country's heart for over three weeks, and
still hasn't returned to normal. A related incident has been the blizzards of the east coast.
Some places in New York State got over twenty feet of snow.
On a Native Island, where native tribes live, if the sea level rises three fourths of a
meter then half of the island will sink. This will happen in many different islands around
the world and if the water keeps on rising as it is, then farming land near the seashores
will be flooded and the crops will be destroyed.
Like California and other states, we are adding CO2 and changing the earth's
weather. Some places are getting too little water which causes a drought and other places
get too much water which causes a flood.
In California, there was an almost permanent drought during the eighties. This
was gone in the nick of time by the great rainstorms of 1995. We also experienced a
frightening cold spell in 1992.
The Road Ahead
With all these obvious scourges plaguing us now, it seems that things cannot get
any worse. However, the current droughts, floods, and storms are just the tip of the
iceberg. If the greenhouse effect continues unabated, then the inhabitants of Planet Earth
have some surprises in store.
Scientists estimate that the global temperature will rise between 5 and 9 degrees
by the middle of the 21st century, accompanied by a sea-level rise of one to four feet. Five
degrees may not seem like a drastic change, but in the last ice age at the beginning of the
Quaternary period, the average temperature was only five degrees colder than it is now.
Thus, our actions our warming the earth enough to break out of an ice age.
Once the temperature reaches a certain threshold, the polar ice caps will began to
melt. While those living in the Arctic may find that a welcome surprise, the implications
for the rest of the world are serious. Even a partial melting of the polar ice caps will cause
sea levels to rise so much as to completely wipe out most coastal cities. This includes
such cultural centers as San Francisco and New York. Those cities that survive will be
battered down by hurricanes much more severe than anything seen in history. Of course,
inland cities are not immune either. Rather than floods, they will face drought. So while
half the world is swimming to work, the other half will be crawling on their knees with a
scorching sun beating against their backs.
When drinkable water is a scarcity, it will become a commodity that represents
political power. The countries with water will be the countries with power. This means
there will be a political upheaval of global proportions. Life as our children know it will be
completely different, and not necessarily for the better. With most of America's lakes
dried up and its major trading ports under several feet of salt water, perhaps we won't be
the economical leader.
If we don't start trying to stop global warming from happening now, there will be
many more consequences. Another consequence will be that there will be high raises in
temperature, affecting human life by causing skin cancer, damaging the human immune,
and causing cataracts. Raises in temperature will also affect agricultural and aquatic life.
Also, many species will die off. And in the forests or maybe animals, there could be
medicines to cure some kind of disease. The way these cancers and diseases come to be
is because the sun deadly rays like UV rays, which mutate human cells.
b. Experimental Design
1. Restate Problem
Natural occurrences are not the only caused and influences of our atmosphere
changing. Human activities also cause the atmosphere to change. Fossil fuels burning is
producing a worldwide increase in the atmosphere concentration of carbon dioxide. If
atmospheric carbon dioxide continues to increase at the present rate, studies estimate that
the average surface temperature will rise 2 degrees Celsius by the middle of the next
century. This will be a climate change greater than any other ever experienced in history,
that we know of. The four main greenhouse gases are Carbon Dioxide (CO2),
Chlorofluorocarbons (CFCs), Methane (CH4), and Nitrous Oxide (N2O). With the
exception of CFCs, all these gases are found in nature. It is the recent explosion of the
human population that has caused an exponential increase in their atmospheric presence.
Although nature has provisions for removing carbon dioxide, it does not take into
account the human factor. The long, complicated carbon cycle can only keep up with
increasing human activity if the tree population increases proportionately. Due to modern
medicine and increased awareness of nutrition and health, the human race has managed to
extend its lifespan considerably, thereby releasing more CO2 into the atmosphere. This,
combined with an alarming rate of rainforest depletion and air pollution, leads to an
unmanageable amount of CO2 in the atmosphere. Since its sources are both natural and
human, carbon dioxide is the largest contributor to the greenhouse effect, at 50%.
As far as CFCs, our only excuse is that "it seemed a good idea at the time." When
they were first invented, they seemed to be the miracle chemical of the century. Because
of their low boiling point, CFCs could act as coolers in refrigerators, freezers, and air
conditioners. Also, they were used to make Styrofoam and as aerosol propellants. As it
turns out, they are as skilled at destruction as they are at refrigerating. Scientists
discovered in the 1970's that CFCs destroy ozone, starting an international ban on their
usage. Later, it was determined that CFCs contribute to global warming as well, making
them a dangerous double whammy. CFCs are no longer used in aerosol and Styrofoam,
however most refrigerators still contain freon, a CFC. Fortunately, the freon can be
recycled. Contributing to 25% of global warming, CFCs are still a major problem, but at
least the U.S. and the other powers have recognized it as such. Methane, also known as a
natural gas, contributes 15% to the greenhouse effect. It is caused by cows and rice
paddies. The major American demand for so much beef urges foreign farmers to clear
forests for pastures. This also causes an increase in carbon dioxide, as well as a cow
population so high that the methane-rich burps of the complex digestive system are a
major contributing factor to the greenhouse effect. Add to that the methane released from
natural sources, and you have a very large problem. The ten percent that is left comes
from nitrous oxide, a common pollutant. It, along with carbon dioxide, forms the major
part of car exhaust. Half a billion cars drive the streets of the world today, a number
expected to double by 2030. N2O is also released by the burning of fossil fuels. Finally,
it finds its way into the atmosphere from nitrogen fertilizers, which are used heavily by
today's modern farmers.
Overall there are many pollutants in our atmosphere, influenced by humans, and
by natural effects. In our opinion if any member of this country wants to live in a good
environment then they have to take charge and to make a difference even if you have to
become a vegetarian so there will not be CO2 from the animals.
2. Hypothesis
If we continue to pollute the air with methane gases and don't do anything about
it, then the average global temperature will rise and there will be many consequences.
Warming expands ocean water and may melt some glaciers. The sea level could rise one
foot in the next 35 years and two in the next 100. Hurricanes, tornadoes and other
extreme storms may become more frequent. Centers of large continents, such as the U.S.
Great Plains, may be drier even if the overall world rainfall increases somewhat. Heat
waves may be more common. Movement of just 1 percent of a future population of 6
billion people due to higher sea level, drought, or other climate change would produce 60
million migrants, many times the number of all refugees today. Impact mixed. Carbon
dioxide stimulates plant growth. However, heat increases demand for water. Growing
zones will shift if weather patterns change. Warming that expands the tropics will also
expand the range of tropical diseases such as malaria and other insect borne maladies.
Possible mass extinction may occur as conditions change faster than species can move or
adapt. Urban and agriculture development leaves few wilderness corridors for migration.
3. EOS Satellite
The Earth Observing System (EOS) Data and Information System (EOSDIS)
is NASA's Mission to Planet Earth's (MTPE) project to provide access to Earth Science
data. EOSDIS manages data from NASA's past and current Earth science research
satellites and field measurement programs, providing data archiving, distribution, and
information management services. During the EOS era--beginning with the launch of the
TRMM satellite in 1997 EOSDIS will command and control satellites and instruments,
and will generate useful products from orbital observations. EOSDIS will also generate
data sets made by assimilation of satellite and in situ observations into global climate
models.
The instrument that we chose that monitors the impact of human activity is
HIRDLS. HIRDLS is an infrared limb-scanning radiometer designed to sound the upper
troposphere, stratosphere, and mesosphere to determine temperature; the concentrations
of O3, H2O, CH4, N2O, NO2, HNO3, N2O5, CFC11, CFC12, and aerosols; and the
locations of polar stratospheric clouds and cloud tops. The goals are to provide sounding
observations with horizontal and vertical resolution superior to that previously obtained;
to observe the lower stratosphere with improved sensitivity and accuracy; and to improve
understanding of atmospheric processes through data analysis, diagnostics, and use of
two- and three-dimensional models.
HIRDLS performs limb scans in the vertical at multiple azimuth angles, measuring
infrared emissions in 21 channels ranging from 6.12 to 17.76 um. Four channels measure
the emission by CO2. Taking advantage of the known mixing ratio of CO2, the
transmittance is calculated, and the equation of radiative transfer is inverted to determine
the vertical distribution of the Planck black body function, from which the temperature is
derived as a function of pressure. Once the temperature profile has been established, it is
used to determine the Planck function profile for the trace gas channels. The measured
radiance and the Planck function profile are then used to determine the transmittance of
each trace species and its mixing ratio distribution.
Winds and threatening tornados are determined from spacial variations of the
height of geopotential surfaces. These are determined at upper levels by integrating the
temperature profiles vertically from a known reference base. HIRDLS will improve
knowledge of data-sparse regions by measuring the height variations of the reference
surface provided by customary sources with the aid of a gyro package. This level, which
is near the base of the stratosphere can also be blended downward using nadir
temperature soundings to improve tropospheric analyses.
Bibliography
"Climate Change Brings Trouble". The Earth Care Annual 1993. Emmaus:
Rodale Press, 1993
"EOS" http://eos.nasa.gov/ Logon November 3, 1996
"Global Warming" http://users.aimnet.com/~hyatt/gw/gw.html Logon October 25,
1996
"Global Warming". Microsoft Encarta 95, Microsoft, 1994.
"HIRDL" http://eos.acd.ucar.edu/hirdls/home.html Logon November 1, 1996
Newton, David. Global Warming A Reference Handbook. Santa Barbara:
ABC-CLIO, 1993
Silver, Cheryl. One Earth, One Future, Our Changing Global Environment.
Washington D.C., National Academy Press, 1990
Woodwell, George. The Rising Tide Global Warming and World Sea Levels.
Washington D.C., Island Press, 1991
a. Analysis of the Problem
1. History of the Problem
Some scientist's have been concerned since 1896 about what might happen if there
were 5.5 billion tons carbon dioxide in our atmosphere. In 1961 a British scientist did an
experiment showing that the carbon in the air was absorbing some of the sun's radiation.
Afterward a Swedish scientist, Suante Arrhenius, found out if the radiation of the sun was
trapped in the carbon dioxide the temperature of the earth would increase by 1-2 degrees.
In 1988 James Hanson, a respected scientist, told the U.S. Congress "the greenhouse
effect is occurring now and it's changing global climate."(1989 Koral). After the 1900's
people started making factories and started using fossil fuels like coal, oil, and aluminum.
It was the industrial revolution and overpopulation of humans that was the cause of the
environmental problems that we have today.
2. Human Activity Causing the Problem
The reason our Earth is getting hotter is that human activities are emitting too
much carbon dioxide into the atmosphere. The radiation from the sun gets trapped in the
bag of carbon dioxide that surrounds our earth.
One main reason for the problem of global warming is the burning of fossil fuels.
Fossil fuels are coal, oil and natural gases. We use these fuels to run factories, power
plants, cars, trucks, buses, air conditioning and etc. The people of the earth are putting
5.5 billion tons of carbon, in the form of carbon dioxide in the air every year! Seventy
five percent of this is fossil fuels.
3. Impact Causing Global Change
For many years, scientists have been predicting that our disregard for Mother
Nature would make the climatic temperature of this Earth to increase greatly. There have
been arguments that the whole idea of Global Warming is a hoax, that the temperature
cycle is just experiencing an upward trend and will eventually come back down. Now,
however, we are starting to see the evidence of our behavior.
Remember the great heat wave in Chicago? That could have been a consequence
of global warming. Nearly a hundred people died, and the city's economy came to a
standstill. A much more tragic but less known heat wave smashed into India, causing
upward of 600 deaths.
Global Warming doesn't only increase temperatures in hot areas. It also decreases
temperatures in cold areas. An example of this has been the cold spell that struck the
midwest. In Montana, temperatures plummeted to 30 degrees below and stayed there.
The coldest weather ever recorded plagued our country's heart for over three weeks, and
still hasn't returned to normal. A related incident has been the blizzards of the east coast.
Some places in New York State got over twenty feet of snow.
On a Native Island, where native tribes live, if the sea level rises three fourths of a
meter then half of the island will sink. This will happen in many different islands around
the world and if the water keeps on rising as it is, then farming land near the seashores
will be flooded and the crops will be destroyed.
Like California and other states, we are adding CO2 and changing the earth's
weather. Some places are getting too little water which causes a drought and other places
get too much water which causes a flood.
In California, there was an almost permanent drought during the eighties. This
was gone in the nick of time by the great rainstorms of 1995. We also experienced a
frightening cold spell in 1992.
The Road Ahead
With all these obvious scourges plaguing us now, it seems that things cannot get
any worse. However, the current droughts, floods, and storms are just the tip of the
iceberg. If the greenhouse effect continues unabated, then the inhabitants of Planet Earth
have some surprises in store.
Scientists estimate that the global temperature will rise between 5 and 9 degrees
by the middle of the 21st century, accompanied by a sea-level rise of one to four feet. Five
degrees may not seem like a drastic change, but in the last ice age at the beginning of the
Quaternary period, the average temperature was only five degrees colder than it is now.
Thus, our actions our warming the earth enough to break out of an ice age.
Once the temperature reaches a certain threshold, the polar ice caps will began to
melt. While those living in the Arctic may find that a welcome surprise, the implications
for the rest of the world are serious. Even a partial melting of the polar ice caps will cause
sea levels to rise so much as to completely wipe out most coastal cities. This includes
such cultural centers as San Francisco and New York. Those cities that survive will be
battered down by hurricanes much more severe than anything seen in history. Of course,
inland cities are not immune either. Rather than floods, they will face drought. So while
half the world is swimming to work, the other half will be crawling on their knees with a
scorching sun beating against their backs.
When drinkable water is a scarcity, it will become a commodity that represents
political power. The countries with water will be the countries with power. This means
there will be a political upheaval of global proportions. Life as our children know it will be
completely different, and not necessarily for the better. With most of America's lakes
dried up and its major trading ports under several feet of salt water, perhaps we won't be
the economical leader.
If we don't start trying to stop global warming from happening now, there will be
many more consequences. Another consequence will be that there will be high raises in
temperature, affecting human life by causing skin cancer, damaging the human immune,
and causing cataracts. Raises in temperature will also affect agricultural and aquatic life.
Also, many species will die off. And in the forests or maybe animals, there could be
medicines to cure some kind of disease. The way these cancers and diseases come to be
is because the sun deadly rays like UV rays, which mutate human cells.
b. Experimental Design
1. Restate Problem
Natural occurrences are not the only caused and influences of our atmosphere
changing. Human activities also cause the atmosphere to change. Fossil fuels burning is
producing a worldwide increase in the atmosphere concentration of carbon dioxide. If
atmospheric carbon dioxide continues to increase at the present rate, studies estimate that
the average surface temperature will rise 2 degrees Celsius by the middle of the next
century. This will be a climate change greater than any other ever experienced in history,
that we know of. The four main greenhouse gases are Carbon Dioxide (CO2),
Chlorofluorocarbons (CFCs), Methane (CH4), and Nitrous Oxide (N2O). With the
exception of CFCs, all these gases are found in nature. It is the recent explosion of the
human population that has caused an exponential increase in their atmospheric presence.
Although nature has provisions for removing carbon dioxide, it does not take into
account the human factor. The long, complicated carbon cycle can only keep up with
increasing human activity if the tree population increases proportionately. Due to modern
medicine and increased awareness of nutrition and health, the human race has managed to
extend its lifespan considerably, thereby releasing more CO2 into the atmosphere. This,
combined with an alarming rate of rainforest depletion and air pollution, leads to an
unmanageable amount of CO2 in the atmosphere. Since its sources are both natural and
human, carbon dioxide is the largest contributor to the greenhouse effect, at 50%.
As far as CFCs, our only excuse is that "it seemed a good idea at the time." When
they were first invented, they seemed to be the miracle chemical of the century. Because
of their low boiling point, CFCs could act as coolers in refrigerators, freezers, and air
conditioners. Also, they were used to make Styrofoam and as aerosol propellants. As it
turns out, they are as skilled at destruction as they are at refrigerating. Scientists
discovered in the 1970's that CFCs destroy ozone, starting an international ban on their
usage. Later, it was determined that CFCs contribute to global warming as well, making
them a dangerous double whammy. CFCs are no longer used in aerosol and Styrofoam,
however most refrigerators still contain freon, a CFC. Fortunately, the freon can be
recycled. Contributing to 25% of global warming, CFCs are still a major problem, but at
least the U.S. and the other powers have recognized it as such. Methane, also known as a
natural gas, contributes 15% to the greenhouse effect. It is caused by cows and rice
paddies. The major American demand for so much beef urges foreign farmers to clear
forests for pastures. This also causes an increase in carbon dioxide, as well as a cow
population so high that the methane-rich burps of the complex digestive system are a
major contributing factor to the greenhouse effect. Add to that the methane released from
natural sources, and you have a very large problem. The ten percent that is left comes
from nitrous oxide, a common pollutant. It, along with carbon dioxide, forms the major
part of car exhaust. Half a billion cars drive the streets of the world today, a number
expected to double by 2030. N2O is also released by the burning of fossil fuels. Finally,
it finds its way into the atmosphere from nitrogen fertilizers, which are used heavily by
today's modern farmers.
Overall there are many pollutants in our atmosphere, influenced by humans, and
by natural effects. In our opinion if any member of this country wants to live in a good
environment then they have to take charge and to make a difference even if you have to
become a vegetarian so there will not be CO2 from the animals.
2. Hypothesis
If we continue to pollute the air with methane gases and don't do anything about
it, then the average global temperature will rise and there will be many consequences.
Warming expands ocean water and may melt some glaciers. The sea level could rise one
foot in the next 35 years and two in the next 100. Hurricanes, tornadoes and other
extreme storms may become more frequent. Centers of large continents, such as the U.S.
Great Plains, may be drier even if the overall world rainfall increases somewhat. Heat
waves may be more common. Movement of just 1 percent of a future population of 6
billion people due to higher sea level, drought, or other climate change would produce 60
million migrants, many times the number of all refugees today. Impact mixed. Carbon
dioxide stimulates plant growth. However, heat increases demand for water. Growing
zones will shift if weather patterns change. Warming that expands the tropics will also
expand the range of tropical diseases such as malaria and other insect borne maladies.
Possible mass extinction may occur as conditions change faster than species can move or
adapt. Urban and agriculture development leaves few wilderness corridors for migration.
3. EOS Satellite
The Earth Observing System (EOS) Data and Information System (EOSDIS)
is NASA's Mission to Planet Earth's (MTPE) project to provide access to Earth Science
data. EOSDIS manages data from NASA's past and current Earth science research
satellites and field measurement programs, providing data archiving, distribution, and
information management services. During the EOS era--beginning with the launch of the
TRMM satellite in 1997 EOSDIS will command and control satellites and instruments,
and will generate useful products from orbital observations. EOSDIS will also generate
data sets made by assimilation of satellite and in situ observations into global climate
models.
The instrument that we chose that monitors the impact of human activity is
HIRDLS. HIRDLS is an infrared limb-scanning radiometer designed to sound the upper
troposphere, stratosphere, and mesosphere to determine temperature; the concentrations
of O3, H2O, CH4, N2O, NO2, HNO3, N2O5, CFC11, CFC12, and aerosols; and the
locations of polar stratospheric clouds and cloud tops. The goals are to provide sounding
observations with horizontal and vertical resolution superior to that previously obtained;
to observe the lower stratosphere with improved sensitivity and accuracy; and to improve
understanding of atmospheric processes through data analysis, diagnostics, and use of
two- and three-dimensional models.
HIRDLS performs limb scans in the vertical at multiple azimuth angles, measuring
infrared emissions in 21 channels ranging from 6.12 to 17.76 um. Four channels measure
the emission by CO2. Taking advantage of the known mixing ratio of CO2, the
transmittance is calculated, and the equation of radiative transfer is inverted to determine
the vertical distribution of the Planck black body function, from which the temperature is
derived as a function of pressure. Once the temperature profile has been established, it is
used to determine the Planck function profile for the trace gas channels. The measured
radiance and the Planck function profile are then used to determine the transmittance of
each trace species and its mixing ratio distribution.
Winds and threatening tornados are determined from spacial variations of the
height of geopotential surfaces. These are determined at upper levels by integrating the
temperature profiles vertically from a known reference base. HIRDLS will improve
knowledge of data-sparse regions by measuring the height variations of the reference
surface provided by customary sources with the aid of a gyro package. This level, which
is near the base of the stratosphere can also be blended downward using nadir
temperature soundings to improve tropospheric analyses.
Bibliography
"Climate Change Brings Trouble". The Earth Care Annual 1993. Emmaus:
Rodale Press, 1993
"EOS" http://eos.nasa.gov/ Logon November 3, 1996
"Global Warming" http://users.aimnet.com/~hyatt/gw/gw.html Logon October 25,
1996
"Global Warming". Microsoft Encarta 95, Microsoft, 1994.
"HIRDL" http://eos.acd.ucar.edu/hirdls/home.html Logon November 1, 1996
Newton, David. Global Warming A Reference Handbook. Santa Barbara:
ABC-CLIO, 1993
Silver, Cheryl. One Earth, One Future, Our Changing Global Environment.
Washington D.C., National Academy Press, 1990
Woodwell, George. The Rising Tide Global Warming and World Sea Levels.
Washington D.C., Island Press, 1991
Global Warming and Human Population
The relationship between humans and the state of the ecosystem is not only dependent upon how many people there are, but also upon what they do. When there were few people, the dominant factors controlling ecosystem state were the natural ones that have operated for millions of years. The human population has now grown so large that there are concerns that they have become a significant element in ecosystem dynamics. One of these concerns is the relationship between human activities and climate, particularly the recent observations and the predictions of global warming, beginning with the alarm sounded by W. Broecker (1975).
The relationships among humans, their activities and global temperature can be assessed by making the appropriate measurements and analyzing the data in a way that shows the connections and their magnitudes. Human population can be closely estimated and the consequences of their activities can be measured. For example, the volume of carbon dioxide, methane and nitrous oxide emissions is an indicator of human's energy and resource consumption. An examination of population size, atmospheric concentrations of these gases and global temperature relative to time and with respect to each other is presented here to demonstrate the relations among these factors.
POPULATION GROWTH
Many of us have seen linear graphs of human population showing the enormous growth in the last two centuries. However, significant changes in population dynamics are lost in the exponential growth and long time scales. If the data are replotted on a log-population by log-time scale, significant population dynamics emerge. First, it is apparent that population growth has occurred in three surges and second, that the time between surges has dramatically shortened (Deevey, 1960).
<Picture>Figure 1. Population (Log-population verses log-time since 1 million years ago). Time values on x-axis, ignoring minus sign, are powers of 10 years before and after 1975 (at 0). Vertical dashed-line at 1995. Filled circles for known values are to left of 1995 and open circles on and to right of 1995 are for projected values. (Data updated from Deevey, 1960).
----------
Deevey's 1960 graph has been brought up to date in Figure 1 to reflect what has been learned since then. The data have been plotted relative to 1975 with negative values before 1975 and positive values thereafter. The reason for this will become clear below. The values of the time scale, ignoring the minus signs, represent powers of 10 years.
It has been argued that a population crash occurred about 65,000 years ago (-4.8, Fig. 1), presumably due to the prolonged ice-ages during the preceding 120,000 years (Gibbons, 1993). Humans came close to perishing and Neanderthal became extinct. However, by 50,000 years ago (-4.6, Fig. 1), humans had generated population mini-explosions all around the planet. Deevey's data for population size since 500 years ago have been replaced with more recent estimates taken from The World Almanac, (1992 - 1995) including population projections out to 2025. A vertical dashed-line has been placed at 1995. Filled symbols for the known values are to the left of it and open symbols on and to the right of it are for values projected into the short-term future.
The first surge coincides with the beginning of the cultural revolution about 600,000 years ago, interrupted by the population crash 65,000 years ago. Population size rebounded 50,000 years ago and then growth slowed considerably. The second surge began with the agricultural revolution about 10,000 years ago and was followed by slow growth. Deevey argued that moving down the food chain was the underlying cause of this large and rapid spurt. The timing of the present surge matches the rise of the industrial-medical revolution 200 years ago.
A relation between innovation and population growth is embedded in the log-log plot. There was rapid growth at the start of each surge. Then, growth rate slowed as people adapted to the precipitating innovations. Each surge increased the population more than 10-fold. It appears that we are nearing the end of the present surge as recent growth rates have declined. After the initial spurt, subsequent innovations did not perpetuate growth rates. The only significant innovations were those that produced the next surge. However, accumulated innovations during the surges may have played a role in the eventual decline in population growth rates. Starting with high birth and death rates, death rate declines and longevity increases, but birth rates stay high. Some time later, birth rates decline so that eventually, net births minus deaths produces slow growth. The result is a spurt in population size. When referring to the industrial revolution, this phenomenon has been called the "demographic transition". It appears that this dynamic may have occurred twice before.
The decreases in time between surges suggests that, if past behavior is the best predictor of future behavior, we are due for another surge. It may have already begun, as indicated by the upturn in the projections at the right end of the curve in Figure 1. What might the basis for another surge be? One can think of several possibilities, including the "green revolution" and the "global economy". A dominant element in past surges has been innovations in energy use (e.g., fire, descending the food-chain, beasts of burden, fossil fuels, high-energy agriculture). Thus, the development of an abundant and cheap energy source would have a profound effect. Another 10-fold (or more) surge would produce a population of 60 to 125 billion.
GLOBAL TEMPERATURE AND GREENHOUSE GASES
<Picture>Figure 2. Greenhouse Gases and Mean Global Temperature (Greenhouse gas concentrations and mean global temperature verses time). Time scale same as in Fig. 1. Gas-concentration data have been normalized to the 0 to 1 scale on left: CO2 (squares) - 190 to 430 ppm; CH4 (triangles) - 600 to 2400 ppb; N2O (diamonds) - 280 to 340 ppb. Mean global temperature (circles) plotted relative to oC on right. Vertical dashed-line at 1995, horizontal dotted line at maximum CO2 concentration and global temperature over human history before 1990. Filled and open symbols same as in Fig. 1. Projections in short-term future are based upon continuation at current growth rates. (Data measured from graphs in Gribbin, 1990 and Khalil and Rasmussen, 1992).
----------
Mean-global-temperature (MGT) is related to the concentration of greenhouse gases (carbon dioxide, methane, nitrous oxide, water vapor and other trace gases) in the atmosphere. The most prevalent greenhouse gas is carbon dioxide (CO2). It has been shown that there is a strong relation between the atmospheric concentration of CO2 and MGT over the last 160,000 years (Gribbin, 1990). It has been suspected that the burning of fossil fuels and the clearing of land has reached such proportions that these activities have precipitated a significant increase in atmospheric CO2 concentration. The concentrations of greenhouse gases in the atmosphere have been directly measured since about 1960 and have been determined over the more distant past from air-bubbles trapped in old Antarctic, Greenland and Siberian ice and from deep-sea sediments. Mean-global-temperature has also been measured directly over the last few decades. Estimates of global temperature in the distant past have been deduced from a variety of sources. From these data, the relation among atmospheric greenhouse-gas concentrations, MGT and time is illustrated in Figure 2.
The time scale in Figure 2 is the same as that in Figure 1. Because CO2, methane (CH4) and nitrous oxide (N2O) concentrations have different scales, the data have been normalized on a 0 to 1 scale on the left. For CO2 (squares; Gribbin, 1990), 0 is equivalent to 190 parts per million (ppm) and 1 is equivalent to 430 ppm. For CH4 (triangles; R. Cicerone in Gribbin, 1990), the range is 600 to 2400 parts per billion (ppb). For N2O (diamonds; Khalil and Rasmussen, 1992), the scale is 280 to 340 ppb. Mean global temperature (circles; Gribbin, 1990) has been graphed relative to the degrees-centigrade scale on the right. The vertical dashed-line is the same as that in Figure 1. The horizontal dotted-line is the highest CO2 concentration and temperature in human history before 1990. Greenhouse-gas concentrations and MGT in the short-term future are based upon continuation at the current growth rates. This will be justified in another context below.
<Picture>Figure 3. Population and Global Warming (CO2 concentration and mean global temperature verses log-population) CO2 concentration (circles) and mean global temperature (squares) plotted relative to their absolute scales, ppm on the left and oC on the right, respectively. Vertical dashed line at 1995. (Data from Figs. 1 and 2)
----------
It is clear that the concentrations of all three gases have increased exponentially since 1950 (-1.4, Fig. 2) and that MGT has done so since 1975. Carbon dioxide concentration began to rise in conjunction with the use of fossil fuels after 1850. Although methane comes from a variety of sources, including plant decay, termites and bovine flatulence, CH4 concentration rises at the same time as CO2. This is probably due to its association with fossil-fuel production. Nitrous oxide concentration does not begin to rise until 1950. At this time, the use of human-made fertilizers and internal-combustion-engine exhaust increased dramatically. Ten thousand years ago (-4, Fig. 2), MGT increased substantially just as the agricultural revolution got started. Over the previous 200,000 years, the ecosystem was dominated by ice-ages. Projected MGT in 2025 (1.7, Fig. 2) is about 17oC, 1.5oC higher than in human history prior to 1990.
POPULATION AND GLOBAL TEMPERATURE
We have seen in Figures 1 and 2 that recent population, atmospheric greenhouse-gas concentrations and MGT have grown exponentially over about the same time-course. The relation of CO2 and MGT relative to population size can be observed by graphing these variables as above. Figure 3 shows this graph, where the log of population replaces log-time and CO2 concentration (circles) and MGT (squares) are plotted relative to their absolute scales, ppm on the left and oC on the right, respectively. The vertical dashed-line denotes 1995, as in Figures 1 and 2. When the population reached 4 billion in 1975, the converging relation between population and the other two variables becomes apparent.
The magnitude of the relations in Figures 2 and 3 can be determined by calculating the correlation coefficient between pairs of variables. Table 1 lists these coefficients for the population, greenhouse-gas concentration and MGT variables that we have been examining. The coefficients for the relations during the industrial revolution, 1800 through 1994, are above the diagonal of the table. The coefficients since 2000 years ago through 1994 are below the diagonal. Over the past 2000 years, there is a nearly perfect correlation between the concentration of greenhouse gases and population and between the greenhouse gases themselves. However, the correlations between both population and greenhouse-gas concentrations and MGT (bottom row) are not as strong. After 1800, the latter correlations increase to near perfection (rightmost column). The conclusion from the graphs and table is that there is a strong relationship among population size since 1800, greenhouse-gas concentrations and MGT.
TABLE 1. Correlation coefficients among population size, atmospheric greenhouse-gas concentrations and mean global temperature (1800 through 1994 above the top-left to bottom-right diagonal, n=10; 2000 years ago through 1994 below the diagonal, n=15).
Pop CO2 CH4 N2O Temp
----------
Pop .996 .984 .977 .916
CO2 .990 .994 .974 .942
CH4 .991 .992 .949 .945
N2O .959 .943 .942 .932
Temp .718 .716 .728 .829
GLOBAL WARMING AND CLIMATE
Determining that there is a strong relation between population size and global warming does not tell us what the underlying mechanisms are. However, documentation of the relationship between human activities and the release of greenhouse gases produces a strong inference that population size and global warming are closely related (Gribbin, 1990).
Forecasting the future is risky business. Growth rates for greenhouse-gas concentrations and MGT could decline from those at present due to unanticipated innovations or natural events. For example, volcanoes can spew enough ash into the atmosphere to block sunlight and temporarily reduce MGT slightly. However, short-term continued growth at current rates is probably an underestimate. Although population growth rate has slowed, the population is still growing. The dominating factor is that per-capita energy and resource consumption rates are increasing much faster than the population. This is not only due to anticipated increases in standards of living in underdeveloped countries, but also to future increases in the demand for energy in the developed countries (e.g., air conditioning) as summer temperatures rise. Since most of the energy will come from fossil fuels, at least for the next few decades, we can expect the atmospheric concentrations of greenhouse gases and MGT to rise in the short-term future at a faster rate than they have recently. As MGT rises, water vapor, another greenhouse component, will become a more and more significant factor due to increased evaporation.
Although a 1.5oC increase in MGT above where we were in 1990 (1990 to 2025 in Fig. 2) does not seem like much of a change, it is enough to precipitate major changes in climate. A 1.5oC drop in MGT from where we were in 1990, for example, would put the ecosystem on the verge of an ice-age. Already, there is a suspicion that, since 1975, the persistent El Nino is the first sign of the relation between global warming and climate (Kerr, 1994). As MGT increases further, we can expect more frequent and severe hurricanes and perpetual summertime droughts in many places, particularly in the US Midwest. Paradoxically, more intense winter storms will occur in some places and climatic conditions for agriculture will improve in some areas, such as in Russia (Gribbin, 1990; Bernard, 1993).
There has been considerable debate over the ecosystem's carrying capacity for humans. If we define that carrying capacity as the level that the ecosystem can support without changing state more than it has over the duration of human history, then Figures 2 and 3 indicate that we exceeded that capacity in 1975. This is the point in time where exponential growth began to push MGT along a path which has taken it outside the previous range. This does not necessarily mean that humans could not survive if MGT is about 2oC higher than it has ever been in their history. However, we will have to adapt to a radically different climate pattern and, if MGT goes any higher than that, there could be disastrous problems.
If MGT continues to increase beyond 2025 to 4oC above that in 1990, high-northern-latitude temperatures could be as much as 10oC higher than at the equator. The Arctic ice-cap would begin to melt and the permafrost under the tundra would start thawing out. As a consequence, a thick layer of rotting peat would contribute further to atmospheric CO2 and CH4 concentrations (Gribbin, 1990). With a number of human-made and natural positive-feedback elements in operation simultaneously, a threshold could be crossed (Meyers, 1995; Overpeck, 1996). Are these risks that we should be willing to take for the sake of short-term gains?
REFERENCES
Bernard, H. W. Jr., "Global Warming Unchecked", Indiana Univ. Press, Bloomington, 1993
Broecker, W., Science, 189:460, 1975
Deevey, E. S., Scientific American, 203:195, 1960
Gibbons, A. , Science, 262:27, 1993
Gribbin, J. , "Hothouse Earth", Grove Weidenfeld, New York, 1990
Kerr, R. A., Science, 266:544, 1994
Khalil, M. A. K. and R. A. Rasmussen, J. Geophys. Res., 97:4651, 1992
"The World Almanac", Pharos, New York, 1992 - 1995
Meyers, N. Science 269:358, 1995
Overpeck, J. T. Science, 271:1820, 1996
Post Script
After this document was written (about a 2 years ago), two books came out which provide much more detail relevant to some of these issues:
HOW MANY PEOPLE CAN THE EARTH SUPPORT? by Joel E. Cohen; Norton, 1995.
DIVIDED PLANET: THE ECOLOGY OF RICH AND POOR by Tom Athanasiou; Little Brown, 1996.
Both are superbly done and provide a much more comprehensive and up to date treatment of the population and economic topics included here.
Recent evidence (Mora et al.; SCIENCE 271:1105, 1996) indicates that the possibility of a "greenhouse runaway" on Earth is much more remote than indicated at the end of the previous version of this document. Therefore, the former apocalyptic ending has been changed. Although the data presented points to a catastrophic conclusion, this was (perhaps) an overstatement of the case.
The relationships among humans, their activities and global temperature can be assessed by making the appropriate measurements and analyzing the data in a way that shows the connections and their magnitudes. Human population can be closely estimated and the consequences of their activities can be measured. For example, the volume of carbon dioxide, methane and nitrous oxide emissions is an indicator of human's energy and resource consumption. An examination of population size, atmospheric concentrations of these gases and global temperature relative to time and with respect to each other is presented here to demonstrate the relations among these factors.
POPULATION GROWTH
Many of us have seen linear graphs of human population showing the enormous growth in the last two centuries. However, significant changes in population dynamics are lost in the exponential growth and long time scales. If the data are replotted on a log-population by log-time scale, significant population dynamics emerge. First, it is apparent that population growth has occurred in three surges and second, that the time between surges has dramatically shortened (Deevey, 1960).
<Picture>Figure 1. Population (Log-population verses log-time since 1 million years ago). Time values on x-axis, ignoring minus sign, are powers of 10 years before and after 1975 (at 0). Vertical dashed-line at 1995. Filled circles for known values are to left of 1995 and open circles on and to right of 1995 are for projected values. (Data updated from Deevey, 1960).
----------
Deevey's 1960 graph has been brought up to date in Figure 1 to reflect what has been learned since then. The data have been plotted relative to 1975 with negative values before 1975 and positive values thereafter. The reason for this will become clear below. The values of the time scale, ignoring the minus signs, represent powers of 10 years.
It has been argued that a population crash occurred about 65,000 years ago (-4.8, Fig. 1), presumably due to the prolonged ice-ages during the preceding 120,000 years (Gibbons, 1993). Humans came close to perishing and Neanderthal became extinct. However, by 50,000 years ago (-4.6, Fig. 1), humans had generated population mini-explosions all around the planet. Deevey's data for population size since 500 years ago have been replaced with more recent estimates taken from The World Almanac, (1992 - 1995) including population projections out to 2025. A vertical dashed-line has been placed at 1995. Filled symbols for the known values are to the left of it and open symbols on and to the right of it are for values projected into the short-term future.
The first surge coincides with the beginning of the cultural revolution about 600,000 years ago, interrupted by the population crash 65,000 years ago. Population size rebounded 50,000 years ago and then growth slowed considerably. The second surge began with the agricultural revolution about 10,000 years ago and was followed by slow growth. Deevey argued that moving down the food chain was the underlying cause of this large and rapid spurt. The timing of the present surge matches the rise of the industrial-medical revolution 200 years ago.
A relation between innovation and population growth is embedded in the log-log plot. There was rapid growth at the start of each surge. Then, growth rate slowed as people adapted to the precipitating innovations. Each surge increased the population more than 10-fold. It appears that we are nearing the end of the present surge as recent growth rates have declined. After the initial spurt, subsequent innovations did not perpetuate growth rates. The only significant innovations were those that produced the next surge. However, accumulated innovations during the surges may have played a role in the eventual decline in population growth rates. Starting with high birth and death rates, death rate declines and longevity increases, but birth rates stay high. Some time later, birth rates decline so that eventually, net births minus deaths produces slow growth. The result is a spurt in population size. When referring to the industrial revolution, this phenomenon has been called the "demographic transition". It appears that this dynamic may have occurred twice before.
The decreases in time between surges suggests that, if past behavior is the best predictor of future behavior, we are due for another surge. It may have already begun, as indicated by the upturn in the projections at the right end of the curve in Figure 1. What might the basis for another surge be? One can think of several possibilities, including the "green revolution" and the "global economy". A dominant element in past surges has been innovations in energy use (e.g., fire, descending the food-chain, beasts of burden, fossil fuels, high-energy agriculture). Thus, the development of an abundant and cheap energy source would have a profound effect. Another 10-fold (or more) surge would produce a population of 60 to 125 billion.
GLOBAL TEMPERATURE AND GREENHOUSE GASES
<Picture>Figure 2. Greenhouse Gases and Mean Global Temperature (Greenhouse gas concentrations and mean global temperature verses time). Time scale same as in Fig. 1. Gas-concentration data have been normalized to the 0 to 1 scale on left: CO2 (squares) - 190 to 430 ppm; CH4 (triangles) - 600 to 2400 ppb; N2O (diamonds) - 280 to 340 ppb. Mean global temperature (circles) plotted relative to oC on right. Vertical dashed-line at 1995, horizontal dotted line at maximum CO2 concentration and global temperature over human history before 1990. Filled and open symbols same as in Fig. 1. Projections in short-term future are based upon continuation at current growth rates. (Data measured from graphs in Gribbin, 1990 and Khalil and Rasmussen, 1992).
----------
Mean-global-temperature (MGT) is related to the concentration of greenhouse gases (carbon dioxide, methane, nitrous oxide, water vapor and other trace gases) in the atmosphere. The most prevalent greenhouse gas is carbon dioxide (CO2). It has been shown that there is a strong relation between the atmospheric concentration of CO2 and MGT over the last 160,000 years (Gribbin, 1990). It has been suspected that the burning of fossil fuels and the clearing of land has reached such proportions that these activities have precipitated a significant increase in atmospheric CO2 concentration. The concentrations of greenhouse gases in the atmosphere have been directly measured since about 1960 and have been determined over the more distant past from air-bubbles trapped in old Antarctic, Greenland and Siberian ice and from deep-sea sediments. Mean-global-temperature has also been measured directly over the last few decades. Estimates of global temperature in the distant past have been deduced from a variety of sources. From these data, the relation among atmospheric greenhouse-gas concentrations, MGT and time is illustrated in Figure 2.
The time scale in Figure 2 is the same as that in Figure 1. Because CO2, methane (CH4) and nitrous oxide (N2O) concentrations have different scales, the data have been normalized on a 0 to 1 scale on the left. For CO2 (squares; Gribbin, 1990), 0 is equivalent to 190 parts per million (ppm) and 1 is equivalent to 430 ppm. For CH4 (triangles; R. Cicerone in Gribbin, 1990), the range is 600 to 2400 parts per billion (ppb). For N2O (diamonds; Khalil and Rasmussen, 1992), the scale is 280 to 340 ppb. Mean global temperature (circles; Gribbin, 1990) has been graphed relative to the degrees-centigrade scale on the right. The vertical dashed-line is the same as that in Figure 1. The horizontal dotted-line is the highest CO2 concentration and temperature in human history before 1990. Greenhouse-gas concentrations and MGT in the short-term future are based upon continuation at the current growth rates. This will be justified in another context below.
<Picture>Figure 3. Population and Global Warming (CO2 concentration and mean global temperature verses log-population) CO2 concentration (circles) and mean global temperature (squares) plotted relative to their absolute scales, ppm on the left and oC on the right, respectively. Vertical dashed line at 1995. (Data from Figs. 1 and 2)
----------
It is clear that the concentrations of all three gases have increased exponentially since 1950 (-1.4, Fig. 2) and that MGT has done so since 1975. Carbon dioxide concentration began to rise in conjunction with the use of fossil fuels after 1850. Although methane comes from a variety of sources, including plant decay, termites and bovine flatulence, CH4 concentration rises at the same time as CO2. This is probably due to its association with fossil-fuel production. Nitrous oxide concentration does not begin to rise until 1950. At this time, the use of human-made fertilizers and internal-combustion-engine exhaust increased dramatically. Ten thousand years ago (-4, Fig. 2), MGT increased substantially just as the agricultural revolution got started. Over the previous 200,000 years, the ecosystem was dominated by ice-ages. Projected MGT in 2025 (1.7, Fig. 2) is about 17oC, 1.5oC higher than in human history prior to 1990.
POPULATION AND GLOBAL TEMPERATURE
We have seen in Figures 1 and 2 that recent population, atmospheric greenhouse-gas concentrations and MGT have grown exponentially over about the same time-course. The relation of CO2 and MGT relative to population size can be observed by graphing these variables as above. Figure 3 shows this graph, where the log of population replaces log-time and CO2 concentration (circles) and MGT (squares) are plotted relative to their absolute scales, ppm on the left and oC on the right, respectively. The vertical dashed-line denotes 1995, as in Figures 1 and 2. When the population reached 4 billion in 1975, the converging relation between population and the other two variables becomes apparent.
The magnitude of the relations in Figures 2 and 3 can be determined by calculating the correlation coefficient between pairs of variables. Table 1 lists these coefficients for the population, greenhouse-gas concentration and MGT variables that we have been examining. The coefficients for the relations during the industrial revolution, 1800 through 1994, are above the diagonal of the table. The coefficients since 2000 years ago through 1994 are below the diagonal. Over the past 2000 years, there is a nearly perfect correlation between the concentration of greenhouse gases and population and between the greenhouse gases themselves. However, the correlations between both population and greenhouse-gas concentrations and MGT (bottom row) are not as strong. After 1800, the latter correlations increase to near perfection (rightmost column). The conclusion from the graphs and table is that there is a strong relationship among population size since 1800, greenhouse-gas concentrations and MGT.
TABLE 1. Correlation coefficients among population size, atmospheric greenhouse-gas concentrations and mean global temperature (1800 through 1994 above the top-left to bottom-right diagonal, n=10; 2000 years ago through 1994 below the diagonal, n=15).
Pop CO2 CH4 N2O Temp
----------
Pop .996 .984 .977 .916
CO2 .990 .994 .974 .942
CH4 .991 .992 .949 .945
N2O .959 .943 .942 .932
Temp .718 .716 .728 .829
GLOBAL WARMING AND CLIMATE
Determining that there is a strong relation between population size and global warming does not tell us what the underlying mechanisms are. However, documentation of the relationship between human activities and the release of greenhouse gases produces a strong inference that population size and global warming are closely related (Gribbin, 1990).
Forecasting the future is risky business. Growth rates for greenhouse-gas concentrations and MGT could decline from those at present due to unanticipated innovations or natural events. For example, volcanoes can spew enough ash into the atmosphere to block sunlight and temporarily reduce MGT slightly. However, short-term continued growth at current rates is probably an underestimate. Although population growth rate has slowed, the population is still growing. The dominating factor is that per-capita energy and resource consumption rates are increasing much faster than the population. This is not only due to anticipated increases in standards of living in underdeveloped countries, but also to future increases in the demand for energy in the developed countries (e.g., air conditioning) as summer temperatures rise. Since most of the energy will come from fossil fuels, at least for the next few decades, we can expect the atmospheric concentrations of greenhouse gases and MGT to rise in the short-term future at a faster rate than they have recently. As MGT rises, water vapor, another greenhouse component, will become a more and more significant factor due to increased evaporation.
Although a 1.5oC increase in MGT above where we were in 1990 (1990 to 2025 in Fig. 2) does not seem like much of a change, it is enough to precipitate major changes in climate. A 1.5oC drop in MGT from where we were in 1990, for example, would put the ecosystem on the verge of an ice-age. Already, there is a suspicion that, since 1975, the persistent El Nino is the first sign of the relation between global warming and climate (Kerr, 1994). As MGT increases further, we can expect more frequent and severe hurricanes and perpetual summertime droughts in many places, particularly in the US Midwest. Paradoxically, more intense winter storms will occur in some places and climatic conditions for agriculture will improve in some areas, such as in Russia (Gribbin, 1990; Bernard, 1993).
There has been considerable debate over the ecosystem's carrying capacity for humans. If we define that carrying capacity as the level that the ecosystem can support without changing state more than it has over the duration of human history, then Figures 2 and 3 indicate that we exceeded that capacity in 1975. This is the point in time where exponential growth began to push MGT along a path which has taken it outside the previous range. This does not necessarily mean that humans could not survive if MGT is about 2oC higher than it has ever been in their history. However, we will have to adapt to a radically different climate pattern and, if MGT goes any higher than that, there could be disastrous problems.
If MGT continues to increase beyond 2025 to 4oC above that in 1990, high-northern-latitude temperatures could be as much as 10oC higher than at the equator. The Arctic ice-cap would begin to melt and the permafrost under the tundra would start thawing out. As a consequence, a thick layer of rotting peat would contribute further to atmospheric CO2 and CH4 concentrations (Gribbin, 1990). With a number of human-made and natural positive-feedback elements in operation simultaneously, a threshold could be crossed (Meyers, 1995; Overpeck, 1996). Are these risks that we should be willing to take for the sake of short-term gains?
REFERENCES
Bernard, H. W. Jr., "Global Warming Unchecked", Indiana Univ. Press, Bloomington, 1993
Broecker, W., Science, 189:460, 1975
Deevey, E. S., Scientific American, 203:195, 1960
Gibbons, A. , Science, 262:27, 1993
Gribbin, J. , "Hothouse Earth", Grove Weidenfeld, New York, 1990
Kerr, R. A., Science, 266:544, 1994
Khalil, M. A. K. and R. A. Rasmussen, J. Geophys. Res., 97:4651, 1992
"The World Almanac", Pharos, New York, 1992 - 1995
Meyers, N. Science 269:358, 1995
Overpeck, J. T. Science, 271:1820, 1996
Post Script
After this document was written (about a 2 years ago), two books came out which provide much more detail relevant to some of these issues:
HOW MANY PEOPLE CAN THE EARTH SUPPORT? by Joel E. Cohen; Norton, 1995.
DIVIDED PLANET: THE ECOLOGY OF RICH AND POOR by Tom Athanasiou; Little Brown, 1996.
Both are superbly done and provide a much more comprehensive and up to date treatment of the population and economic topics included here.
Recent evidence (Mora et al.; SCIENCE 271:1105, 1996) indicates that the possibility of a "greenhouse runaway" on Earth is much more remote than indicated at the end of the previous version of this document. Therefore, the former apocalyptic ending has been changed. Although the data presented points to a catastrophic conclusion, this was (perhaps) an overstatement of the case.
Global Warming 2
Global Warming
The greenhouse effect, in environmental science, is a popular term for the effect that certain variable constituents of the Earth's lower atmosphere have on surface temperatures. It has been known since 1896 that Earth has been warmed by a blanket of gasses (This is called the "greenhouse effect."). The gases--water vapor (H2O), carbon dioxide (CO2), and methane (CH4)--keep ground temperatures at a global average of about 15 degrees C (60 degrees F). Without them the average would be below the freezing point of water. The gases have this effect because as incoming solar radiation strikes the surface, the surface gives off infrared radiation, or heat, that the gases trap and keep near ground level. The effect is comparable to the way in which a greenhouse traps heat, hence the term. Environmental scientists are concerned that changes in the variable contents of the atmosphere--particularly changes caused by human activities--could cause the Earth's surface to warm up to a dangerous degree. Since 1850 there has been a mean rise in global temperature of approximately 1° C (approximately 1.8° F). Even a limited rise in average surface temperature might lead to at least partial melting of the polar icecaps and hence a major rise in sea level, along with other severe environmental disturbances. An example of a runaway greenhouse effect is Earth's near-twin planetary neighbor Venus. Because of Venus's thick CO2 atmosphere, the planet's cloud-covered surface is hot enough to melt lead.
Water vapor is an important "greenhouse" gas. It is a major reason why humid regions experience less cooling at night than do dry regions,. However, variations in the atmosphere's CO2 content are what have played a major role in past climatic changes. In recent decades there has been a global increase in atmospheric CO2, largely as a result of the burning of fossil fuels. If the many other determinants of the Earth's present global climate remain more or less constant, the CO2 increase should raise the average temperature at the Earth's surface. As the atmosphere warmed, the amount of H2O would probably also increase, because warm air can contain more H2O than can cooler air. This process might go on indefinitely. On the other hand, reverse processes could develop such as increased cloud cover and increased absorption of CO2 by phytoplankton in the ocean. These would act as natural feedbacks, lowering temperatures.8
In fact, a great deal remains unknown about the cycling of carbon through the environment, and in particular about the role of oceans in this atmospheric carbon cycle. Many further uncertainties exist in greenhouse-effect studies because the temperature records being used tend to represent the warmer urban areas rather than the global environment. Beyond that, the effects of CH4, natural trace gases, and industrial pollutants--indeed, the complex interactions of all of these climate controls working together--are only beginning to be understood by workers in the environmental sciences.2
Despite such uncertainties, numerous scientists have maintained that the rise in global temperatures in the 1980s and early 1990s is a result of the greenhouse effect. A report issued in 1990 by the Intergovernmental Panel on Climate Change (IPCC), prepared by 170 scientists worldwide, further warned that the effect could continue to increase markedly. Most major Western industrial nations have pledged to stabilize or reduce their CO2 emissions during the 1990s. The U.S. pledge thus far concerns only chlorofluorocarbons (CFCs). CFCs attack the Ozone Layer and contribute thereby to the greenhouse effect, because the ozone layer protects the growth of ocean phytoplankton.
Bibliography
Bilger, B., Global Warming (1992)
Bolin, Bert, et al., The Greenhouse Effect, Climatic Change and Ecosystems (1986)
Bright, M., The Greenhouse Effect (1991)
Fisher, David E., Fire and Ice: The Greenhouse Effect, Ozone Depletion, and Nuclear Winter (1990)
Houghton, J., et al., eds., Climate Change: The IPCC Scientific Assessment (1990)
Monastersky, Richard, "Time for Action," Science News, Mar. 30, 1991
Moss, M., and Rahman, S., Climate and Man's Environment (1986)
Schneider, S. H., Global Warming (1989)
Seitz, F., Scientific Perspectives on the Greenhouse Problem (1990)
Shands, W. E., and Hoffmann, J. S., The Greenhouse Effect, Climatic Change, and U. S. Forests (1987)
Stone, P., "Forecast Cloudy," Technology Review, Feb./Mar. 1992
Weiner, Jonathan, The Next One Hundred Years: Shaping the Fate of Our Living Earth (1990)
Wuebbles, D., Primer on Greenhouse Gases (1991).
The greenhouse effect, in environmental science, is a popular term for the effect that certain variable constituents of the Earth's lower atmosphere have on surface temperatures. It has been known since 1896 that Earth has been warmed by a blanket of gasses (This is called the "greenhouse effect."). The gases--water vapor (H2O), carbon dioxide (CO2), and methane (CH4)--keep ground temperatures at a global average of about 15 degrees C (60 degrees F). Without them the average would be below the freezing point of water. The gases have this effect because as incoming solar radiation strikes the surface, the surface gives off infrared radiation, or heat, that the gases trap and keep near ground level. The effect is comparable to the way in which a greenhouse traps heat, hence the term. Environmental scientists are concerned that changes in the variable contents of the atmosphere--particularly changes caused by human activities--could cause the Earth's surface to warm up to a dangerous degree. Since 1850 there has been a mean rise in global temperature of approximately 1° C (approximately 1.8° F). Even a limited rise in average surface temperature might lead to at least partial melting of the polar icecaps and hence a major rise in sea level, along with other severe environmental disturbances. An example of a runaway greenhouse effect is Earth's near-twin planetary neighbor Venus. Because of Venus's thick CO2 atmosphere, the planet's cloud-covered surface is hot enough to melt lead.
Water vapor is an important "greenhouse" gas. It is a major reason why humid regions experience less cooling at night than do dry regions,. However, variations in the atmosphere's CO2 content are what have played a major role in past climatic changes. In recent decades there has been a global increase in atmospheric CO2, largely as a result of the burning of fossil fuels. If the many other determinants of the Earth's present global climate remain more or less constant, the CO2 increase should raise the average temperature at the Earth's surface. As the atmosphere warmed, the amount of H2O would probably also increase, because warm air can contain more H2O than can cooler air. This process might go on indefinitely. On the other hand, reverse processes could develop such as increased cloud cover and increased absorption of CO2 by phytoplankton in the ocean. These would act as natural feedbacks, lowering temperatures.8
In fact, a great deal remains unknown about the cycling of carbon through the environment, and in particular about the role of oceans in this atmospheric carbon cycle. Many further uncertainties exist in greenhouse-effect studies because the temperature records being used tend to represent the warmer urban areas rather than the global environment. Beyond that, the effects of CH4, natural trace gases, and industrial pollutants--indeed, the complex interactions of all of these climate controls working together--are only beginning to be understood by workers in the environmental sciences.2
Despite such uncertainties, numerous scientists have maintained that the rise in global temperatures in the 1980s and early 1990s is a result of the greenhouse effect. A report issued in 1990 by the Intergovernmental Panel on Climate Change (IPCC), prepared by 170 scientists worldwide, further warned that the effect could continue to increase markedly. Most major Western industrial nations have pledged to stabilize or reduce their CO2 emissions during the 1990s. The U.S. pledge thus far concerns only chlorofluorocarbons (CFCs). CFCs attack the Ozone Layer and contribute thereby to the greenhouse effect, because the ozone layer protects the growth of ocean phytoplankton.
Bibliography
Bilger, B., Global Warming (1992)
Bolin, Bert, et al., The Greenhouse Effect, Climatic Change and Ecosystems (1986)
Bright, M., The Greenhouse Effect (1991)
Fisher, David E., Fire and Ice: The Greenhouse Effect, Ozone Depletion, and Nuclear Winter (1990)
Houghton, J., et al., eds., Climate Change: The IPCC Scientific Assessment (1990)
Monastersky, Richard, "Time for Action," Science News, Mar. 30, 1991
Moss, M., and Rahman, S., Climate and Man's Environment (1986)
Schneider, S. H., Global Warming (1989)
Seitz, F., Scientific Perspectives on the Greenhouse Problem (1990)
Shands, W. E., and Hoffmann, J. S., The Greenhouse Effect, Climatic Change, and U. S. Forests (1987)
Stone, P., "Forecast Cloudy," Technology Review, Feb./Mar. 1992
Weiner, Jonathan, The Next One Hundred Years: Shaping the Fate of Our Living Earth (1990)
Wuebbles, D., Primer on Greenhouse Gases (1991).
Fluoridation of Municiple Water Supplies
Fluoride is a mineral that occurs naturally in almost all foods and water supplies. The fluoride ion comes from the element fluorine. Fluorine, the 13th most abundant element in the earth's crust, is never encountered in its free state in nature. It exists only in combination with other elements as a fluoride compound.
Fluoride is effective in preventing and reversing the early signs of tooth decay. Researchers have shown that there are several ways through which fluoride achieves its decay-preventive effects. It makes the tooth structure stronger, so teeth are more resistant to acid attacks. Acid is formed when the bacteria in plaque break down sugars and carbohydrates from the diet. Repeated acid attacks break down the tooth, which causes cavities. Fluoride also acts to repair areas in which acid attacks have already begun. The remineralization effect of fluoride is important because it reverses the early decay process as well as creating a tooth surface that is more resistant to decay.
Community water fluoridation is the adjustment of the amount of the beneficial trace element fluoride found in water to provide for the proper protection of teeth. Fluoridation has been widely utilized in this country since 1945. It does not involve adding anything to the water that is not already there, since virtually all sources of drinking water in the United States contain some fluoride. Fluoridation is a form of nutritional supplementation that is not unlike the addition of vitamins to milk, breads and fruit drinks; iodine to table salt; and both vitamins and minerals to breakfast cereals, grains and pastas.
The protection of fluoridation reaches community members in their homes, at work and at school -- simply by drinking the water. The only requirements for the implementation of fluoridation are the presence of a treatable centralized water supply and approval by appropriate decision makers.
Some people believe that there are effective alternatives to community water fluoridation as a public health measure for the prevention of tooth decay in the United States. The fact of the matter is that while other community-based methods of systemic and topical fluoride delivery (i.e. school-based fluoride mouthwash or tablet programs) have been developed over the five decades that water fluoridation has been practiced, none is as effective as community water fluoridation and none is free from financial constraints or other drawbacks. Alternatives to community water fluoridation remain useful only for populations significantly isolated from public water systems.
Nearly 145 million Americans are currently receiving the benefits of optimally fluoridated water. With the 1995 enactment of Assembly Bill 733 in California, ten states and territories in the United States now mandate fluoridation through legislation. Besides California, these include seven other states (Connecticut, Georgia, Illinois, Minnesota, Nebraska, Ohio and South Dakota), as well as the District of Columbia and Puerto Rico. Three states (South Dakota, Rhode Island and Kentucky), as well as the District of Columbia, have achieved the ultimate success with 100 percent of their treatable community water systems providing the benefits of fluoridation to their citizens.
While safety has been an issue frequently raised by those opposed to fluoridation, scientific data from peer-reviewed clinical research provide overwhelming evidence that the adjustment of fluoride levels in drinking water to the optimal level is undoubtedly safe. Hundreds of studies on fluoride metabolism have tracked the outcomes of ingested fluoride. Ingested fluoride essentially travels three metabolic pathways. It is either excreted by the kidneys, absorbed by the teeth or taken up in the skeleton.
At optimal levels fluoride has never been demonstrated to cause skeletal fluorosis or other bone problems. On the contrary, there is mounting evidence that continued exposure of individuals to low levels of fluoride, as in optimally fluoridated drinking water, results in a decrease in osteoporosis and a decrease in concurrent susceptibility to vertebral fracture. Furthermore, there is no evidence of increased morbidity or mortality from any disorder for those with lifetime exposures to optimally fluoridated drinking water.
Those opposed to water fluoridation claim that exposure to fluoridated water increases an individual's risk of suffering from several forms of cancer. Again, the overwhelming weight of scientific evidence indicates otherwise. Over 50 studies have evaluated the potential relationship of water fluoridation and cancer mortality. None found any credible evidence that exposure to water fluoridation is in any way related to an increased risk of cancer in humans. A number of national and international scientific commissions, after reviewing all of the available scientific literature, also concluded that water fluoridation was safe and that it in no way related to increased risk to humans of any form of cancer. Finally, a 1990 study of fluoridated and fluoride-deficient communities by the U.S. National Cancer Institute revealed no link between exposure of any populations to fluoridation and the incidence of many different types of cancer occurring in a 14-year period.
Mottled enamel or dental fluorosis has been claimed to be an indication of the "toxic effects of fluoridation" by those opposed to fluoridation. Technically, dental fluorosis is a developmental defect of enamel that can occur when a higher than optimal amount of fluoride is ingested at the same time as the stage of tooth development when enamel is being formed. The severity of the fluorosis is directly related to the age of the child at exposure, the type of exposure, the level of exposure, and the duration of exposure.
It is important to note that fluorosis can only occur during the period when teeth are developing. Once teeth have formed, fluorosis can no longer occur. The mildest form of dental fluorosis may appear in about 10 percent of those exposed to optimally fluoridated water. Most mild to moderate fluorosis occurs not from the ingestion of properly fluoridated water, but from the unnecessary and inappropriate prescribing of fluoride supplement tablets or drops for children in fluoridated areas and the inappropriate ingestion of large amounts of fluoride-containing toothpaste by young children not properly supervised during toothbrushing. The presence of dental fluorosis at any aesthetic level is not related to any other adverse conditions in humans, nor is there any evidence to show that dental fluorosis is a precursor to any disease or dysfunction. Mild to moderate dental fluorosis is no more a pathological condition than is having freckles.
There has never been a single valid, peer-reviewed laboratory, clinical or epidemiological study that showed that drinking water with fluoride at optimal levels caused cancer, heart disease, or any of the other multitude of diseases proclaimed by very small groups of antifluoridationists to be caused by fluoridation.
Because fluoride is so effective, those fortunate enough to be provided with fluoridated water can count on an up to 40- to 50-percent reduction in the number of dental cavities they would have experienced without fluoridation. Fluoridation is an extremely cost-effective public health measure because the technology is so simple and the fluoride so inexpensive. Studies indicate that a $100,000 investment in water fluoridation prevents 500,000 cavities. Moreover, for each dollar invested in fluoridation, over $80 in dental treatment costs are prevented, amounting to an 80:1 benefit-to-cost ratio. Few disease prevention efforts, public or private, achieve that level of return on investment.
Fluoride is effective in preventing and reversing the early signs of tooth decay. Researchers have shown that there are several ways through which fluoride achieves its decay-preventive effects. It makes the tooth structure stronger, so teeth are more resistant to acid attacks. Acid is formed when the bacteria in plaque break down sugars and carbohydrates from the diet. Repeated acid attacks break down the tooth, which causes cavities. Fluoride also acts to repair areas in which acid attacks have already begun. The remineralization effect of fluoride is important because it reverses the early decay process as well as creating a tooth surface that is more resistant to decay.
Community water fluoridation is the adjustment of the amount of the beneficial trace element fluoride found in water to provide for the proper protection of teeth. Fluoridation has been widely utilized in this country since 1945. It does not involve adding anything to the water that is not already there, since virtually all sources of drinking water in the United States contain some fluoride. Fluoridation is a form of nutritional supplementation that is not unlike the addition of vitamins to milk, breads and fruit drinks; iodine to table salt; and both vitamins and minerals to breakfast cereals, grains and pastas.
The protection of fluoridation reaches community members in their homes, at work and at school -- simply by drinking the water. The only requirements for the implementation of fluoridation are the presence of a treatable centralized water supply and approval by appropriate decision makers.
Some people believe that there are effective alternatives to community water fluoridation as a public health measure for the prevention of tooth decay in the United States. The fact of the matter is that while other community-based methods of systemic and topical fluoride delivery (i.e. school-based fluoride mouthwash or tablet programs) have been developed over the five decades that water fluoridation has been practiced, none is as effective as community water fluoridation and none is free from financial constraints or other drawbacks. Alternatives to community water fluoridation remain useful only for populations significantly isolated from public water systems.
Nearly 145 million Americans are currently receiving the benefits of optimally fluoridated water. With the 1995 enactment of Assembly Bill 733 in California, ten states and territories in the United States now mandate fluoridation through legislation. Besides California, these include seven other states (Connecticut, Georgia, Illinois, Minnesota, Nebraska, Ohio and South Dakota), as well as the District of Columbia and Puerto Rico. Three states (South Dakota, Rhode Island and Kentucky), as well as the District of Columbia, have achieved the ultimate success with 100 percent of their treatable community water systems providing the benefits of fluoridation to their citizens.
While safety has been an issue frequently raised by those opposed to fluoridation, scientific data from peer-reviewed clinical research provide overwhelming evidence that the adjustment of fluoride levels in drinking water to the optimal level is undoubtedly safe. Hundreds of studies on fluoride metabolism have tracked the outcomes of ingested fluoride. Ingested fluoride essentially travels three metabolic pathways. It is either excreted by the kidneys, absorbed by the teeth or taken up in the skeleton.
At optimal levels fluoride has never been demonstrated to cause skeletal fluorosis or other bone problems. On the contrary, there is mounting evidence that continued exposure of individuals to low levels of fluoride, as in optimally fluoridated drinking water, results in a decrease in osteoporosis and a decrease in concurrent susceptibility to vertebral fracture. Furthermore, there is no evidence of increased morbidity or mortality from any disorder for those with lifetime exposures to optimally fluoridated drinking water.
Those opposed to water fluoridation claim that exposure to fluoridated water increases an individual's risk of suffering from several forms of cancer. Again, the overwhelming weight of scientific evidence indicates otherwise. Over 50 studies have evaluated the potential relationship of water fluoridation and cancer mortality. None found any credible evidence that exposure to water fluoridation is in any way related to an increased risk of cancer in humans. A number of national and international scientific commissions, after reviewing all of the available scientific literature, also concluded that water fluoridation was safe and that it in no way related to increased risk to humans of any form of cancer. Finally, a 1990 study of fluoridated and fluoride-deficient communities by the U.S. National Cancer Institute revealed no link between exposure of any populations to fluoridation and the incidence of many different types of cancer occurring in a 14-year period.
Mottled enamel or dental fluorosis has been claimed to be an indication of the "toxic effects of fluoridation" by those opposed to fluoridation. Technically, dental fluorosis is a developmental defect of enamel that can occur when a higher than optimal amount of fluoride is ingested at the same time as the stage of tooth development when enamel is being formed. The severity of the fluorosis is directly related to the age of the child at exposure, the type of exposure, the level of exposure, and the duration of exposure.
It is important to note that fluorosis can only occur during the period when teeth are developing. Once teeth have formed, fluorosis can no longer occur. The mildest form of dental fluorosis may appear in about 10 percent of those exposed to optimally fluoridated water. Most mild to moderate fluorosis occurs not from the ingestion of properly fluoridated water, but from the unnecessary and inappropriate prescribing of fluoride supplement tablets or drops for children in fluoridated areas and the inappropriate ingestion of large amounts of fluoride-containing toothpaste by young children not properly supervised during toothbrushing. The presence of dental fluorosis at any aesthetic level is not related to any other adverse conditions in humans, nor is there any evidence to show that dental fluorosis is a precursor to any disease or dysfunction. Mild to moderate dental fluorosis is no more a pathological condition than is having freckles.
There has never been a single valid, peer-reviewed laboratory, clinical or epidemiological study that showed that drinking water with fluoride at optimal levels caused cancer, heart disease, or any of the other multitude of diseases proclaimed by very small groups of antifluoridationists to be caused by fluoridation.
Because fluoride is so effective, those fortunate enough to be provided with fluoridated water can count on an up to 40- to 50-percent reduction in the number of dental cavities they would have experienced without fluoridation. Fluoridation is an extremely cost-effective public health measure because the technology is so simple and the fluoride so inexpensive. Studies indicate that a $100,000 investment in water fluoridation prevents 500,000 cavities. Moreover, for each dollar invested in fluoridation, over $80 in dental treatment costs are prevented, amounting to an 80:1 benefit-to-cost ratio. Few disease prevention efforts, public or private, achieve that level of return on investment.
Faster Dissolved Oxygen Test Kit
page 21
Purpose
The purpose of my project is to determine if there is any significant
difference in dissolved oxygen (DO) levels as measured by the traditional
HACH(r) method or the newly developed CHEMets(r) test kit under typical field
conditions.
Hypothesis
My hypothesis is that there is no significant difference in dissolved oxygen
(DO) levels as measured by the traditional HACH(r) method or the newly
developed CHEMets(r) test kit under typical field conditions.
Review of Literature
"Ours is a watery world, and we, its dominant species, are walking sacks
of sea water. The presence of large amounts of liquid water on Earth make our
planet unique in the solar system." (Hill, 1992 p. 477)
People have recently become more concerned with preserving our earth
for future generations. Even the government pitches in to help save our earth by
enacting laws to help preserve our natural resources. There is local evidence
that improved sewage treatment means improvement in water quality.
Monitoring on a national level showed that large investments in point-source
pollution control have yielded no statistically significant pattern of improvement
in dissolved oxygen levels in water in the last 15 years. It may be that we are
only keeping up with the amount of pollution we are producing. (Knopman,
1993)
The early biosphere was not pleasant for life because the atmosphere
had low levels of oxygen. Photosynthetic bacteria consumed carbon dioxide and
produced simple sugars and oxygen which created the oxygen abundant
atmosphere in which more advanced life forms could develop. (Brown, 1994)
The mystery of how Earth's oxygen levels rose is very complex. Scientists don't
agree when or how the oxygen on earth got here, but we know we could not live
without it. (Pendick, 1993) Oxygen is crucial for humans to survive. Dissolved
oxygen is also crucial for most fish and aquatic organisms to survive. Dissolved
oxygen is for them what atmospheric oxygen is for humans. If humans have no
oxygen to breathe, they die. The same goes for fish. However, fish get their
oxygen from the water, and humans get theirs from the atmosphere. (Mitchell
and Stapp, 1992)
Different aquatic organisms need different levels of dissolved oxygen to
thrive. For example, pike and trout need medium to high levels of dissolved
oxygen. Carp and catfish are the exact opposite, needing only low levels of
dissolved oxygen. (Mitchell and Stapp, 1992 ) Low levels of dissolved oxygen
inhibit the growth of Asiatic clams. ( Belanger, 1991) In the American River, too
much dissolved oxygen resulted in mortality of salmonoid fishes. (Colt, Orwicz
and Brooks, 1991) Brood catfish, or catfish raised on fish farms, are especially
susceptible to low dissolved oxygen. Since catfish are a major food source for
many people, their production is important. (Avault, 1993)
There are two main sources of dissolved oxygen: (1) the atmosphere -
waves on lakes, rapidly moving rivers, and tumbling rivers all act to mix oxygen
from the atmosphere with water; (2) aquatic plants - algae and benthic plants
(bottom-rooted plants) deliver oxygen into the water through photosynthesis.
The solubility of all gases, including oxygen, is inversely proportional to
temperature which means that the solubility of gases goes down as the
temperature goes up, and vice versa. The concentration of dissolved oxygen
also varies directly with atmospheric pressure and atmospheric oxygen
concentration. When the atmospheric pressure or atmospheric oxygen
concentration goes up, the level of dissolved oxygen goes up. (Roskowski &
Marshall, 1993) D.H. Farmer studied the fluctuation of dissolved oxygen content
in a body of water before, during, and after a storm. During the storm, the
increased wave activity increased the dissolved oxygen content. (Farmer and
McNeil, 1993)
Turbulent flow in streams has caused most of the biocenogenesis (the
environmentally determined characteristics of an organisms) to be represented
by attached or benthic organisms. For this reason, a method of evaluating the
role of benthic organisms in the total dissolved oxygen balance was created.
Benthic plants play an important role in providing dissolved oxygen. These
plants respire oxygen through photosynthesis. Benthic plants are plants such as
cattail, bulrush, arrowhead, water lily, pond weeds, and muskgrass. (Nebel,
1990)
Many things can change the level of dissolved oxygen in a body of water.
Dissolved oxygen levels rise from morning through afternoon as a result of
photosynthesis. Photosynthesis stops at night, but animals and plants continue
to respire and consume oxygen. Water temperature and volume of water also
affect dissolved oxygen levels. Dry weather causes dissolved oxygen levels to
decrease and wet weather causes dissolved oxygen levels to increase. (Mitchell
and Stapp, 1990)
The breakdown of organic matter by bacteria decreases dissolved oxygen
in the water and yet enriches the water with plant nutrients. A reasonable
amount of breakdown is good, so the water won't become oligotrophic or nutrient
poor. But too much organic breakdown will decrease dissolved oxygen and
leave an excess of nutrients. Eutrophication is a term used to describe a body of
water in which the organic nutrients reduce the level of dissolved oxygen to such
a point that plant life is favored over animal life. Algae blooms cause excessive
organic material also. When algae die, they become a part of the organic
wastes. (Nebel, 1990) Most organic material can be broken down by
microorganisms. Microorganic biodegradation can be either aerobic or
anaerobic. Aerobic oxidation results in the further depletion of dissolved
oxygen. When dissolved oxygen in water is decreased by excessive organic
matter and ongoing degradation, the process then shifts to an anaerobic
process. Anaerobic bacteria actually flourish in the absence of oxygen. Animal
life can be permanently suppressed in this environment. (Hill, 1992)
When dissolved oxygen decreases, major shifts occur in the kinds of
aquatic organisms found in a body of water . The insects that need high levels
of dissolved oxygen are replaced by anaerobic organisms. Mayfly nymphs,
stonefly nymphs, caddisfly nymphs, and beetle larvae (all need high levels of
dissolved oxygen) are replaced by pollution tolerant worms, fly larvae, nuisance
algae, and other anaerobic organisms. (Mitchell and Stapp, 1992)
So what is a good level of dissolved oxygen? Under 4 ppm is not
good. But what about too much dissolved oxygen? ( Hidaka, Shimazu,
Kumanda, Takeda and Aramaki, 1991) "A nonlinear relationship was found
between oxygen concentration and median lethal concentrations values, with
significantly increased toxicity at the middle oxygen concentration. It was
concluded that dissolved oxygen concentration was an important environmental
factor in the assessment of photo-induced toxicity of anthracene to fish."
(McCloskey and Oris, 1991 p.145)
We have present day examples of the effects of pollution on dissolved
oxygen, which then in turn effects the ecosystem. Following are two clear
examples of the devastating effects of neglect of our ecosystem.
(1) The Chesapeake Bay. Chesapeake Bay is the largest estuary in
North America. Before the 1970s the bay was also the most productive, yielding
millions of pounds of fish and shellfish and a home for a variety of waterfowl.
Most of the food chains started with the sea grasses. Over half a million acres of
this underwater "grass" was present only a few feet beneath the surface. The
sea grass provided food, a place for spawning, shelter for young fish, and
dissolved oxygen for the fish to breath. In the early 1970s, the sea grasses
started to die. By 1980 the grasses were gone, except in the lower bay. All
animals that had depended on the grasses died accordingly. Even worse, the
bottom water did not have enough dissolved oxygen and caused large numbers
of lobsters, oysters, and fish to be suffocated. The water of the Chesapeake Bay
was very murky and cloudy. The cloudiness persisted over extended periods of
time. The reduced light was decreasing photosynthesis and the sea grass
began to die as a result. Without the photosynthesis of the sea grass, dissolved
oxygen was no longer being adequately supplied. In addition, bacterial
decomposition was consuming dissolved oxygen, thus making it unavailable to
fish and shellfish. Chesapeake Bay has been overcome by the process called
eutrophication. This is not unusual. In the past 40 years, many other ponds and
small lakes have also suffered this fate. (Nebel, 1990)
(2) The Black Sea. The polluting of the Black Sea is causing the Black
Sea to die. Over 300 rivers dump into the Black Sea a deadly mix of nitrates,
phosphorous, and oil. A local joke in Varna, Bulgaria, tells suicide cases not to
worry about drowning, since the sea's poisons will kill them first. The worst
offenders are the Danube, Dniester, and Dnieper Rivers. Waste from the
Danube River has increased at least tenfold over the past decade. Johann
Strauss Jr.'s "Blue Danube" would hardly be recognizable to the composer. Its
never blue now, instead it's always a color of pea-green or black. When the sun
hits puddles of oil, it forms rainbows on its ripples. The biggest problem is not
the poisons but the nutrients - the phosphorous and nitrogen. The entry of more
nutrients into the sea means more harmful surface algae to keep sunlight from
the seabeds, killing them and halting the production of dissolved oxygen.
(Pomfret, 1994)
Other rivers are polluted also, such as the River Borovniscica
(Yugoslavia), which is polluted with organic substances and the River Bistra,
which is polluted with inorganic substances. Also the death of the Cuyahoga
River, which burst into flames on June 22, 1969. ( Gordon and Steele, 1993)
Dissolved oxygen levels can vary even within the same stream, river, or
body of water. Outside the main current of a stream, dissolved oxygen levels
can be low. This point was graphically illustrated by biologist E.P. Pister as he
attempted to rescue an endangered species of pupfish. In his hurry to collect
more pupfish, he had placed the cages containing previous captures in eddies
away from the main current. By the time he noticed his error, a number of these
fragile creatures were already dead. (Pister, 1993)
Sometimes it's not lack of dissolved oxygen that kills the fish. Rather it
can be too much dissolved oxygen, as in the case of the American River.
Dissolved oxygen levels were considerably higher in the American River than
those reported to cause death in hatchery salmonoids due to gas bubble
disease. The source of this gas bubble disease and supersaturation in the river
was from air entrainment, solar heating, and photosynthesis. The impact of the
high dissolved oxygen levels in the hatchery water supplies was decreased with
the installation of degassing structures to remove excessive dissolved oxygen.
(Colt and Orwicz and Brooks, 1991)
As people try to solve disasters like those cited above, they need to
determine the source of the problem before they work on a solution. Sometimes
even while people are trying to clean up, there is no statistically discernible
pattern of increases in the water's dissolved oxygen content. Many companies
offer test kits to measure water quality. Some tests take a long time to run, but
people are always looking for a quicker way to run the tests especially under
field conditions where response time is critical. Some companies have come up
with a quicker way to run tests, but are they as accurate as we'd like to believe?
One type of kit for measuring dissolved oxygen is put out by
CHEMetrics. The CHEMets ampoules contain a solution of indigo carmine in
reduced (near colorless) form. When you snap the tip the ampoule fills with your
water sample and any dissolved oxygen in that sample will cause the reagent to
oxidize to a blue color. Then the ampoule is compared with the standard color
bars. A noticeable problem is that there is definitely a change in the shade of
color from 0-4 ppm, but in the higher ranges it is hard to tell any difference. For
example, 5-10 ppm seem to be the same shade of blue, and there is not even a
specific color bar for 9 ppm. There is an 8 ppm and then a 10 ppm. If you say
that the shade of blue is darker than the 8 ppm color bar but less than the 10
ppm color bar, then you could declare it 9 ppm. There is no way of saying if
something is 7.5 ppm because there is no shade of blue halfway between 7 ppm
and 8 ppm.
The HACH method takes longer, but it is easier to determine the amount
of dissolved oxygen in the water. The way you determine the amount of
dissolved oxygen in the water is by how many drops of Sodium Thiosulfate
Standard Solution you add until the sample changes from yellow to colorless.
Each drop equals one ppm of dissolved oxygen.
We need to think about accuracy, but what about safety? The HACH
method uses chemicals that are labeled with "Keep Out Of Reach Of Children.
For Laboratory Use Only. Causes Eye Burns. Do Not Ingest. May Cause Skin
Irritation." along with direction what to do if you inhale, ingest, or come into
contact with the chemical. The directions indicate the need to be very cautious
with the chemical, particularly because it isn't safe without proper use. By
contrast the CHEMets kit has no warnings like this. The obvious hazard is that
you would squeeze the glass ampoule too hard and it would break.
There are many things to take into consideration when you are selecting a
test kit , not just which one is faster. Such as quality, time, safety, expense,
accuracy and much more.
Materials
HACH(r) TESTING KIT
-Dissolved Oxygen 1 Reagent Powder Pillows
-Dissolved Oxygen 2 Reagent Powder Pillows
-Dissolved Oxygen 3 Reagent Powder Pillows
-Sodium Thiosulfate, Stabilized, Standard Solution, 0.0109N
-Bottle, Dissolved Oxygen, glass stoppered
-Bottle, square, mixing
-Clippers
-Stopper, for dissolved oxygen bottle
-Tube, measuring 5.83 mL
CHEMets(r) TESTING KIT
-Self filling ampoules for colorometric analysis
-Chart with color bars for comparison to self filling ampoules
TABLE
-Covered with newpaper and/or paper towels
WATER
-Kankakee River
-Melted snow
-Tap water
-Tap water stirred for one minute
-Roof runoff
-Fish aquarium
EQUIPMENT TO RECORD RESULTS
-Paper
-Pencil
-Clipboard
SAFETY EQUIPMENT
-Rubber gloves
-Goggles
-Rubber aprons
Procedure
HACH TESTING KIT
1) Fill Dissolved Oxygen bottle (round bottle with glass stopper) with the water to
be tested by allowing water to overflow the bottle for 2 or 3 minutes. To avoid
trapping air bubbles in the bottle, incline the bottle slightly and insert the stopper
with a quick thrust. This will force the air bubbles out. If bubbles become
trapped in the bottle in Steps 2 or 4 the sample should be discarded before
repeating the test.
2) Use the clippers to open one Dissolved Oxygen 1 Regent Powder Pillow and
one Dissolved Oxygen 2 Reagent Powder Pillow. Add the contents of each
pillow to the bottle. Stopper the bottle carefully to exclude air bubbles. Grip the
bottle and stopper firmly, shake vigorously to mix. A flocculent (floc) precipitate
will be formed. If oxygen is present in the sample, the precipitate will be
brownish orange in color. A small amount of powdered reagent may remain
stuck to the bottom of the bottle. This will not affect the test results.
3) Allow the sample to stand until the floc has settled halfway in the bottle,
leaving the upper half of the sample clear. Shake the bottle again. Again let it
stand until the upper half of the sample is clear. Note the floc will not settle in
samples with high concentrations of chloride, such as sea water. No
interference with the test results will occur as long as the sample is allowed to
stand for 4 or 5 minutes.
4) Use the clippers to open one Dissolved Oxygen 3 Reagent Powder Pillow.
Remove the stopper from the bottle and add the contents of the pillow. Carefully
restopper the bottle and shake to mix. The floc will dissolve and a yellow color
will develop if oxygen is present.
5) Fill the plastic measuring tube level full of the sample prepared in Steps 1
through 4. Pour the sample into the square mixing bottle.
6) Add the Sodium Thiosulfate Standard Solution drop by drop to the mixing
bottle, swirling to mix after each drop. Hold the dropper vertically above the
bottle and count each drop as it is added. Continue to add drops until the
sample changes from yellow to colorless.
7) Each drop used to bring about the color change in Step 6 is equal 1 mg/L of
dissolved oxygen.
CHEMets(r) TESTING KIT
1) Immerse the snapper into the sample.
2) Place a CHEMet ampoule, tapered end first into the snapper.
3) Press down on the ampoule to snap the tip.
4) Remove the ampoule from the snapper, and invert it several times, allowing
the bubble to travel from end to end to mix the contents.
5) Wait 2 minutes for a full color development.
6) Use the color chart (inside box) to determine the dissolved oxygen content by
matching the filled CHEMet ampoule with the color bars on the chart. The chart
should be illuminated from above by a strong white light. Be sure to place the
ampoule on both sides of the color bar before concluding that it gives the best
match.
Results
Location Chem Hach Temp C° difference
Kankakee River (near our dock) 10 12 2.2 -2
Kankakee River (near our dock) 10 11 3.3 -1
Kankakee River ( near our dock) 9 13 4.4 -4
Kankakee River (near our dock) 10 12 5.0 -2
Roof Runoff 4 5 5.6 -1
Kankakee River (near our dock) 10 11 5.6 -1
Tap Water 7 7 18.9 0
Snow (melted) 8 8 21.1 0
Tap Water (stirred for 1 minute) 7 8 21.1 -1
Fish Aquarium 7 7 23.3 0
Fish Aquarium 7 8 23.3 -1
Fish Aquarium 7 8 23.3 -1
Tap Water 3 1 23.3 2
Graphs
Conclusions
My conclusion is that there is a significant difference in dissolved oxygen
(DO) levels as measured by the traditional HACH(r) method or the newly
developed CHEMets(r) test kit under typical field conditions. CHEMets(r) test kits
are very hard to read, especially in the higher ranges. CHEMets(r) does not
compare well to HACH(r) in areas where dissolved oxygen is higher than 8 ppm,
and it does not measure above 10 ppm. CHEMets(r) would be fine for
temperatures of about 150C or warmer. The HACH(r) test kit is the method of
choice for field analysis because it is more reliable at all levels in providing
accurate measures of dissolved oxygen. The HACH(r) method requires more
caution in use, but actually produces significant differences in measures of
dissolved oxygen.
Statistics
Wilcoxson Matched Pairs Signed Rank Test
Data gathered in the course of performing analysis is subject to certain
random fluctuations. These fluctuations may vary in size and in many cases
make it difficult to decide whether the observed differences are due to real
differences in the sample or to simple chance. The discipline of statistics allows
one to assess the probability (the odds) that measured differences arise from
chance alone. Once one has a feel for the odds that the differences arise from
chance, one can decide to reject or conditionally accept a hypothesis based on
that data.
The statistical test being used for this study (Wilcoxson - Matched Pairs
Signed Ranks) was chosen for its computational ease and power. A
nonparametric test was chosen because there was a question about the level of
measurement (ordinal or interval) and whether or not the assumptions for a
parametric test could be met.
Procedure to apply Wilcoxson - Matched Pairs Signed Ranks test. (see
table)
1. Pair all data from each sample according to date.
2. Take the difference between each pair of measurements.
3. Rank the size of each difference paying no heed to sign (drop zero
differences - split ranks on ties)
4. Compute the sum of the rank with the less frequent sign (T).
5. Set alpha for 0.05 with a two tailed test.
6. Look up the value for T in an appropriate statistical table. (table G page 254
of Nonparametric Statistics by Sidney Sigel 1956 McGraw Hill)
7. Reject the null hypothesis (Ho) if T is equal to or less than the tabled value.
Chem Hach Temp Cº Chem - Hach Rank
7 7 23.3 0
7 7 18.9 0
8 8 21.1 0
4 5 5.6 -1 3.5
7 8 21.1 -1 3.5
7 8 23.3 -1 3.5
7 8 23.3 -1 3.5
10 11 3.3 -1 3.5
10 11 5.6 -1 3.5
3 1 23.3 2 8
10 12 5.0 -2 8
10 12 2.2 -2 8
9 13 4.4 -4 10
N= 10 (number of non zero differences)
T= 8 (sum of ranks with less frequent sign)
a = 0.05 (significance level)
Ho is rejected.
Literature Cited
APHA (1990). Standard methods for the examination of water and wastewater.
(16 ed.) New York: APHA, Inc.
Avault, J. (1993, Jul/Aug). Take care of those brood cats. Aquaculture, pp.73
Belanger, S. (1991, July). The effect of dissolved oxygen, sediment, and sewage
treatment plant discharges upon growth, survival, and density of Asiatic clams.
Hydrobiologia, pp. 113-126.
Brown, L. (1994). State of the world. London: W.W. Norton & Company. pp.42.
Colt, J. & Orwicz K. & Brooks, D. (1991, Winter). Gas supersaturation in the
American River. California Fish and Game. pp.41-50.
Hikada, Shimazu, Kumanda, Takeda, Aramaki. (1991). Studies on the
occurrence of hypoxic water mass in surface mixed layer of inner area of
Kagoshima Bay. Memoirs of the Faculty of Fisheries: Kagoshima. pp.59-81.
Have, M. (1991). Selected water-quality characteristics in the upper Mississippi
River Basin, Royalton to Hastings, Minnesota. USGS Water-Resources
Investigation. pp. 125.
Hill, J. (1992). Chemistry for changing times. (6th ed.) New York: McMillain
Publishing Co. pp. 477, 487- 489.
Knopman, D. (1993, Jan/Feb). 20 years of the clean water act. Environment.
pp.16.
McCloskey, J. & Oris, J. (1991, Dec.). Effect of water temperature and dissolved
oxygen concentration on the photo-induced toxicity of anthracene to juvenile
bluegill sunfish. Aquatic Toxicology . pp.145-156.
Nebel, B. (1990). Science: the way the world works. (3rd ed.) New Jersey:
Prentice Hall.
Pomfret, 0.J. (1994, Nov. 25). Rivers deadly to Black Sea. The Daily Journal.
pp. 20.
Roskowski, R. & Marshall, B. (1993, Jul/Aug). Gases in water. Aquaculture, pp.
70-76.
Schopf, J. (!993, May). Fossil show diversity of life. Science News pp.276.
Stapp, W. & Mitchell, M. (1992). Field manual for water quality. (6th ed.).
Michigan: Thomson - Shore Inc.
Steele, J. (1993, Oct.). The American environmental policy. American
Heritage. pp.30.
Purpose
The purpose of my project is to determine if there is any significant
difference in dissolved oxygen (DO) levels as measured by the traditional
HACH(r) method or the newly developed CHEMets(r) test kit under typical field
conditions.
Hypothesis
My hypothesis is that there is no significant difference in dissolved oxygen
(DO) levels as measured by the traditional HACH(r) method or the newly
developed CHEMets(r) test kit under typical field conditions.
Review of Literature
"Ours is a watery world, and we, its dominant species, are walking sacks
of sea water. The presence of large amounts of liquid water on Earth make our
planet unique in the solar system." (Hill, 1992 p. 477)
People have recently become more concerned with preserving our earth
for future generations. Even the government pitches in to help save our earth by
enacting laws to help preserve our natural resources. There is local evidence
that improved sewage treatment means improvement in water quality.
Monitoring on a national level showed that large investments in point-source
pollution control have yielded no statistically significant pattern of improvement
in dissolved oxygen levels in water in the last 15 years. It may be that we are
only keeping up with the amount of pollution we are producing. (Knopman,
1993)
The early biosphere was not pleasant for life because the atmosphere
had low levels of oxygen. Photosynthetic bacteria consumed carbon dioxide and
produced simple sugars and oxygen which created the oxygen abundant
atmosphere in which more advanced life forms could develop. (Brown, 1994)
The mystery of how Earth's oxygen levels rose is very complex. Scientists don't
agree when or how the oxygen on earth got here, but we know we could not live
without it. (Pendick, 1993) Oxygen is crucial for humans to survive. Dissolved
oxygen is also crucial for most fish and aquatic organisms to survive. Dissolved
oxygen is for them what atmospheric oxygen is for humans. If humans have no
oxygen to breathe, they die. The same goes for fish. However, fish get their
oxygen from the water, and humans get theirs from the atmosphere. (Mitchell
and Stapp, 1992)
Different aquatic organisms need different levels of dissolved oxygen to
thrive. For example, pike and trout need medium to high levels of dissolved
oxygen. Carp and catfish are the exact opposite, needing only low levels of
dissolved oxygen. (Mitchell and Stapp, 1992 ) Low levels of dissolved oxygen
inhibit the growth of Asiatic clams. ( Belanger, 1991) In the American River, too
much dissolved oxygen resulted in mortality of salmonoid fishes. (Colt, Orwicz
and Brooks, 1991) Brood catfish, or catfish raised on fish farms, are especially
susceptible to low dissolved oxygen. Since catfish are a major food source for
many people, their production is important. (Avault, 1993)
There are two main sources of dissolved oxygen: (1) the atmosphere -
waves on lakes, rapidly moving rivers, and tumbling rivers all act to mix oxygen
from the atmosphere with water; (2) aquatic plants - algae and benthic plants
(bottom-rooted plants) deliver oxygen into the water through photosynthesis.
The solubility of all gases, including oxygen, is inversely proportional to
temperature which means that the solubility of gases goes down as the
temperature goes up, and vice versa. The concentration of dissolved oxygen
also varies directly with atmospheric pressure and atmospheric oxygen
concentration. When the atmospheric pressure or atmospheric oxygen
concentration goes up, the level of dissolved oxygen goes up. (Roskowski &
Marshall, 1993) D.H. Farmer studied the fluctuation of dissolved oxygen content
in a body of water before, during, and after a storm. During the storm, the
increased wave activity increased the dissolved oxygen content. (Farmer and
McNeil, 1993)
Turbulent flow in streams has caused most of the biocenogenesis (the
environmentally determined characteristics of an organisms) to be represented
by attached or benthic organisms. For this reason, a method of evaluating the
role of benthic organisms in the total dissolved oxygen balance was created.
Benthic plants play an important role in providing dissolved oxygen. These
plants respire oxygen through photosynthesis. Benthic plants are plants such as
cattail, bulrush, arrowhead, water lily, pond weeds, and muskgrass. (Nebel,
1990)
Many things can change the level of dissolved oxygen in a body of water.
Dissolved oxygen levels rise from morning through afternoon as a result of
photosynthesis. Photosynthesis stops at night, but animals and plants continue
to respire and consume oxygen. Water temperature and volume of water also
affect dissolved oxygen levels. Dry weather causes dissolved oxygen levels to
decrease and wet weather causes dissolved oxygen levels to increase. (Mitchell
and Stapp, 1990)
The breakdown of organic matter by bacteria decreases dissolved oxygen
in the water and yet enriches the water with plant nutrients. A reasonable
amount of breakdown is good, so the water won't become oligotrophic or nutrient
poor. But too much organic breakdown will decrease dissolved oxygen and
leave an excess of nutrients. Eutrophication is a term used to describe a body of
water in which the organic nutrients reduce the level of dissolved oxygen to such
a point that plant life is favored over animal life. Algae blooms cause excessive
organic material also. When algae die, they become a part of the organic
wastes. (Nebel, 1990) Most organic material can be broken down by
microorganisms. Microorganic biodegradation can be either aerobic or
anaerobic. Aerobic oxidation results in the further depletion of dissolved
oxygen. When dissolved oxygen in water is decreased by excessive organic
matter and ongoing degradation, the process then shifts to an anaerobic
process. Anaerobic bacteria actually flourish in the absence of oxygen. Animal
life can be permanently suppressed in this environment. (Hill, 1992)
When dissolved oxygen decreases, major shifts occur in the kinds of
aquatic organisms found in a body of water . The insects that need high levels
of dissolved oxygen are replaced by anaerobic organisms. Mayfly nymphs,
stonefly nymphs, caddisfly nymphs, and beetle larvae (all need high levels of
dissolved oxygen) are replaced by pollution tolerant worms, fly larvae, nuisance
algae, and other anaerobic organisms. (Mitchell and Stapp, 1992)
So what is a good level of dissolved oxygen? Under 4 ppm is not
good. But what about too much dissolved oxygen? ( Hidaka, Shimazu,
Kumanda, Takeda and Aramaki, 1991) "A nonlinear relationship was found
between oxygen concentration and median lethal concentrations values, with
significantly increased toxicity at the middle oxygen concentration. It was
concluded that dissolved oxygen concentration was an important environmental
factor in the assessment of photo-induced toxicity of anthracene to fish."
(McCloskey and Oris, 1991 p.145)
We have present day examples of the effects of pollution on dissolved
oxygen, which then in turn effects the ecosystem. Following are two clear
examples of the devastating effects of neglect of our ecosystem.
(1) The Chesapeake Bay. Chesapeake Bay is the largest estuary in
North America. Before the 1970s the bay was also the most productive, yielding
millions of pounds of fish and shellfish and a home for a variety of waterfowl.
Most of the food chains started with the sea grasses. Over half a million acres of
this underwater "grass" was present only a few feet beneath the surface. The
sea grass provided food, a place for spawning, shelter for young fish, and
dissolved oxygen for the fish to breath. In the early 1970s, the sea grasses
started to die. By 1980 the grasses were gone, except in the lower bay. All
animals that had depended on the grasses died accordingly. Even worse, the
bottom water did not have enough dissolved oxygen and caused large numbers
of lobsters, oysters, and fish to be suffocated. The water of the Chesapeake Bay
was very murky and cloudy. The cloudiness persisted over extended periods of
time. The reduced light was decreasing photosynthesis and the sea grass
began to die as a result. Without the photosynthesis of the sea grass, dissolved
oxygen was no longer being adequately supplied. In addition, bacterial
decomposition was consuming dissolved oxygen, thus making it unavailable to
fish and shellfish. Chesapeake Bay has been overcome by the process called
eutrophication. This is not unusual. In the past 40 years, many other ponds and
small lakes have also suffered this fate. (Nebel, 1990)
(2) The Black Sea. The polluting of the Black Sea is causing the Black
Sea to die. Over 300 rivers dump into the Black Sea a deadly mix of nitrates,
phosphorous, and oil. A local joke in Varna, Bulgaria, tells suicide cases not to
worry about drowning, since the sea's poisons will kill them first. The worst
offenders are the Danube, Dniester, and Dnieper Rivers. Waste from the
Danube River has increased at least tenfold over the past decade. Johann
Strauss Jr.'s "Blue Danube" would hardly be recognizable to the composer. Its
never blue now, instead it's always a color of pea-green or black. When the sun
hits puddles of oil, it forms rainbows on its ripples. The biggest problem is not
the poisons but the nutrients - the phosphorous and nitrogen. The entry of more
nutrients into the sea means more harmful surface algae to keep sunlight from
the seabeds, killing them and halting the production of dissolved oxygen.
(Pomfret, 1994)
Other rivers are polluted also, such as the River Borovniscica
(Yugoslavia), which is polluted with organic substances and the River Bistra,
which is polluted with inorganic substances. Also the death of the Cuyahoga
River, which burst into flames on June 22, 1969. ( Gordon and Steele, 1993)
Dissolved oxygen levels can vary even within the same stream, river, or
body of water. Outside the main current of a stream, dissolved oxygen levels
can be low. This point was graphically illustrated by biologist E.P. Pister as he
attempted to rescue an endangered species of pupfish. In his hurry to collect
more pupfish, he had placed the cages containing previous captures in eddies
away from the main current. By the time he noticed his error, a number of these
fragile creatures were already dead. (Pister, 1993)
Sometimes it's not lack of dissolved oxygen that kills the fish. Rather it
can be too much dissolved oxygen, as in the case of the American River.
Dissolved oxygen levels were considerably higher in the American River than
those reported to cause death in hatchery salmonoids due to gas bubble
disease. The source of this gas bubble disease and supersaturation in the river
was from air entrainment, solar heating, and photosynthesis. The impact of the
high dissolved oxygen levels in the hatchery water supplies was decreased with
the installation of degassing structures to remove excessive dissolved oxygen.
(Colt and Orwicz and Brooks, 1991)
As people try to solve disasters like those cited above, they need to
determine the source of the problem before they work on a solution. Sometimes
even while people are trying to clean up, there is no statistically discernible
pattern of increases in the water's dissolved oxygen content. Many companies
offer test kits to measure water quality. Some tests take a long time to run, but
people are always looking for a quicker way to run the tests especially under
field conditions where response time is critical. Some companies have come up
with a quicker way to run tests, but are they as accurate as we'd like to believe?
One type of kit for measuring dissolved oxygen is put out by
CHEMetrics. The CHEMets ampoules contain a solution of indigo carmine in
reduced (near colorless) form. When you snap the tip the ampoule fills with your
water sample and any dissolved oxygen in that sample will cause the reagent to
oxidize to a blue color. Then the ampoule is compared with the standard color
bars. A noticeable problem is that there is definitely a change in the shade of
color from 0-4 ppm, but in the higher ranges it is hard to tell any difference. For
example, 5-10 ppm seem to be the same shade of blue, and there is not even a
specific color bar for 9 ppm. There is an 8 ppm and then a 10 ppm. If you say
that the shade of blue is darker than the 8 ppm color bar but less than the 10
ppm color bar, then you could declare it 9 ppm. There is no way of saying if
something is 7.5 ppm because there is no shade of blue halfway between 7 ppm
and 8 ppm.
The HACH method takes longer, but it is easier to determine the amount
of dissolved oxygen in the water. The way you determine the amount of
dissolved oxygen in the water is by how many drops of Sodium Thiosulfate
Standard Solution you add until the sample changes from yellow to colorless.
Each drop equals one ppm of dissolved oxygen.
We need to think about accuracy, but what about safety? The HACH
method uses chemicals that are labeled with "Keep Out Of Reach Of Children.
For Laboratory Use Only. Causes Eye Burns. Do Not Ingest. May Cause Skin
Irritation." along with direction what to do if you inhale, ingest, or come into
contact with the chemical. The directions indicate the need to be very cautious
with the chemical, particularly because it isn't safe without proper use. By
contrast the CHEMets kit has no warnings like this. The obvious hazard is that
you would squeeze the glass ampoule too hard and it would break.
There are many things to take into consideration when you are selecting a
test kit , not just which one is faster. Such as quality, time, safety, expense,
accuracy and much more.
Materials
HACH(r) TESTING KIT
-Dissolved Oxygen 1 Reagent Powder Pillows
-Dissolved Oxygen 2 Reagent Powder Pillows
-Dissolved Oxygen 3 Reagent Powder Pillows
-Sodium Thiosulfate, Stabilized, Standard Solution, 0.0109N
-Bottle, Dissolved Oxygen, glass stoppered
-Bottle, square, mixing
-Clippers
-Stopper, for dissolved oxygen bottle
-Tube, measuring 5.83 mL
CHEMets(r) TESTING KIT
-Self filling ampoules for colorometric analysis
-Chart with color bars for comparison to self filling ampoules
TABLE
-Covered with newpaper and/or paper towels
WATER
-Kankakee River
-Melted snow
-Tap water
-Tap water stirred for one minute
-Roof runoff
-Fish aquarium
EQUIPMENT TO RECORD RESULTS
-Paper
-Pencil
-Clipboard
SAFETY EQUIPMENT
-Rubber gloves
-Goggles
-Rubber aprons
Procedure
HACH TESTING KIT
1) Fill Dissolved Oxygen bottle (round bottle with glass stopper) with the water to
be tested by allowing water to overflow the bottle for 2 or 3 minutes. To avoid
trapping air bubbles in the bottle, incline the bottle slightly and insert the stopper
with a quick thrust. This will force the air bubbles out. If bubbles become
trapped in the bottle in Steps 2 or 4 the sample should be discarded before
repeating the test.
2) Use the clippers to open one Dissolved Oxygen 1 Regent Powder Pillow and
one Dissolved Oxygen 2 Reagent Powder Pillow. Add the contents of each
pillow to the bottle. Stopper the bottle carefully to exclude air bubbles. Grip the
bottle and stopper firmly, shake vigorously to mix. A flocculent (floc) precipitate
will be formed. If oxygen is present in the sample, the precipitate will be
brownish orange in color. A small amount of powdered reagent may remain
stuck to the bottom of the bottle. This will not affect the test results.
3) Allow the sample to stand until the floc has settled halfway in the bottle,
leaving the upper half of the sample clear. Shake the bottle again. Again let it
stand until the upper half of the sample is clear. Note the floc will not settle in
samples with high concentrations of chloride, such as sea water. No
interference with the test results will occur as long as the sample is allowed to
stand for 4 or 5 minutes.
4) Use the clippers to open one Dissolved Oxygen 3 Reagent Powder Pillow.
Remove the stopper from the bottle and add the contents of the pillow. Carefully
restopper the bottle and shake to mix. The floc will dissolve and a yellow color
will develop if oxygen is present.
5) Fill the plastic measuring tube level full of the sample prepared in Steps 1
through 4. Pour the sample into the square mixing bottle.
6) Add the Sodium Thiosulfate Standard Solution drop by drop to the mixing
bottle, swirling to mix after each drop. Hold the dropper vertically above the
bottle and count each drop as it is added. Continue to add drops until the
sample changes from yellow to colorless.
7) Each drop used to bring about the color change in Step 6 is equal 1 mg/L of
dissolved oxygen.
CHEMets(r) TESTING KIT
1) Immerse the snapper into the sample.
2) Place a CHEMet ampoule, tapered end first into the snapper.
3) Press down on the ampoule to snap the tip.
4) Remove the ampoule from the snapper, and invert it several times, allowing
the bubble to travel from end to end to mix the contents.
5) Wait 2 minutes for a full color development.
6) Use the color chart (inside box) to determine the dissolved oxygen content by
matching the filled CHEMet ampoule with the color bars on the chart. The chart
should be illuminated from above by a strong white light. Be sure to place the
ampoule on both sides of the color bar before concluding that it gives the best
match.
Results
Location Chem Hach Temp C° difference
Kankakee River (near our dock) 10 12 2.2 -2
Kankakee River (near our dock) 10 11 3.3 -1
Kankakee River ( near our dock) 9 13 4.4 -4
Kankakee River (near our dock) 10 12 5.0 -2
Roof Runoff 4 5 5.6 -1
Kankakee River (near our dock) 10 11 5.6 -1
Tap Water 7 7 18.9 0
Snow (melted) 8 8 21.1 0
Tap Water (stirred for 1 minute) 7 8 21.1 -1
Fish Aquarium 7 7 23.3 0
Fish Aquarium 7 8 23.3 -1
Fish Aquarium 7 8 23.3 -1
Tap Water 3 1 23.3 2
Graphs
Conclusions
My conclusion is that there is a significant difference in dissolved oxygen
(DO) levels as measured by the traditional HACH(r) method or the newly
developed CHEMets(r) test kit under typical field conditions. CHEMets(r) test kits
are very hard to read, especially in the higher ranges. CHEMets(r) does not
compare well to HACH(r) in areas where dissolved oxygen is higher than 8 ppm,
and it does not measure above 10 ppm. CHEMets(r) would be fine for
temperatures of about 150C or warmer. The HACH(r) test kit is the method of
choice for field analysis because it is more reliable at all levels in providing
accurate measures of dissolved oxygen. The HACH(r) method requires more
caution in use, but actually produces significant differences in measures of
dissolved oxygen.
Statistics
Wilcoxson Matched Pairs Signed Rank Test
Data gathered in the course of performing analysis is subject to certain
random fluctuations. These fluctuations may vary in size and in many cases
make it difficult to decide whether the observed differences are due to real
differences in the sample or to simple chance. The discipline of statistics allows
one to assess the probability (the odds) that measured differences arise from
chance alone. Once one has a feel for the odds that the differences arise from
chance, one can decide to reject or conditionally accept a hypothesis based on
that data.
The statistical test being used for this study (Wilcoxson - Matched Pairs
Signed Ranks) was chosen for its computational ease and power. A
nonparametric test was chosen because there was a question about the level of
measurement (ordinal or interval) and whether or not the assumptions for a
parametric test could be met.
Procedure to apply Wilcoxson - Matched Pairs Signed Ranks test. (see
table)
1. Pair all data from each sample according to date.
2. Take the difference between each pair of measurements.
3. Rank the size of each difference paying no heed to sign (drop zero
differences - split ranks on ties)
4. Compute the sum of the rank with the less frequent sign (T).
5. Set alpha for 0.05 with a two tailed test.
6. Look up the value for T in an appropriate statistical table. (table G page 254
of Nonparametric Statistics by Sidney Sigel 1956 McGraw Hill)
7. Reject the null hypothesis (Ho) if T is equal to or less than the tabled value.
Chem Hach Temp Cº Chem - Hach Rank
7 7 23.3 0
7 7 18.9 0
8 8 21.1 0
4 5 5.6 -1 3.5
7 8 21.1 -1 3.5
7 8 23.3 -1 3.5
7 8 23.3 -1 3.5
10 11 3.3 -1 3.5
10 11 5.6 -1 3.5
3 1 23.3 2 8
10 12 5.0 -2 8
10 12 2.2 -2 8
9 13 4.4 -4 10
N= 10 (number of non zero differences)
T= 8 (sum of ranks with less frequent sign)
a = 0.05 (significance level)
Ho is rejected.
Literature Cited
APHA (1990). Standard methods for the examination of water and wastewater.
(16 ed.) New York: APHA, Inc.
Avault, J. (1993, Jul/Aug). Take care of those brood cats. Aquaculture, pp.73
Belanger, S. (1991, July). The effect of dissolved oxygen, sediment, and sewage
treatment plant discharges upon growth, survival, and density of Asiatic clams.
Hydrobiologia, pp. 113-126.
Brown, L. (1994). State of the world. London: W.W. Norton & Company. pp.42.
Colt, J. & Orwicz K. & Brooks, D. (1991, Winter). Gas supersaturation in the
American River. California Fish and Game. pp.41-50.
Hikada, Shimazu, Kumanda, Takeda, Aramaki. (1991). Studies on the
occurrence of hypoxic water mass in surface mixed layer of inner area of
Kagoshima Bay. Memoirs of the Faculty of Fisheries: Kagoshima. pp.59-81.
Have, M. (1991). Selected water-quality characteristics in the upper Mississippi
River Basin, Royalton to Hastings, Minnesota. USGS Water-Resources
Investigation. pp. 125.
Hill, J. (1992). Chemistry for changing times. (6th ed.) New York: McMillain
Publishing Co. pp. 477, 487- 489.
Knopman, D. (1993, Jan/Feb). 20 years of the clean water act. Environment.
pp.16.
McCloskey, J. & Oris, J. (1991, Dec.). Effect of water temperature and dissolved
oxygen concentration on the photo-induced toxicity of anthracene to juvenile
bluegill sunfish. Aquatic Toxicology . pp.145-156.
Nebel, B. (1990). Science: the way the world works. (3rd ed.) New Jersey:
Prentice Hall.
Pomfret, 0.J. (1994, Nov. 25). Rivers deadly to Black Sea. The Daily Journal.
pp. 20.
Roskowski, R. & Marshall, B. (1993, Jul/Aug). Gases in water. Aquaculture, pp.
70-76.
Schopf, J. (!993, May). Fossil show diversity of life. Science News pp.276.
Stapp, W. & Mitchell, M. (1992). Field manual for water quality. (6th ed.).
Michigan: Thomson - Shore Inc.
Steele, J. (1993, Oct.). The American environmental policy. American
Heritage. pp.30.
Evolution part 2
Human Evolution, the biological and cultural development of the species Homo sapiens, or human beings. A large number of fossil bones and teeth have been found at various places throughout Africa, Europe, and Asia. Tools of stone, bone, and wood, as well as fire hearths, campsites, and burials, also have been discovered and excavated. As a result of these discoveries, a picture of human evolution during the past 4 to 5 million years has emerged.
Human Physical Traits
Humans are classified in the mammalian order Primates; within this order, humans, along with our extinct close ancestors, and our nearest living relatives, the African apes, are sometimes placed together in the family Hominidae because of genetic similarities, although classification systems more commonly still place great apes in a separate family, Pongidae. If the single grouping, Hominidae, is used, the separate human line in the hominid family is distinguished by being placed in a subfamily, Homininae, whose members are then called hominines-the practice that is followed in this article. An examination of the fossil record of the hominines reveals several biological and behavioral trends characteristic of the hominine subfamily.
Bipedalism
Two-legged walking, or bipedalism, seems to be one of the earliest of the major hominine characteristics to have evolved. This form of locomotion led to a number of skeletal modifications in the lower spinal column, pelvis, and legs. Because these changes can be documented in fossil bone, bipedalism usually is seen as the defining trait of the subfamily Homininae.
Brain Size and Body Size
Much of the human ability to make and use tools and other objects stems from the large size and complexity of the human brain. Most modern humans have a braincase volume of between 1300 and 1500 cc (between 79.3 and 91.5 cu in). In the course of human evolution the size of the brain has more than tripled. The increase in brain size may be related to changes in hominine behavior. Over time, stone tools and other artifacts became increasingly numerous and sophisticated. Archaeological sites, too, show more intense occupation in later phases of human biological history.
In addition, the geographic areas occupied by our ancestors expanded during the course of human evolution. Earliest known from eastern and southern Africa, they began to move into the tropical and subtropical areas of Eurasia sometime after a million years ago, and into the temperate parts of these continents about 500,000 years ago. Much later (perhaps 50,000 years ago) hominines were able to cross the water barrier into Australia. Only after the appearance of modern humans did people move into the New World, some 30,000 years ago. It is likely that the increase in human brain size took place as part of a complex interrelationship that included the elaboration of tool use and toolmaking, as well as other learned skills, which permitted our ancestors to be increasingly able to live in a variety of environments.
The earliest hominine fossils show evidence of marked differences in body size, which may reflect a pattern of sexual dimorphism in our early ancestors. The bones suggest that females may have been 0.9 to 1.2 m (3 to 4 ft) in height and about 27 to 32 kg (about 60 to 70 lb) in weight, while males may have been somewhat more than 1.5 m (about 5 ft) tall, weighing about 68 kg (about 150 lb). The reasons for this body size difference are disputed, but may be related to specialized patterns of behavior in early hominine social groups. This extreme dimorphism appears to disappear gradually sometime after a million years ago.
Face and Teeth
The third major trend in hominine development is the gradual decrease in the size of the face and teeth. All the great apes are equipped with large, tusklike canine teeth that project well beyond the level of the other teeth. The earliest hominine remains possess canines that project slightly, but those of all later hominines show a marked reduction in size. Also, the chewing teeth-premolars and molars-have decreased in size over time. Associated with these changes is a gradual reduction in the size of the face and jaws. In early hominines, the face was large and positioned in front of the braincase. As the teeth became smaller and the brain expanded, the face became smaller and its position changed; thus, the relatively small face of modern humans is located below, rather than in front of, the large, expanded braincase.
Human Origins
The fossil evidence for immediate ancestors of modern humans is divided into the genera Australopithecus and Homo, and begins about 5 million years ago. The nature of the hominine evolutionary tree before that is uncertain.
Between 7 and 20 million years ago, primitive apelike animals were widely distributed on the African and, later, on the Eurasian continents. Although many fossil bones and teeth have been found, the way of life of these creatures, and their evolutionary relationships to the living apes and humans, remain matters of active debate among scientists. One of these fossil apes, known as Sivapithecus, appears to share many distinguishing features with the living Asian great ape, the orangutan, whose direct ancestor it may well be. None of these fossils, however, offers convincing evidence of being on the evolutionary line leading to the hominid family generally or to the human subfamily in particular.
Comparisons of blood proteins and the DNA of the African great apes with that of humans indicates that the line leading to modern people did not split off from that of chimpanzees and gorillas until comparatively late in evolution. Based on these comparisons, many scientists believe a reasonable time for this evolutionary split is 6 to 8 million years ago. It is, therefore, quite possible that the known hominine fossil record, which begins about 5 million years ago, extends back virtually to the beginnings of the human line. Future fossil discoveries may permit a more precise placement of the time when the direct ancestors of the modern African ape split off from those leading to modern people and human evolution can be said to begin.
Australopithecus
The fossil evidence for human evolution begins with Australopithecus. Fossils of this genus have been discovered in a number of sites in eastern and southern Africa. Dating from more than 4 million years ago (fragmentary remains are tentatively identified from about 5 million years ago), the genus seems to have become extinct about 1.5 million years ago. All the australopithecines were efficiently bipedal and therefore indisputable hominines. In details of their teeth, jaws, and brain size, however, they differ sufficiently among themselves to warrant division into four species: A. afarensis, A. africanus, A. robustus, and A. boisei.
The earliest australopithecine is A. afarensis, which lived in eastern Africa between 3 and 4 million years ago. Found in the Afar region of Ethiopia and in Tanzania, A. afarensis had a brain size a little larger than those of chimpanzees (about 400 to 500 cc/about 24 to 33.6 cu in). Some individuals possessed canine teeth somewhat more projecting than those of later hominines. No tools of any kind have been found with A. afarensis fossils.
Between about 2.5 and 3 million years ago, A. afarensis apparently evolved into a later australopithecine, A. africanus. Known primarily from sites in southern Africa, A. africanus possessed a brain similar to that of its predecessor. However, although the size of the chewing teeth remained large, the canines, instead of projecting, grew only to the level of the other teeth. As with A. afarensis, no stone tools have been found in association with A. africanus fossils.
By about 2.6 million years ago, the fossil evidence reveals the presence of at least two, and perhaps as many as four, separate species of hominines. An evolutionary split seems to have occurred in the hominine line, with one segment evolving toward the genus Homo, and finally to modern humans, and the others developing into australopithecine species that eventually became extinct. The latter include the robust australopithecines, A. robustus, limited to southern Africa, and A. boisei, found only in eastern Africa. The robust australopithecines represent a specialized adaptation because their principal difference from other australopithecines lies in the large size of their chewing teeth, jaws, and jaw muscles. The robust australopithecines became extinct about 1.5 million years ago.
The Genus Homo
Although scientists do not agree, many believe that after the evolutionary split that led to the robust australopithecines, A. africanus evolved into the genus Homo. If so, this evolutionary transition occurred between 1.5 and 2 million years ago. Fossils dating from this period display a curious mixture of traits. Some possess relatively large brains-several almost 800 cc (about 49 cu in)-and large, australopithecine-sized teeth. Others have small, Homo-sized teeth but also small, australopithecine-sized brains. A number of fossil skulls and jaws from this period, found in Tanzania and Kenya in eastern Africa, have been placed in the category H. habilis, meaning "handy man," because some of the fossils were found associated with stone tools. H. habilis possessed many traits that link it both with the earlier australopithecines and with later members of the genus Homo. It seems likely that this species represents the evolutionary transition between the australopithecines and later hominines.
The earliest evidence of stone tools comes from sites in Africa dated to about 2.5 million years ago. These tools have not been found in association with a particular hominine species. By 1.5 to 2 million years ago, sites in various parts of eastern Africa include not only many stone tools, but also animal bones with scratch marks that experiments have shown could only be left by humanlike cutting actions. These remains constitute evidence that by this time early hominines were eating meat, but whether this food was obtained by hunting or by scavenging is not known. Also unknown at present is how much of their diet came from gathered vegetable foods and insects (dietary items that do not preserve well), and how much came from animal tissue. It is also not known whether these sites represent activities by members of the line leading to Homo, or if the robust australopithecines were also making tools and eating meat.
Fossil evidence of a large-brained, small-toothed form, known earliest from north Kenya and dating from 1.5 to 1.6 million years ago, has been placed in the species H. erectus. The first part of the time span of H. erectus, like that of the earlier-in-time hominines, is limited to southern and eastern Africa. Later-between 700,000 and a million years ago-H. erectus expands into the tropical areas of the Old World, and finally at the close of its evolution, into the temperate parts of Asia. A number of archaeological sites dating from the time of H. erectus reveal a greater sophistication in toolmaking than was found at the earlier sites. At the cave site of Peking man in north China, there is evidence that fire was used; the animal fossils that have been found are sometimes of large mammals such as elephants. These data suggest that hominine behavior was becoming more complex and efficient.
Throughout the time of H. erectus the major trends in human evolution continued. The brain sizes of early H. erectus fossils are not much larger than those of previous hominines, ranging from 750 to 800 cc (45.8 to 48.8 cu in). Later H. erectus skulls possess brain sizes in the range of 1100 to 1300 cc (67.1 to 79.3 cu in), within the size variation of Homo sapiens.
Early Homo sapiens
Between 200,000 and 300,000 years ago, H. erectus evolved into H. sapiens. Because of the gradual nature of human evolution at this time, it is difficult to identify precisely when this evolutionary transition occurred, and certain fossils from this period are classified as late H. erectus by some scientists and as early H. sapiens by others.
Although placed in the same genus and species, these early H. sapiens are not identical in appearance with modern humans. New fossil evidence suggests that modern man, H. sapiens sapiens, first appeared more than 90,000 years ago. There is some disagreement among scientists on whether the hominine fossil record shows a continuous evolutionary development from the first appearance of H. sapiens to modern humans. This disagreement has especially focused on the place of Neandertals (or Neandertals), often classified as H. sapiens neanderthalis, in the chain of human evolution. The Neandertals (named for the Neander Valley in Germany, where one of the earliest skulls was found) occupied parts of Europe and the Middle East from 100,000 years ago until about 35,000 to 40,000 years ago, when they disappeared from the fossil record. Fossils of additional varieties of early H. sapiens have been discovered in other parts of the Old World.
The dispute over the Neandertals also involves the question of the evolutionary origins of modern human populations, or races. Although a precise definition of the term race is not possible (because modern humans show continuous variation from one geographic area to another), widely separate human populations are marked by a number of physical differences. The majority of these differences represent adaptations to local environmental conditions, a process that some scientists believe began with the spread of H. erectus to all parts of the Old World sometime after a million years ago. In their view, human development since H. erectus has been one continuous, in-position evolution; that is, local populations have remained, changing in appearance over time. The Neandertals and other early H. sapiens are seen as descending from H. erectus and are ancestral to modern humans.
Other scientists view racial differentiation as a relatively recent phenomenon. In their opinion, the features of the Neandertals-a low, sloping forehead, large brow ridge, and a large face without a chin-are too primitive for them to be considered the ancestors of modern humans. They place the Neandertals on a side branch of the human evolutionary tree that became extinct. According to this theory, the origins of modern humans can be found in southern Africa or the Middle East. Evolving perhaps 90,000 to 200,000 years ago, these humans then spread to all parts of the world, supplanting the local, earlier H. sapiens populations. In addition to some fragmentary fossil finds from southern Africa, support for this theory comes from comparisons of mitochondrial DNA, a DNA form inherited only from the mother, taken from women representing a worldwide distribution of ancestors. These studies suggest that humans derived from a single generation in sub-Saharan Africa or southeastern Asia. Because of the tracing through the material line, this work has come to be called the "Eve" hypothesis; its results are not accepted by most anthropologists, who consider the human race to be much older. See also RACES, CLASSIFICATION OF.
Whatever the outcome of this scientific disagreement, the evidence shows that early H. sapiens groups were highly efficient at exploiting the sometimes harsh climates of Ice Age Europe. Further, for the first time in human evolution, hominines began to bury their dead deliberately, the bodies sometimes being accompanied by stone tools, by animal bones, and even by flowers.
Modern Humans
Although the evolutionary appearance of biologically modern peoples did not dramatically change the basic pattern of adaptation that had characterized the earlier stages of human history, some innovations did take place. In addition to the first appearance of the great cave art of France and Spain See CAVE DWELLERS, some anthropologists have argued that it was during this time that human language originated, a development that would have had profound implications for all aspects of human activity. About 10,000 years ago, one of the most important events in human history took place-plants were domesticated, and soon after, animals as well. This agricultural revolution set the stage for the events in human history that eventually led to civilization.
Modern understanding of human evolution rests on known fossils, but the picture is far from complete. Only future fossil discoveries will enable scientists to fill many of the blanks in the present picture of human evolution. Employing sophisticated technological devices as well as the accumulated knowledge of the patterns of geological deposition, anthropologists are now able to pinpoint the most promising locations for fossil hunting more accurately. In the years ahead this will result in an enormous increase in the understanding of human biological history.
Daniel Mokari
Human Physical Traits
Humans are classified in the mammalian order Primates; within this order, humans, along with our extinct close ancestors, and our nearest living relatives, the African apes, are sometimes placed together in the family Hominidae because of genetic similarities, although classification systems more commonly still place great apes in a separate family, Pongidae. If the single grouping, Hominidae, is used, the separate human line in the hominid family is distinguished by being placed in a subfamily, Homininae, whose members are then called hominines-the practice that is followed in this article. An examination of the fossil record of the hominines reveals several biological and behavioral trends characteristic of the hominine subfamily.
Bipedalism
Two-legged walking, or bipedalism, seems to be one of the earliest of the major hominine characteristics to have evolved. This form of locomotion led to a number of skeletal modifications in the lower spinal column, pelvis, and legs. Because these changes can be documented in fossil bone, bipedalism usually is seen as the defining trait of the subfamily Homininae.
Brain Size and Body Size
Much of the human ability to make and use tools and other objects stems from the large size and complexity of the human brain. Most modern humans have a braincase volume of between 1300 and 1500 cc (between 79.3 and 91.5 cu in). In the course of human evolution the size of the brain has more than tripled. The increase in brain size may be related to changes in hominine behavior. Over time, stone tools and other artifacts became increasingly numerous and sophisticated. Archaeological sites, too, show more intense occupation in later phases of human biological history.
In addition, the geographic areas occupied by our ancestors expanded during the course of human evolution. Earliest known from eastern and southern Africa, they began to move into the tropical and subtropical areas of Eurasia sometime after a million years ago, and into the temperate parts of these continents about 500,000 years ago. Much later (perhaps 50,000 years ago) hominines were able to cross the water barrier into Australia. Only after the appearance of modern humans did people move into the New World, some 30,000 years ago. It is likely that the increase in human brain size took place as part of a complex interrelationship that included the elaboration of tool use and toolmaking, as well as other learned skills, which permitted our ancestors to be increasingly able to live in a variety of environments.
The earliest hominine fossils show evidence of marked differences in body size, which may reflect a pattern of sexual dimorphism in our early ancestors. The bones suggest that females may have been 0.9 to 1.2 m (3 to 4 ft) in height and about 27 to 32 kg (about 60 to 70 lb) in weight, while males may have been somewhat more than 1.5 m (about 5 ft) tall, weighing about 68 kg (about 150 lb). The reasons for this body size difference are disputed, but may be related to specialized patterns of behavior in early hominine social groups. This extreme dimorphism appears to disappear gradually sometime after a million years ago.
Face and Teeth
The third major trend in hominine development is the gradual decrease in the size of the face and teeth. All the great apes are equipped with large, tusklike canine teeth that project well beyond the level of the other teeth. The earliest hominine remains possess canines that project slightly, but those of all later hominines show a marked reduction in size. Also, the chewing teeth-premolars and molars-have decreased in size over time. Associated with these changes is a gradual reduction in the size of the face and jaws. In early hominines, the face was large and positioned in front of the braincase. As the teeth became smaller and the brain expanded, the face became smaller and its position changed; thus, the relatively small face of modern humans is located below, rather than in front of, the large, expanded braincase.
Human Origins
The fossil evidence for immediate ancestors of modern humans is divided into the genera Australopithecus and Homo, and begins about 5 million years ago. The nature of the hominine evolutionary tree before that is uncertain.
Between 7 and 20 million years ago, primitive apelike animals were widely distributed on the African and, later, on the Eurasian continents. Although many fossil bones and teeth have been found, the way of life of these creatures, and their evolutionary relationships to the living apes and humans, remain matters of active debate among scientists. One of these fossil apes, known as Sivapithecus, appears to share many distinguishing features with the living Asian great ape, the orangutan, whose direct ancestor it may well be. None of these fossils, however, offers convincing evidence of being on the evolutionary line leading to the hominid family generally or to the human subfamily in particular.
Comparisons of blood proteins and the DNA of the African great apes with that of humans indicates that the line leading to modern people did not split off from that of chimpanzees and gorillas until comparatively late in evolution. Based on these comparisons, many scientists believe a reasonable time for this evolutionary split is 6 to 8 million years ago. It is, therefore, quite possible that the known hominine fossil record, which begins about 5 million years ago, extends back virtually to the beginnings of the human line. Future fossil discoveries may permit a more precise placement of the time when the direct ancestors of the modern African ape split off from those leading to modern people and human evolution can be said to begin.
Australopithecus
The fossil evidence for human evolution begins with Australopithecus. Fossils of this genus have been discovered in a number of sites in eastern and southern Africa. Dating from more than 4 million years ago (fragmentary remains are tentatively identified from about 5 million years ago), the genus seems to have become extinct about 1.5 million years ago. All the australopithecines were efficiently bipedal and therefore indisputable hominines. In details of their teeth, jaws, and brain size, however, they differ sufficiently among themselves to warrant division into four species: A. afarensis, A. africanus, A. robustus, and A. boisei.
The earliest australopithecine is A. afarensis, which lived in eastern Africa between 3 and 4 million years ago. Found in the Afar region of Ethiopia and in Tanzania, A. afarensis had a brain size a little larger than those of chimpanzees (about 400 to 500 cc/about 24 to 33.6 cu in). Some individuals possessed canine teeth somewhat more projecting than those of later hominines. No tools of any kind have been found with A. afarensis fossils.
Between about 2.5 and 3 million years ago, A. afarensis apparently evolved into a later australopithecine, A. africanus. Known primarily from sites in southern Africa, A. africanus possessed a brain similar to that of its predecessor. However, although the size of the chewing teeth remained large, the canines, instead of projecting, grew only to the level of the other teeth. As with A. afarensis, no stone tools have been found in association with A. africanus fossils.
By about 2.6 million years ago, the fossil evidence reveals the presence of at least two, and perhaps as many as four, separate species of hominines. An evolutionary split seems to have occurred in the hominine line, with one segment evolving toward the genus Homo, and finally to modern humans, and the others developing into australopithecine species that eventually became extinct. The latter include the robust australopithecines, A. robustus, limited to southern Africa, and A. boisei, found only in eastern Africa. The robust australopithecines represent a specialized adaptation because their principal difference from other australopithecines lies in the large size of their chewing teeth, jaws, and jaw muscles. The robust australopithecines became extinct about 1.5 million years ago.
The Genus Homo
Although scientists do not agree, many believe that after the evolutionary split that led to the robust australopithecines, A. africanus evolved into the genus Homo. If so, this evolutionary transition occurred between 1.5 and 2 million years ago. Fossils dating from this period display a curious mixture of traits. Some possess relatively large brains-several almost 800 cc (about 49 cu in)-and large, australopithecine-sized teeth. Others have small, Homo-sized teeth but also small, australopithecine-sized brains. A number of fossil skulls and jaws from this period, found in Tanzania and Kenya in eastern Africa, have been placed in the category H. habilis, meaning "handy man," because some of the fossils were found associated with stone tools. H. habilis possessed many traits that link it both with the earlier australopithecines and with later members of the genus Homo. It seems likely that this species represents the evolutionary transition between the australopithecines and later hominines.
The earliest evidence of stone tools comes from sites in Africa dated to about 2.5 million years ago. These tools have not been found in association with a particular hominine species. By 1.5 to 2 million years ago, sites in various parts of eastern Africa include not only many stone tools, but also animal bones with scratch marks that experiments have shown could only be left by humanlike cutting actions. These remains constitute evidence that by this time early hominines were eating meat, but whether this food was obtained by hunting or by scavenging is not known. Also unknown at present is how much of their diet came from gathered vegetable foods and insects (dietary items that do not preserve well), and how much came from animal tissue. It is also not known whether these sites represent activities by members of the line leading to Homo, or if the robust australopithecines were also making tools and eating meat.
Fossil evidence of a large-brained, small-toothed form, known earliest from north Kenya and dating from 1.5 to 1.6 million years ago, has been placed in the species H. erectus. The first part of the time span of H. erectus, like that of the earlier-in-time hominines, is limited to southern and eastern Africa. Later-between 700,000 and a million years ago-H. erectus expands into the tropical areas of the Old World, and finally at the close of its evolution, into the temperate parts of Asia. A number of archaeological sites dating from the time of H. erectus reveal a greater sophistication in toolmaking than was found at the earlier sites. At the cave site of Peking man in north China, there is evidence that fire was used; the animal fossils that have been found are sometimes of large mammals such as elephants. These data suggest that hominine behavior was becoming more complex and efficient.
Throughout the time of H. erectus the major trends in human evolution continued. The brain sizes of early H. erectus fossils are not much larger than those of previous hominines, ranging from 750 to 800 cc (45.8 to 48.8 cu in). Later H. erectus skulls possess brain sizes in the range of 1100 to 1300 cc (67.1 to 79.3 cu in), within the size variation of Homo sapiens.
Early Homo sapiens
Between 200,000 and 300,000 years ago, H. erectus evolved into H. sapiens. Because of the gradual nature of human evolution at this time, it is difficult to identify precisely when this evolutionary transition occurred, and certain fossils from this period are classified as late H. erectus by some scientists and as early H. sapiens by others.
Although placed in the same genus and species, these early H. sapiens are not identical in appearance with modern humans. New fossil evidence suggests that modern man, H. sapiens sapiens, first appeared more than 90,000 years ago. There is some disagreement among scientists on whether the hominine fossil record shows a continuous evolutionary development from the first appearance of H. sapiens to modern humans. This disagreement has especially focused on the place of Neandertals (or Neandertals), often classified as H. sapiens neanderthalis, in the chain of human evolution. The Neandertals (named for the Neander Valley in Germany, where one of the earliest skulls was found) occupied parts of Europe and the Middle East from 100,000 years ago until about 35,000 to 40,000 years ago, when they disappeared from the fossil record. Fossils of additional varieties of early H. sapiens have been discovered in other parts of the Old World.
The dispute over the Neandertals also involves the question of the evolutionary origins of modern human populations, or races. Although a precise definition of the term race is not possible (because modern humans show continuous variation from one geographic area to another), widely separate human populations are marked by a number of physical differences. The majority of these differences represent adaptations to local environmental conditions, a process that some scientists believe began with the spread of H. erectus to all parts of the Old World sometime after a million years ago. In their view, human development since H. erectus has been one continuous, in-position evolution; that is, local populations have remained, changing in appearance over time. The Neandertals and other early H. sapiens are seen as descending from H. erectus and are ancestral to modern humans.
Other scientists view racial differentiation as a relatively recent phenomenon. In their opinion, the features of the Neandertals-a low, sloping forehead, large brow ridge, and a large face without a chin-are too primitive for them to be considered the ancestors of modern humans. They place the Neandertals on a side branch of the human evolutionary tree that became extinct. According to this theory, the origins of modern humans can be found in southern Africa or the Middle East. Evolving perhaps 90,000 to 200,000 years ago, these humans then spread to all parts of the world, supplanting the local, earlier H. sapiens populations. In addition to some fragmentary fossil finds from southern Africa, support for this theory comes from comparisons of mitochondrial DNA, a DNA form inherited only from the mother, taken from women representing a worldwide distribution of ancestors. These studies suggest that humans derived from a single generation in sub-Saharan Africa or southeastern Asia. Because of the tracing through the material line, this work has come to be called the "Eve" hypothesis; its results are not accepted by most anthropologists, who consider the human race to be much older. See also RACES, CLASSIFICATION OF.
Whatever the outcome of this scientific disagreement, the evidence shows that early H. sapiens groups were highly efficient at exploiting the sometimes harsh climates of Ice Age Europe. Further, for the first time in human evolution, hominines began to bury their dead deliberately, the bodies sometimes being accompanied by stone tools, by animal bones, and even by flowers.
Modern Humans
Although the evolutionary appearance of biologically modern peoples did not dramatically change the basic pattern of adaptation that had characterized the earlier stages of human history, some innovations did take place. In addition to the first appearance of the great cave art of France and Spain See CAVE DWELLERS, some anthropologists have argued that it was during this time that human language originated, a development that would have had profound implications for all aspects of human activity. About 10,000 years ago, one of the most important events in human history took place-plants were domesticated, and soon after, animals as well. This agricultural revolution set the stage for the events in human history that eventually led to civilization.
Modern understanding of human evolution rests on known fossils, but the picture is far from complete. Only future fossil discoveries will enable scientists to fill many of the blanks in the present picture of human evolution. Employing sophisticated technological devices as well as the accumulated knowledge of the patterns of geological deposition, anthropologists are now able to pinpoint the most promising locations for fossil hunting more accurately. In the years ahead this will result in an enormous increase in the understanding of human biological history.
Daniel Mokari
Estuaries
An estuary is a coastal area where fresh water from rivers and streams mixes with
salt water from the ocean. Many bays, sounds, and lagoons along coasts are estuaries.
Portions of rivers and streams connected to estuaries are also considered part of the
estuary. The land area from which fresh water drains into the estuary is its watershed.
Estuaries come in all shapes and sizes, each unique to their location and climate. Bays,
sounds, marshes, swamps, inlets, and sloughs are all examples of estuaries.
An estuary is a fascinating place from the largest landscape features to the smallest
microscopic organisms. When viewing an estuary from the air on is practically amazed by
dramatic river bends as freshwater finds its way back to the sea. The vast expanse of
marsh grasses or mudflats extend into calm waters that then follow the curve of an
expansive barrier beach. Wherever there are estuaries, there is a unique beauty. As rivers
meet the sea, both ocean and land contribute to an ecosystem of specialized plants and
animals.
At high tide, seawater changes estuaries, submerging the plants and flooding creeks,
marshes, panes, mudflats or mangroves, until what once was land is now water.
Throughout the tides, the days and the years, an estuary is cradled between outreaching
headlands and is buttressed on its vulnerable seaward side by fingers of sand or mud.
Estuaries transform with the tides, the incoming waters seemingly bringing back to
life organisms that have sought shelter from their temporary exposure to the non-aquatic
world. As the tides decline, organisms return to their protective postures, receding into
sediments and adjusting to changing temperatures.
The community of life found on the land and in the water includes mammals, birds,
fish, reptiles, shellfish, and plants all interacting within complex food webs. Flocks of
shore birds stilt through the shallows, lunging long bills at their abundant prey of fish,
worms, crabs or clams. Within the sediments, whether mud, sand or rocks, live billions of
microscopic bacteria, a lower level of the food web based largely on decaying plants.
Estuaries are tidally-influenced ecological systems where rivers meet the sea and
fresh water mixes with salt water. Estuaries provide habitat;tens of thousands of birds,
mammals, fish, and other wildlife depend on estuaries. They provide marine organisms,
most commercially valuable fish species included, depend on estuaries at some point
during their development. Where productivity is concerned, a healthy, untended estuary
produces from four to ten times the weight of organic matter produced by a cultivated
corn field of the same size. Estuaries provide water filtration;water draining off the
uplands carries a load of sediments and nutrients. As water flows through salt marsh peat
and the dense mesh of marsh grass blades, much of the sediment and nutrient load is
filtered out. This filtration process creates cleaner and clearer water. Estuaries also
provide flood control. Porous, resilient salt marsh soils and grasses absorb flood waters
and diffuse storm surges. Salt marsh dominated estuaries provide natural buffers between
the land and the ocean. They protect upland organisms as well as billions of dollars of
human real estate.
Estuaries are crucial transition zones between land and water that provide an
environment for lessons in biology, geology, chemistry, physics, history, and social issues.
Estuaries are significant to both marine life and people. They are critical for the survival
of fish, birds, and other wildlife because they provide safe spawning grounds and
nurseries. Marshes and other vegetation in the estuaries protect marine life and water
quality by filtering sediment and pollution. They also provide barriers against damaging
storm waves and floods.
Estuaries also have economic, recreational, and aesthetic value. People love water
sports and visit estuaries to boat, fish, swim, and just enjoy their beauty. As a result, the
economy of many coastal areas is based primarily on the natural beauty and bounty of
their estuaries. Estuaries often have ports serving shipping, transportation, and industry.
Healthy estuaries support profitable, commercial fisheries. In fact, almost 31 percent of
the Gross National Product (GNP) is produced in coastal counties. This relationship
between plants, animals, and humans makes up and estuary's ecosystem. When its
components are in balance, plant and animal life flourishes.
Humans have long been attracted to estuaries. Indian mittens consisting of shellfish
and fish bones are reminders of how ancient cultures lived. Since Colonial times we have
used estuaries and their connecting network of rivers for transporting agricultural goods
for manufacturing and trade. Not only do commercially important fish and shellfish
spawn, nurse, or feed in estuaries, estuaries also feed our hears and minds. Scientists and
even poets and painters are inspired by the beauty and diversity found in an estuary.
Human activity also seriously threatens the vulnerable ecosystems found in the
estuaries. Long considered to be wastelands, estuaries have had their channels dredged,
marshes and tidal flats filled, waters populated, and shorelines reconstructed to
accommodate our housing, transportation, and agriculture needs. As our population
grows and the demands imposed on our natural resources increase, so too does the
importance of protecting these resources for their natural and aesthetic values.
In recognition to these threats, Congress, in 1987, established the National Estuary
Program (NEP) as part of the Clean Water Act. The NEP's mission is to protect and
restore the health of estuaries while supporting economic and recreational activities. To
achieve this, the Environmental Protection Agency (EPA) helps create local NEPs by
developing partnerships between government agencies that oversee estuarine resources
and the people who depend on the estuaries for their livelihood and quality of life. These
groups plan and implement programs according to the needs of their own areas. Local
NEPs are demonstrating practical and innovative ways to revitalize and protect their
estuaries. The benefit of this program is that it brings communities together to decide the
future of their own estuaries.
One specific estuary is the San Francisco Estuary. Human activities in the 1600
square mile Bay/Delta watershed region have drastically altered natural habitats and
impaired the functions of the estuary's ecosystem. Poor cattle grazing practices contribute
to soil erosion and water quality problems. In model public or private partnership, this
NEP is assisting a private rancher in developing a grazing management strategy for a 500
acre parcel of public land within Wildcat Creek Regional Park. Strategies already being
implemented include building barriers to prevent livestock from trampling sensitive
habitats, installing pens to improvelivestock management, and selecting cattle grazing
period to retard the growth of alien and nuisance plants. These measures encourage the
regrowth of native bunchgrasses and fords that provide not only better habitat for wild
life, but also more desirable forage for the cattle. In addition, soil erosion and pollutant
loading should decrease.
Another interesting and problematic estuary is New York-New Jersey Harbor
Estuary. Trash and other foldable marine debris washing up on area beaches had been
chronic problem for the New York-New Jersey Harbor Estuary, but unusual episodes in
1987 and 1988 shocked the public and closed many beaches. The New York-New Jersey
Harbor GNP developed a short-term plan using helicopters and vessels for surveillance
and capture of the foldable debris. Along-term plan to address the floatables problem was
subsequently developed. This included the purchase of additional skimmer vessels to
collect debris, a pollution decrease strategy, and an Operation Clean Shores program in
New Jersey that has already removed 10,000 tons of debris.
There are many estuaries in the United States that are in the NEP. There are also
small estuaries. Such resources include the Mississippi and Alabama estuaries. The
GNP, National Estuary Program's basic purpose is to bring new life to present-day
estuaries.
salt water from the ocean. Many bays, sounds, and lagoons along coasts are estuaries.
Portions of rivers and streams connected to estuaries are also considered part of the
estuary. The land area from which fresh water drains into the estuary is its watershed.
Estuaries come in all shapes and sizes, each unique to their location and climate. Bays,
sounds, marshes, swamps, inlets, and sloughs are all examples of estuaries.
An estuary is a fascinating place from the largest landscape features to the smallest
microscopic organisms. When viewing an estuary from the air on is practically amazed by
dramatic river bends as freshwater finds its way back to the sea. The vast expanse of
marsh grasses or mudflats extend into calm waters that then follow the curve of an
expansive barrier beach. Wherever there are estuaries, there is a unique beauty. As rivers
meet the sea, both ocean and land contribute to an ecosystem of specialized plants and
animals.
At high tide, seawater changes estuaries, submerging the plants and flooding creeks,
marshes, panes, mudflats or mangroves, until what once was land is now water.
Throughout the tides, the days and the years, an estuary is cradled between outreaching
headlands and is buttressed on its vulnerable seaward side by fingers of sand or mud.
Estuaries transform with the tides, the incoming waters seemingly bringing back to
life organisms that have sought shelter from their temporary exposure to the non-aquatic
world. As the tides decline, organisms return to their protective postures, receding into
sediments and adjusting to changing temperatures.
The community of life found on the land and in the water includes mammals, birds,
fish, reptiles, shellfish, and plants all interacting within complex food webs. Flocks of
shore birds stilt through the shallows, lunging long bills at their abundant prey of fish,
worms, crabs or clams. Within the sediments, whether mud, sand or rocks, live billions of
microscopic bacteria, a lower level of the food web based largely on decaying plants.
Estuaries are tidally-influenced ecological systems where rivers meet the sea and
fresh water mixes with salt water. Estuaries provide habitat;tens of thousands of birds,
mammals, fish, and other wildlife depend on estuaries. They provide marine organisms,
most commercially valuable fish species included, depend on estuaries at some point
during their development. Where productivity is concerned, a healthy, untended estuary
produces from four to ten times the weight of organic matter produced by a cultivated
corn field of the same size. Estuaries provide water filtration;water draining off the
uplands carries a load of sediments and nutrients. As water flows through salt marsh peat
and the dense mesh of marsh grass blades, much of the sediment and nutrient load is
filtered out. This filtration process creates cleaner and clearer water. Estuaries also
provide flood control. Porous, resilient salt marsh soils and grasses absorb flood waters
and diffuse storm surges. Salt marsh dominated estuaries provide natural buffers between
the land and the ocean. They protect upland organisms as well as billions of dollars of
human real estate.
Estuaries are crucial transition zones between land and water that provide an
environment for lessons in biology, geology, chemistry, physics, history, and social issues.
Estuaries are significant to both marine life and people. They are critical for the survival
of fish, birds, and other wildlife because they provide safe spawning grounds and
nurseries. Marshes and other vegetation in the estuaries protect marine life and water
quality by filtering sediment and pollution. They also provide barriers against damaging
storm waves and floods.
Estuaries also have economic, recreational, and aesthetic value. People love water
sports and visit estuaries to boat, fish, swim, and just enjoy their beauty. As a result, the
economy of many coastal areas is based primarily on the natural beauty and bounty of
their estuaries. Estuaries often have ports serving shipping, transportation, and industry.
Healthy estuaries support profitable, commercial fisheries. In fact, almost 31 percent of
the Gross National Product (GNP) is produced in coastal counties. This relationship
between plants, animals, and humans makes up and estuary's ecosystem. When its
components are in balance, plant and animal life flourishes.
Humans have long been attracted to estuaries. Indian mittens consisting of shellfish
and fish bones are reminders of how ancient cultures lived. Since Colonial times we have
used estuaries and their connecting network of rivers for transporting agricultural goods
for manufacturing and trade. Not only do commercially important fish and shellfish
spawn, nurse, or feed in estuaries, estuaries also feed our hears and minds. Scientists and
even poets and painters are inspired by the beauty and diversity found in an estuary.
Human activity also seriously threatens the vulnerable ecosystems found in the
estuaries. Long considered to be wastelands, estuaries have had their channels dredged,
marshes and tidal flats filled, waters populated, and shorelines reconstructed to
accommodate our housing, transportation, and agriculture needs. As our population
grows and the demands imposed on our natural resources increase, so too does the
importance of protecting these resources for their natural and aesthetic values.
In recognition to these threats, Congress, in 1987, established the National Estuary
Program (NEP) as part of the Clean Water Act. The NEP's mission is to protect and
restore the health of estuaries while supporting economic and recreational activities. To
achieve this, the Environmental Protection Agency (EPA) helps create local NEPs by
developing partnerships between government agencies that oversee estuarine resources
and the people who depend on the estuaries for their livelihood and quality of life. These
groups plan and implement programs according to the needs of their own areas. Local
NEPs are demonstrating practical and innovative ways to revitalize and protect their
estuaries. The benefit of this program is that it brings communities together to decide the
future of their own estuaries.
One specific estuary is the San Francisco Estuary. Human activities in the 1600
square mile Bay/Delta watershed region have drastically altered natural habitats and
impaired the functions of the estuary's ecosystem. Poor cattle grazing practices contribute
to soil erosion and water quality problems. In model public or private partnership, this
NEP is assisting a private rancher in developing a grazing management strategy for a 500
acre parcel of public land within Wildcat Creek Regional Park. Strategies already being
implemented include building barriers to prevent livestock from trampling sensitive
habitats, installing pens to improvelivestock management, and selecting cattle grazing
period to retard the growth of alien and nuisance plants. These measures encourage the
regrowth of native bunchgrasses and fords that provide not only better habitat for wild
life, but also more desirable forage for the cattle. In addition, soil erosion and pollutant
loading should decrease.
Another interesting and problematic estuary is New York-New Jersey Harbor
Estuary. Trash and other foldable marine debris washing up on area beaches had been
chronic problem for the New York-New Jersey Harbor Estuary, but unusual episodes in
1987 and 1988 shocked the public and closed many beaches. The New York-New Jersey
Harbor GNP developed a short-term plan using helicopters and vessels for surveillance
and capture of the foldable debris. Along-term plan to address the floatables problem was
subsequently developed. This included the purchase of additional skimmer vessels to
collect debris, a pollution decrease strategy, and an Operation Clean Shores program in
New Jersey that has already removed 10,000 tons of debris.
There are many estuaries in the United States that are in the NEP. There are also
small estuaries. Such resources include the Mississippi and Alabama estuaries. The
GNP, National Estuary Program's basic purpose is to bring new life to present-day
estuaries.
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