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Carbon Cycle
All life requires carbon. However, carbon in living systems is not automatically returned to the nutrient cycle after the organism dies. Thus, the carbon has to be returned through the actions of various organism in the environment.

Carbon exists in the abiotic environment as:
carbon dioxide in the atmosphere and dissolved in water
carbonate rocks (limestone and coral - CaCO3)
deposits of coal, petroleum, and natural gas derived from biotic systems
dead organic matter (ex. humus in the soil)

Carbon initially enters the biotic world through the action of producers:
primarily photoautotrophs, like plants and algae, that use the energy of light to convert carbon dioxide to organic matter.
chemoautotrophs - bacteria and archaeans that do the same but use the energy derived from a chemical form of respiration.
Carbon returns to the Nutrient Cycle by
respiration (as CO2)
decay (producing CO2 if oxygen is present, methane if it is not)


The uptake and return of CO2 are not in balance.

There has been a general increase in the amount of carbon dioxide in the atmosphere over the last several hundred years. This phenomenon has been attributed to both the increase in pollutants emitted by human factories and by geological upheavals (such as volcanoes). However, a full discussion of this occurrence is beyond the scope of this webpage. To this end, I have provided links to sites with copious amounts of information on this topic, which can be reached here and here. The graph shows the carbon dioxide concentration at the summit of Mauna Loa in Hawaii from 1958 to 1990. The values are in parts per million. The seasonal fluctuation is caused by the increased uptake of carbon dioxide by plants in the summer.

The Greenhouse Effect

The following excerpt, designed to explain the processes and effects of global warming, was taken from the website Ozone Action, which can be reached at

          Global warming may be the greatest environmental, economic and political challenge that we face in the 21st century. Global warming is a term that describes the "greenhouse" effect. Heat from the sun enters the Earth's atmosphere and is trapped by pollutants like carbon dioxide that are emitted from burning fossil fuels. These gases absorb heat from the sun that would otherwise eventually escape from the Earth's atmosphere. Emissions of these greenhouse gases have been growing since the industrial revolution due to the burning of fossil fuels like coal, oil and gas. Therefore, an unnatural amount of heat has been trapped which has caused the Earth's surface to warm.

At stake are generations of hard work that have made America what it is today.
Scientists estimate that global warming could increase the severity of droughts, extreme weather events, increase the amount of crop killing bugs and make the temperature too hot for many crops to grow in the breadbasket of America.
Glacier National Park may melt while the Rocky Mountains could lose entire ecosystems.
Scientists estimate that sea level rise caused by global warming could put Florida's everglades under water.

The solution to global warming will require nothing less than ending our dependence on fossil fuels - a challenge that we can meet technologically within the next 30 years. The true challenge will be to convince decision makers in government and certain segments of industry to take action in opposition to the powerful oil, auto, energy and coal lobbies.