Trees play a unique role in the global carbon cycle. They are the largest land-based natural mechanism for removing CO2 from the air. (CO2 is also removed by the oceans and ocean organisms.)
All green plants remove CO2 from the air through the photosynthesis process, converting the carbon in CO2 into cellulose plant tissue as they grow. Most plants, however, grow and die on a yearly basis - these include commercial field crops, grasses, and weeds. Only trees and shrubs continue to grow year after year, removing additional carbon from the air. Not only do trees continue to store atmospheric carbon, their large size permits them to lock up large quantities of carbon. An acre of forest will absorb about 10 times the CO2 amount absorbed by an acre of crop land or grassland. When a plant dies or is burned, the decomposition or combustion releases the carbon locked in the cellulose back into the air in the form of either CO2 or methane, CH4. Both CO2 and CH4 are greenhouse gases.
In the past, when human activities of clearing forests for agriculture and burning fossil fuels were practiced on a small scale, the earth's remaining forests could absorb most of the extra CO2 that man had produced. Today this is no longer the case, as global CO2 levels rise 0.4 percent each year, to levels not experienced on this planet for millions of years. Planting more trees and reducing timber cuts world-wide will help restore the imbalance, and buy time as ways are found to reduce world greenhouse gas emissions. ***
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