Environmental Engineering Reference
In-Depth Information
Forests
A frequent major omission in the inventory of sources of carbon dioxide
is the ongoing destruction of the world's rain forests, primarily for
agricultural purposes in South America and Southeast Asia. The destruc-
tion of rain forests is an important cause of climate change. Trees are
50 percent carbon. When they are felled or burned, the carbon they
store escapes into the air as carbon dioxide. Carbon emissions from
deforestation outstrip damage caused by planes and cars and are second
only to the energy sector as a source of greenhouse gases. This is a
major world concern in terms of carbon dioxide emissions. Forests still
cover about 30 percent of the world's land area, and tropical forests
absorb about 18 percent of the carbon dioxide added by the burning
of fossil fuels, more than the emissions generated by all of the world's
cars and trucks.
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An estimated 53,000 square miles of rain forest disappear every year,
much of it in Indonesia and the Amazon Basin. Because of this, Indo-
nesia and Brazil are behind only China and the United States as green-
house gas emitters, despite the fact that neither country is noted for
heavy industry.
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Destruction of rain forests allows billions of tons of
carbon dioxide to remain in the atmosphere. The Amazon rain forest
is the largest living reservoir of carbon dioxide on the land surface. Its
trees and soil contain perhaps 150 billion tons of carbon, about 20
years' worth of humankind's emissions from burning fossil fuels. An
acre of forest stores about 200 tons of carbon through photosynthesis,
carbon that is released into the atmosphere as carbon dioxide when
the tree rots. Stopping forest destruction is diffi cult in countries where
poor farmers want more land to increase their agricultural productivity.
However, if we lose our forests, slowing climate change will be much
more diffi cult.
A related but overlooked major source of carbon dioxide is peatlands
in forested areas. Peat, formed over thousands of years from decomposed
trees, grass, and scrub, contains large amounts of carbon that used to
stay locked in the ground. When forested ground is shorn of trees in
Third World countries to create farmland, then drained by canals and
burned, carbon dioxide gushes into the atmosphere.
Deforested and formerly swampy peatlands in Indonesia in 2006
released an amount of carbon dioxide equal to the combined emis-
sions that year of Germany, Britain, and Canada, and more than U.S.
emissions from road and air travel.
