Global alarm has arisen because of tropical rain forests destruction. Not only are we losing beautiful areas, but the loss also strikes deeper. Extinction of many species and changes in our global climate are effects of deforestation. If the world continues at the current rate of deforestation, the world's rainforests will be gone within 100 years-causing unknown effects to the global climate and the elimination of the majority of plant and animal species on the planet.
Deforestation occurs in many ways. The majority of rain forest cut down is cleared for agricultural use-grazing of cattle, planting of crops. Poor farmers chop down a small area (typically a few acres) and burn the tree trunks, a process called "Slash and Burn" agriculture. Intensive, or modern, agriculture occurs on a much larger scale, sometimes deforesting several square miles at a time. Large cattle pastures often replace rain forest to grow beef for the world market.
Commercial logging is another common form of deforestation, cutting trees for sale as timber or pulp. Logging can occur selectively-where only the economically valuable species are cut-or by clearcutting, where all trees are cut. Commercial logging uses heavy machinery, such as bulldozers, road graders, and log skidders, to remove cut trees and build roads. The heavy machinery is as damaging to a forest as the chainsaws are to the trees.
There are other ways in which deforestation happens, such as the building of towns and flooding caused by construction of dams. These represent only a very small fraction of total deforestation.
The actual rate of deforestation is difficult to determine and has been the focus of NASA-funded scientists for many years. NASA projects to study the deforestation of tropical forests are conducted by analyzing Satellite Imagery (pictures taken by satellites in space) to view areas of forest that have been cleared. Figure 1 shows part of a satellite scene, showing how scientists classify the landscape. There are both patches of deforestation and a "fishbone" of deforestation along roads. Forest fragments are isolated forest pieces left by deforestation, where the plants and animals are cut off from the larger forest area. Regrowth-also called secondary forest-is abandoned farmland or timber cuts that are growing back to become forest. The majority of the picture is undisturbed, or "primary," forest, with a network of rivers draining it.
The most recent figures by the Food and Agriculture Organization (FAO) estimate tropical deforestation (rain forest and other tropical forests) at 53,000 square miles per year (15.4 x 106 ha/yr) during the 1980s (FAO 1993). Of this, they estimate that 21,000 square miles (6.2 x 106 ha/yr) were deforested annually in South America, most of this in the Amazon Basin. Based on these estimates, each year an area of tropical forest large enough to cover North Carolina is deforested. Each year!
The rate of deforestation varies from region to region. Our research showed that in the Brazilian Amazon, the rate if deforestation was around 6200 square miles per year (1.8 x 106 ha/yr) from 1978-1986, but fell to 4800 sq. miles per year (1.4 x 106 ha/yr) from 1986-1993 (Skole and Tucker…