GLOBAL CONSEQUENCES

Tropical rainforests play a vital role in the functioning of the planet's natural systems. The forests regulate local and global weather through their absorption and creation of rainfall and their exchange of atmospheric gases. For example, the Amazon alone creates 50-80% of its own rainfall through transpiration. Cutting the rainforests changes the reflectivity of the earth's surface, which affects global weather by altering wind and ocean current patterns, and changes rainfall distribution. If the forests continue to be destroyed, global weather patterns may become more unstable and extreme.

CLIMATIC ROLE OF FORESTS

As previously discussed, tropical rainforests play a vital role in local climate regulation by their interaction with water cycles. However, rainforests also have a significant effect on global weather. Rainforests, like all forests, affect the reflectant "shininess" of the land surface or the surface albedo. Norman Myers (1997) explains the albedo connection:

Much of the energy that converts surface moisture into water vapor comes from the sun's radiational heating of the land surface. The energy thus depends on surface albedo, or relevant degree of reflectant "shininess" of the land surface (Gash and Shuttleworth 1992). In turn, the albedo depends on the vegetation, which absorbs more heat than does bare soil. Over thick vegetation, vigorous thermal currents take moisture (provided by the same plant cover) up into the atmosphere, where it condenses as rain. Because of its influence on convection patterns and wind currents, and hence on rainfall regimes, the albedo effect constitutes a basic factor in controlling climate.

The loss of forest vegetative cover means less heat absorption translating to less moisture being taken up into the atmosphere. In the long run, this demonstrates why deforested regions experience a decline in rainfall.