Trees recycle 50% or more of the precipitation striking rainforests through evaporation and evapotranspiration. These processes are extremely important in the hydrological cycle and in large-scale movements of water vapor, and, thus, climate stabilization. When trees are removed, there is a decrease in the amount of transpiration (the cycling of water from vegetation to soil or air and back). Since tree roots penetrate more deeply than those of grass or replacement vegetation, tree loss reduces water uptake, which still further reduces evapotranspiration. This causes a diminution of rainfall (because there is less moisture in the air), less cloud cover, and increased aridity. Temperatures become more extreme because of reduced cloud cover and because of the reduction in evapotranspiration, which has a cooling effect (similar to the cooling of one’s skin by evaporation of perspiration). In deforested areas in the Amazon, there may be an increase of as much as 40% in local annual temperatures. There is evidence that if a critical amount of rainforest is removed, such changes will be sufficient to reduce rainfall below the level required to support the remaining rainforest. It may all be reduced to arid scrub and grassland.

Share