POTENTIAL IMPACTS OF CLIMATIC-CHANGE ON NATURAL FORESTS AND FORESTRY IN BRAZILIAN AMAZONIA

Climatic change can have significant impacts on tropical forests. Of g reatest concern in Brazil is potential alteration of the hydrological cycle in Amazonia as a result of reduction in evapotranspiration that could be expected from a continuation of present deforestation trends. Other possible changes in Amazonia are more speculative, but merit re search to better assess their likelihood of occurrence and potential s everity. These include possible increased cloudiness in the northeast corner of the region (decreasing primary productivity there), increase d tree mortality throughout the region as a consequence of differentia l stimulation of vine growth by carbon dioxide (CO,) enrichment, incre ased carbon uptake by some tree species stimulated by CO, enrichment, and a variety of possible indirect effects of increased drought severi ty and frequency. Changes in temperature and rainfall as a result of g lobal warming are expected to be slight at equatorial latitudes, but s ome changes could occur. While global warming changes imply expansion of the area climatically suitable for tropical forest, human activity converting these lands to uses other than tropical forests makes it un likely that much, if any, of the potential for forest expansion would be realized. Human impacts on Brazil's Amazonian forests are great, an d can be expected to respond to changes stemming from population growt h and migration, economic activity and development policies. Some of t he human impacts on forests will be affected by climatic changes in ot her parts of Brazil and in other parts of the world. Brazil is fortuna te in having large areas of natural forest. This area, together with B razil's large area of land not currently forested that is suitable for silvicultural plantations, makes the country relatively secure in sup plying its own needs for forest products-at least through the year 205 0-despite possible erosion of forest resources by climatic change. Man y other countries are not so fortunate, and Brazil's capacity to suppl y forest products to the rest of the world is finite.