Potential impacts of climatic change on natural forests and forestry in Brazilian Amazonia

Abstract

Climatic change can have significant impacts on tropical forests. Of greatest 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 research to better assess their likelihood of occurrence and potential severity. These include possible increased cloudiness in the northeast corner of the region (decreasing primary productivity there), increased tree mortality throughout the region as a consequence of differential stimulation of vine growth by carbon dioxide (CO2) enrichment, increased carbon uptake by some tree species stimulated by CO2 enrichment, and a variety of possible indirect effects of increased drought severity and frequency. Changes in temperature and rainfall as a result of global warming are expected to be slight at equatorial latitudes, but some 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 unlikely that much, if any, of the potential for forest expansion would be realized. Human impacts on Brazil's Amazonian forests are great, and can be expected to respond to changes stemming from population growth and migration, economic activity and development policies. Some of the human impacts on forests will be affected by climatic changes in other parts of Brazil and in other parts of the world. Brazil is fortunate in having large areas of natural forest. This area, together with Brazil's large area of land not currently forested that is suitable for silvicultural plantations, makes the country relatively secure in supplying its own needs for forest products-at least through the year 2050-despite possible erosion of forest resources by climatic change. Many other countries are not so fortunate, and Brazil's capacity to supply forest products to the rest of the world is finite. © 1995.