DESERTIFICATION EVALUATED USING AN INTEGRATED ENVIRONMENTAL ASSESSMENT MODEL

Desertification has been defined as land degradation in arid, semi-ari d and dry sub-humid areas resulting from various factors, including cl imatic variations and human activities (United Nations, 1992). A techn ique for identifying and assessing areas at risk for desertification i n the arid, semi-arid, and subhumid regions of the United States was d eveloped by the Desert Research Institute and the U.S. Environmental P rotection Agency (EPA), using selected environmental indicators integr ated into a Geographic Information System (GIS). Five indicators were selected: potential erosion, grazing pressure, climatic stress (expres sed as a function of changes in the Palmer Drought Severity Index [PDS I]), change in vegetation greenness (derived from the Normalized Diffe rence Vegetation Index [NDVI]), and weedy invasives as a percent of to tal plant cover. The data were integrated over a regional geographic s etting using a GIS, which facilitated data display, development and ex ploration of data relationships, including manipulation and simulation testing. By combining all five data layers, landscapes having a varyi ng risk for land degradation were identified, providing a tool which c ould be used to improve land management efficiency.