干旱区生态环境知识资源中心

The ability to analyze and report changes in our environment and relate them to causative factors provides and important strategic capability to environmental decision and policy makers throughout the world. In this study, we linked changes in land cover with changes in human demographics and natural phenomena, including rainfall. The methodology presented here allows users to locate and map changes in vegetation cover over large areas quickly and inexpensively. Thus it provides policy makers with the capability to assess areas undergoing environmental change and improve their ability to positively respond or adapt to change. Morocco was used as an example and changes in vegetation cover were assessed over a twenty-three-year period (1981-2003) using 8-km Normalized Difference Vegetation Index (NDVI) data derived from the Advance Very High Resolution Radiometer (AVHRR). A regression model of NDVI over time was developed to identify long-term trends in vegetation cover for each pixel in the study area. Patches of changes in vegetation cover were identified using ArcView for visualization of specific areas. A decreasing trend in vegetation cover is an indicator of some type of stress, either natural (e.g., drought, fire) or anthropogenic (e.g., excessive grazing, urban growth), that affects that life-support function of the environment for humans. Although Morocco was the only country used in this case study, the described approach has broad application throughout the world and offers an opportunity for combating changing ecological conditions that affect populations.