Assessment of rangeland degradation and development of a strategy for rehabilitation

摘要

We use satellite data from different sensor systems to analyze and explain the causes, processes, and impacts of desertification in a Steppe grazing area in Syria, with the aim of supporting the formulation of a strategy for rehabilitating desertified areas. Through the mapping of parameters such as barley fields, eolian sand distribution, and drainage patterns from Thematic Mapper (TM) data, we identified barley cultivation as one major reason for increased sand erosion or its downhill deposition. With regard to the degradation of natural vegetation covers, we discriminate between climate-triggered and human-induced vegetation degradation by analyzing the natural response pattern of vegetation to rainfall. For the monitoring of vegetation covers, we used composited 10-day interval 8-km Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (NDVI) data from 1981 to 1996. A consistently changing response of vegetation to rainfall over this time period, expressed in the residuals of the NDVI{sub}(max)/Rainfall linear regression calculations, is interpreted as nonclimate or human driven, where correlations between residuals and the time of their occurrence produce correlation coefficients > |0.6|. Pixels showing a negative temporal trend in residuals coincide with areas that are most heavily used by humans. Heavily used areas were located through detecting nomadic campsites from Indian Remote Sensing Satellite (IRS)-1C data. By combining campsite distribution with census data, such as flock size, average annual offtake, and grazing habits, we assess grazing pressures and put them in relation to the natural resources. This information provided the basis for the definition of protected areas or rehabilitation plots, and for elaborating measures to support the Steppe dwellers.