Estimating vegetative productivity gradients around watering points in the rangelands of Northern Senegal based on NOAA AVHRR data

Abstract

This paper tests the hypothesis that high dry season grazing pressures around watering points in rangelands in northern Senegal has a negative effect on vegetative productivity. Time series of NOAA AVHRR satellite images for three rainy seasons are used to estimate integrated NDVI (iNDVI) at a resolution of I km², and assess the dependence of iNDVI on distance to the nearest dry season water source. The observed ‘iNDVI gradients’ around watering points differ greatly between watering points and through time, leading to a rejection of the hypothesis. Possible explanations are discussed, and it is argued that iNDVI gradients are not well-suited as indicators of land degradation.

Keywords:

• Land degradation
• grazing gradients
• NOAA AVHRR NDVI
• remote sensing
• Senegal