GAC NDVI interannual coefficient of variation (CoV) images: ground truth sampling of the Sahel along north-south transects

While Normalized Difference Vegetation Index (NDVI) images are widely used for assessing vegetation vigour and extent, much remains to be known regard ing both how the images themselves and their interannual variation correspo nd to ground-level reality. This work addresses these issues through, a dis cussion of a series of six north-south transects in the West African Sahel. In some cases along these transects, vegetation spatial aggregation and de nsity vary directly with the NDVI coefficient of variation (CoV), while in others community dynamics confound identifying such relationships. Analysis of CoV data infers the existence of a signal for rapid, dynamic land degra dation (describable by the term 'desertification') in both the northern and southern Sahel.