Fluctuations in the range of the Sahara over the last 50 years indicate rapid response to an unstable environment. Previous studies using coarse grain tracking of vegetation between the Sahara and Sahel have reported large scale loss in the second half of the last century with some recent recovery. Fine-grain studies are now needed to examine northern fringes of the Sahel to assess whether areas with more resilient species have maintained a low level cover throughout the recent past, or if vegetation loss has been uniformly devastating. To guide conservation efforts and inform predictive climate models, such studies could also record patterns of local loss and identify refugia. Using 72 images from Landsat 5 and 7 satellites between 1984 and present, I surveyed vegetation cover across 31,000 km2 in the mountain xeric zone of mid-central Mauritania. I used two methods, Normalized Difference Vegetation Index (NDVI) and Relative Spectral Mixture Analysis (RMSA), to track vegetation change within this area.
Results/Conclusions
Preliminary analyses indicate a rapidly fluctuating vegetative cover (800 km2), disappearing locally and recently recovering, with few stable patches (300 km2). Total loss (650 km2) and new establishment (700 km2) are roughly equivalent. An analysis of relative vegetation change in 11 patches of known current vegetation density showed that sites closest to mountain areas remained stable across time while others in more open areas are declining. Sites to the south of the study area show an increasing trend in vegetation cover. These findings indicate that the majority of vegetation in this region has been in fluctuation over the last 30 years and a small fraction of the vegetation area may serve as a source for reestablishing vacated sites. It also corroborates previous research, indicating a mild recovery possibly moving northward as rain patterns have increased.
