Most of Mauritania has an average rainfall of less than 300 mm, and the Sahelian region only covers the southern part of the country. In the agroecological regions of Mauritania (along the Senegal river and the southern border with Mali) vegetation recovery and increase in RUE is pronounced. Further into the drier pastoral regions no vegetation recovery has taken place. The coastal region is influenced by maritime climate, and the rainfall data is likely to be more erroneous. Milich and Weiss (2000) found erratic behavior in vegetation response to rainfall for Mauritanian rangelands (16.3 to 17.3 deg N), and suggested that failure of the seed pool to develop after dry years prevents vegetation to make use of good rains in the following years. They also suggested that animal die-back during the early 1980's drought caused a large increase in vegetation growth in the years following the drought. Milich and Weiss (2000) also emphasize small-scale variations in topography and geology to largely influence the hydrology the hence the vegetation. Click here for NPP trend map.