In western Africa, the Sahara desert (top, in Mauritania) blends with a loosely defined strip of transitional vegetation to the south, called the Sahel (lighter green). South of the Sahel, tropical savannas begin to dominate (darker green). This true-color <a HREF="http://modis.gsfc.nasa.gov">Moderate Resolution Imaging Spectroradiometer</a> (MODIS) image from the <a HREF="http://terra.nasa.gov/">Terra</a> satellite shows fires (red dots) burning in the Sahel in northern Senegal (left center) and Mali (right center). To the south, fires are also burning in Guinea. This image was acquired on November 9, 2002. Sensor: Terra/MODIS.