A man fixes a fishing net beside Lake Chad. With declining waters and increasing population, fish stocks have declined on Lake Chad. The lake is drying up, due largely to desertification as the Sahara advances southward. This advance is caused in part by global warming which has reduced rainfall in the region, weakening plants whose roots once held topsoil in place. The lake is also drying up because water is pumped out from the lake by government sponsored irrigation schemes.