Passengers board boats which will take them to Chad and islands within Lake Chad, at the port of Baga-Dogon. When the lake's waters were higher, the port was in nearby Baga where there is a paved road. The waters have now receded by about 5km and goods and people must now be ferried along a dirt track to reach the water's edge. 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.