Lake Chad is a historically large, shallow lake in Africa. The lake is historically ranked as one of the largest lakes in Africa. However, its surface area varies by season as well as from year to year. Lake Chad is economically important, providing water to more than 30 million people living in the four countries surrounding it (Chad, Cameroon, Niger and Nigeria) on the edge of the Sahara.
There are many floating islands in the lake. It is home to a wide variety of wildlife, including elephants, hippopotamus, crocodile (all in decline), and large communities of migrating birds.
According to the Global Resource Information Database of the UN Environment Programme, it shrank by as much as 95% from about 1963 to 1998, but the 2007 (satellite) images show significant improvement over previous years. There is some debate over the mechanisms causing the lake's disappearance. The leading theory, which is most often cited by the UN, is that the unsustainable usage of the lake by both governments and local communities has caused the lake to be over-used, not allowing it to replenish.
Recently, however, an additional theory is gaining traction. This states that European air pollution had shifted rainfall patterns farther south, thereby making the region drier and not allowing the lake to replenish. Since the implementation of new regulations in the EU concerning air pollutants, much of this rainfall is now beginning to return, thereby explaining the small improvements observed since 2007.