During the twentieth century the extent of Lake Chad has fluctuated considerably as a result of cyclical drought and flooding. It has ranged from a surface area of almost 26,000 km² in June 1962 (Kindler et al. 1989) to 1,653 km² in April 1985 (Kusnir 1993). At its lowest level, the two basins have been physically separated by a dry ridge. The present lake is only a tiny remnant of the Paleo-Lake Chad, which first came into existence by tectonic subsidence 35 million years ago. There are three main types of habitat within the lake: islands of floating and rooted papyrus Cyperus papyrus and reeds Phragmites sp.and islands which are the tops of submerged dunes; extensive beds of reedmace Typha australis, papyrus and other sedges around the shore; and areas of open water. The vast populations of migrant birds at Lake Chad are sustained in part by midges, the aquatic larval stage of which (together with other zooplankton and phytoplankton) are at the base of the food chain of the abundant fish population. Some 46% of the lake and its peripheral marshes are situated within Chad.
See Box and Table 2 for key species. Waterbird counts include 61,900 wildfowl (Anatidae) in 1984. In addition, three species of the Sudan–Guinea Savanna biome occur (see Table 2).
Non-bird biodiversity: Mammals of global conservation concern that occur, or used to do so, include Loxodonta africana (EN), Tragelaphus spekei (LR/nt) and Lutra maculicollis (VU).
Pressure/threats to key biodiversity
There is currently no enforced regulation of the fishing industry of the lake and, as a result, there has been serious overfishing, including the use of nets of increasingly small mesh size. Stocks of the most important of the commercial fish species Alestes baremoze have been severely depleted since 1971. The populations of larger mammals around the lake have been affected by hunting, drought and increased competition and disturbance from domestic animals. In the dry season the exposed areas of the lake bed attract transhumant herders and their stock. Over 300,000 cattle and 100,000 sheep and goats grazed in the vicinity of the lake prior to the 1972–1975 drought. Recession cropping of sorghum on residual moisture is an important activity that annually yields an estimated 150,000 tonnes of grain. It is not known what effect, other than increased disturbance to wildlife, these activities have on the ecology of the lake. In 2000, the heads of state of the countries bordering Lake Chad declared their joint intention to reinforce protection of the lake. Efforts, supported by GEF and WWF, are under way to designate the lake as Ramsar Site in all four countries.
BirdLife International (2022) Important Bird Areas factsheet: Lake Chad. Downloaded from
http://www.birdlife.org on 30/11/2022.