The worlds population is increasing exponentially and is applying ever greater pressure on the resources of lakes. The exploitation of land, bodies of water, and forests from development has increased dramatically leading to a number of problems in lakes, including the collapse of their ecological systems. Changes in the natural landscape from resource extraction, the intensification of agriculture, species introductions, urbanisation, altered water balances, and hydrological regimes have all influenced the state of worlds lakes.
Of the fresh water on the found on this planet (3% of total water) 50% is contained in the natural lakes. Lake Baikal and the Great Lakes of North America represent 40% by themselves. Approximately 50% of the world's open lakes are to be found in North America. Approximately 60% of the identified closed lakes lie on the Asian continent. The closed lakes predominantly occupy the arid/semi- arid 30-50 degree Northern latitude regions The largest body of water is the Caspian Sea (380,000km ).
Lakes have a more complex and fragile ecosystem than do rivers and lack a self cleaning ability allowing them to readily accumulate pollutants. Humans depend upon lakes of all kinds and sizes for their survival and development.
A survey by the American Fisheries Society found that 30 percent of the native freshwater fish species found north of Mexico are endangered; of the endangered fish, 93 percent are affected by habitat loss. The lakes of Africa's Rift Valley contain more species than any other lakes in the world, with high levels of endemism. Lake Victoria has more than 200 endemic species, Lake Tanganyika over 140, and Lake Malawi at least 500 endemics. Pollution, introduction of nonnative species, and overfishing (for both subsistence and the international hobby-fish trade) all pose threats to these species.
In the Great Lakes system, the Nature Conservancy has identified 100 species and 31 ecological communities at risk.