Climate Fact: Tanganyika Troubles

One of the most important sources of animal protein in East Africa is being threatened by rising temperatures. Over the past few decades, the average air temperature in the region around Africa’s Lake Tanganyika (which sits on the borders of Congo, Zambia, Tanzania and Burundi) has warmed by about one degree Fahrenheit. This has corresponded to an increase in the Lake’s surface temperature and a decrease in the average regional wind velocity. These trends have made the water in the Lake more stable. This means that there is less mixing, which moves nutrients around in the water and prevents them from settling on the lake bottom, where they are inaccessible to most life. The recent slow-down in water movement has resulted in a decrease in available nutrients and 20 percent decline in the total mass of phytoplankton, tiny organisms that use the sun’s energy to build bodies out of these nutrients and ultimately feed all other life in the Lake. This decline in phytoplankton mass has translated into a 30 percent decline in the fish yields that come out of the lake. Until recently, Lake Tanganyika supplied 25 to 40 percent of the animal protein consumed by the populations in the four countries it borders.

(Source: O’Reilly, CM et al. “Climate change decreases aquatic ecosystem productivity of Lake Tanganyika, Africa.” Nature 424 (2003): 766-768.)