Yunnan Lakes & Streams - A Global Ecoregion

Lake Dianchi has lost most of its endemic fish species

About the Area
The Yunnan Lakes and Streams ecoregion comprises several large, freshwater lakes situated on the Yunnan Plateau that has an average elevation of about 6,562 feet (2,000 m).

The lakes occur in deep grabens and trenches created by faulting of adjacent mountains, although they themselves are not necessarily deep as they have filled partially with alluvial sediments over time. These plateau lakes support some of the most diverse freshwater ecosystems in the entire country. For example, both Dianchi and Er Hai contain rich fish faunas and despite their location in separate river basins (Yangtze and Mekong, respectively), taxonomic similarities exceed differences.

Local Species
Dianchi historically supported 25 native fish species of which 11 are endemic (all but 2 are apparently extinct), and Er Hai supported 17 native fish species of which 9 are endemic. Other endemics in this ecoregion include aquatic plants, invertebrates, and amphibians.

Much of the plateau is built of limestone that has eroded over thousands of years to form underground caverns where at least fourteen cave fishes live. Unique species found in this ecoregion include the Yunnan firebelly newt, Shanjing crocodile newt, and the Bubble fish (the fish that inflates itself with air as a defense against predators).

Other species of interest include the Chinese giant salamander (largest salamander in the world, lives only in China and can grow to be more than 63 inches long), and the Ailao spiny toad that has 10 to16 large black spines sticking out from its upper lip, and because of this locals call it "the mustached frog." Numerous endemic fish species in the genera Cyprinus, Schizothorax, Anabarilius, and Yunnanilus occur in this ecoregion. Several lakes historically contained faunas with over half their fish species endemic.

Threats
These lakes are found in one of only two remaining subtropical forests in China on the Yunnan-Guizhou Plateau. Threats come from deforestation and destruction of habitat, silt and fertiliser runoff from intensive rice agriculture, pollution, human and industrial waste disposal, aquaculture, and fisheries. Lake Dianchi, which has lost most of its endemic fish species, is an example of a lake that has suffered heavily from sewage, industrial pollutants, and introduced species.

Resources
• NationalGeographic.com