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The Xi Jiang Rivers and Streams ecoregion contains many Eurasian fish that are endemic to this ecoregion. Such diversity is unusual in a moderate climate. As the second largest river system in China, the Xi Jiang (or Pearl River) has three main tributaries: the Xi Jiang, the Beijang, and the Dongjiang. The Xi Jiang is by far the largest of the three. Numerous streams and smaller rivers feed each tributary. All these waterways are home to diverse fish species, many of which are found nowhere else on Earth.
Starting high in the Yunnan-Kweichow mountains, the Xi Jiang runs for more than 1,300 miles (2,000 km) before flowing through the vast Pearl Delta and into the South China Sea. The dramatic landscape around the Xi Jiang has inspired countless painters. Over time, different parts of the river cut through limestone to create a deep valley surrounded by low mountains. Rocky rapids, steep falls, long gorges, and caves are everywhere. Each summer monsoonal rains bring flooding to the Xi Jiang River. The level of flooding varies from year to year depending on the strength of the monsoons. Of the 300 fish species found in this ecoregion, 120 may be endemic. Migratory fish species include the rare Chinese sturgeon and two species of shad.
Over 3,000 dams have been built on the Xi Jiang and its tributaries, blocking the migrations of freshwater and anadromous species. More than 75 percent of land in the river basin has been converted to cropland, resulting in the loss of 80 percent of the original forest. This severe change in the landscape has left little natural vegetation along the rivers and streams to buffer runoff from the land. One result is water pollution due to the inflow of silt and agricultural chemicals, which harms many species. Human population in the delta of this river is expected to double over the next 25-50 years, and with an increasing population will come an increasing need for clean fresh water.
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