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 Aquatic EcosystemsWetland Drainage: Page 4 Until the 20th century, wetlands covered large areas in Asia, from the swampy grasslands at the base of the Himalayas to the marshes and deltas of Thailand, Cambodia and Vietnam. With the growth in human populations and pressure to raise more crops, millions of acres were filled or converted to rice paddies. Thailand has lost virtually all of its freshwater wetlands, and China, Laos and Vietnam have also incurred great losses. The majestic Sarus crane (Grus antigone) no longer nests in Thailand, and throughout Asia, cranes are threatened by loss of wetland habitat. Eight of the world's 15 crane species are found in Asia, and nearly all are considered endangered. They breed from high Tibetan reed lakes to coastal marshes, and all these habitats are being lost. The endangered black-necked crane (Grus nigricollis) breeds in high altitude sedge marshes and grasslands of the Tibetan plateau. Several of its important breeding marshes in western China have dried up as a result of intensive grazing and plowing of the steppe grasslands, and portions of its wintering wetlands in Bhutan are being drained (BI 2000). A dam planned on the Lhasa river also threatens wintering cranes. These beautiful cranes now number only 5,000 to 6,000 birds, and they are in decline (BI 2000).
Colorful Asian storks, once widespread, are now threatened with extinction as their habitat declines yearly. Seven species are now listed by BirdLife International in Threatened Birds of the World (BI 2000). They include the vulnerable milky stork (Mycteria cinerea), the endangered Storm's stork (Ciconia stormi), the vulnerable lesser adjutant (Leptoptilos javanicus), the endangered greater adjutant (Leptoptilos dubius), the endangered Oriental stork (Ciconia boyciana), the near-threatened painted stork (Mycteria leucocephala) and the near-threatened black-necked stork (Ephippiorhynchus asiaticus). Such a diversity of storks is found nowhere else on the planet. North America has only one species, the wood stork, and only the white stork is native to Europe. Some breed in the mangroves of Indonesia, and others, like the Oriental stork, which greatly resembles the white stork, winter in marshes in Japan, North Korea and Taiwan, where they face hunting, draining of wetlands, pesticides and pollution. The total world population of this bird is estimated at only 2,500 and declining (BI 2000).
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