Biological diversity in the mountains of Southwest China
The Mountains of Southwest China Hotspot stretches over 262,400 km2 of temperate to alpine mountains between the easternmost edge of the Tibetan Plateau and the Central Chinese Plain. It lies to the north of the Indo-Burma Hotspot, and to the immediate east of the Himalaya Hotspot, and is bounded in the northwest by the dry Tibetan Plateau, in the north by the Tao River of southern Gansu, and in the east by the Sichuan Basin and the plateau of eastern Yunnan.
The Mountains of Southwest China are characterized by extremely complex topography, ranging from less than 2,000 meters in some valley floors to 7,558 meters at the summit of Gongga Shan (Mountain). The mountain ridges are oriented in a generally north-south direction, perpendicular to the main Himalayan chain. The region includes the Hengduan, Gaoligong, and Nu Shan of western Yunnan; the Nyainqentanglha, Ningjing, Taniantaweng Shan, and others at the southeastern edge of the Tibetan Plateau; the Shaluli, Daxue (including Gongga Shan), Chola, and Qionglai Shan systems of Sichuan; and the Min Shan on the Sichuan-Gansu border. The Ailao Shan and Wuliang Shan of central Yunnan are not part of this hotspot (both are included in the Indo-Burma Hotspot).
The Mountains of Southwest China feed the most species-rich temperate and tropical river systems in Asia. Major river systems that traverse or originate in the hotspot include the Jingshajiang, Yalongjiang, Daduhe, and Minjiang, all branches of the Yangtze River, which empties in the East China Sea. The Lancangjiang (Mekong River), passes through Yunnan Province, Laos, Cambodia, and Vietnam on its way to the South China Sea. The Nujiang reaches the Indian Ocean through Yunnan Province and Burma.
The complex topography results in a wide range of climatic conditions. Temperatures range from frost-free throughout the year in parts of Yunnan and short, frost-free periods at the northern boundary of the region, to permanent glaciers on the high mountain peaks of Sichuan, Yunnan, and Xizang. Annual average rainfall in the region exceeds 1,000 millimeters on southwestern slopes at higher altitudes in Yunnan, while areas of the northwestern part of the region, in the rainshadow of the Tibetan Plateau, rarely receive more than 400 millimeters annually.
Climatic and topographic conditions result in a wide variety of vegetation types across the hotspot, including broad-leaved and coniferous forests, bamboo groves, scrub communities, savanna, meadow, prairie, freshwater wetlands, and alpine scrub and scree communities.
Unique and Threatened Biodiversity
As a result of the dramatic differences in topography, climate and vegetation and the physical barriers between its regions, the Mountains of Southwest China Hotspot has evolved a cluster of distinctive mini-hotspots, each with its own unique flora and fauna.
This hotspot is arguably the most botanically rich temperate region in the world, even though its species richness is not fully documented. Vascular plant diversity is estimated at about 12,000 species, representing as much as 40 percent of all the species in China. Of these, about 3,500 species (29 percent) and at least 20 genera are endemic, including about 100 endemic ferns and 20 endemic gymnosperms. Two plant families are endemic to the hotspot: the Circaeasteraceae and the monotypic Acanthochlamydaceae.
The region provides a refugium for several ancient plant species found nowhere else in the world, including representatives from the genera Rhododendron, Rhodiola, Kingdonia, and Circaeaster. More than a quarter of the world’s rhododendron species are represented in the Heng Duan Shan, an astounding 230 different species, many of which are endemic and quite rare. Some of the larger rhododendrons can grow as tall as 20 meters or more.
Of the more than 600 bird species occurring in the hotspot, only a single bird species is endemic – the white-speckled laughingthrush (Garrulax bieti, VU). Nevertheless, four Endemic Bird Areas (EBAs), identified by BirdLife International, largely overlap with the hotspot and are home to a number of restricted range and endemic species, including the Sichuan partridge (Arborophila rufipectus, EN). While species such as the white-eared pheasant (Crossoptilon crossoptilon) are not technically endemic to the hotspot, they are important species endemic to Southwest China.
The region has the richest variety of pheasants and their relatives in the world, with around 25 species in total, including Lady Amherst pheasant (Chrysolophus amherstiae). Two iridescent monal pheasants, Sclater’s monal (Lophophorus sclateri, VU) and the Chinese monal (L. lhuysii, VU), are perhaps the most brilliant.
More than 230 mammal species inhabit the hotspot, although only five are endemic, including the Gaoligong pika (Ochotona gaoligongensis) and Chinese dormouse (Dryomys sichuanensis, EN), the latter known only from the Wanglang Nature Reserve.
The giant panda (Ailuropoda melanoleuca, EN), which is almost entirely restricted to the shrinking forests of this hotspot, is the world's best-known flagship species for conservation. As with several bird species, the giant panda has a range that is not much larger than the boundaries of the hotspot. This species survives in fragmented populations confined to over 40 reserves stretching from western Sichuan to southern Gansu and southern Shaanxi. The red panda (Ailurus fulgens, EN), a smaller relative of the giant panda, is also found in this hotspot.
Other important mammal flagships include the golden monkey (Rhinopithecus roxellana, VU) and the Yunnan or black snub-nosed monkey (R. bieti, EN), which lives at higher altitudes than any other non-human primate (ranging as high as 4,500 meters). These monkeys are among the few truly temperate monkey species in the world. Several distinctive ungulate herbivores are endemic to this hotspot, including the takin (Budorcas taxicolor, VU), an unusual 300-kilogram goat antelope, the red or Bailey's goral (Nemorhaedus baileyi, VU), which is endemic to the Gaoligong Shan, and the Chinese forest musk deer (Moschus berezovskii). These herbivores provide prey for a number of large predators, including the magnificent snow leopard (Panthera uncia, EN).
Given its size and temperate climate, the Mountains of Southwest China hotspot is also home to a surprisingly wide diversity of reptiles and amphibians. There are more than 90 reptile species in the hotspot, comprising a little over 20 lizard species, and nearly 70 species of snakes. About 15 species are endemic, including the Szechwan pit viper (Trimeresurus xiangchengensis) and Kingdonward's bloodsucker (Calotes kingdonwardi).
Amphibians are represented by around 90 species in the hotspot, with the genera Scutiger, Oreolalax and Amolops being particularly well represented. Some of these species occur at very high altitudes; for example, the Xizang alpine toad (Scutiger boulengeri) is found to elevations of more than 5,000 meters above sea level. Of the eight species known to be endemic, three are threatened: Oreolalax liangbeiensis (CR), restricted to Puxiong in Yuexi County, in southern Sichuan province, from 2,850 to 3,000 meters; Scutiger gongshanensis (VU), known from Gongshan and Biluoxueshan, in northwestern Yunnan province; and Rana chevronta (CR), known from Mount Emei, in Sichuan Province, and not recorded since 1983.
The hotspot has more than 90 freshwater fish species, almost a quarter of which are endemic, including two endemic genera. The majority of fish in the hotspot are from two families, Cyprinidae and Balitoridae, while most of the endemic fish are from two genera, Schizothorax and Triplophysa.
Despite its inaccessibility due to extreme topography and climate, the Mountains of Southwest China Hotspot is still heavily impacted by human activity. High population growth rates among the inhabitants of the region and immigration from other parts of China have exacerbated the pressures on natural habitat.
Until a 1998 logging ban, one of the most serious threats to the area was intensive commercial logging. Forest cover in Sichuan Province, one of China's main sources of timber, declined from 19 percent in the 1950s to 12.6 percent in 1988. Almost all this loss was in the more remote and mountainous western part of Sichuan, since forests elsewhere in the province were cut long ago. Today, even with the ban on commercial logging, forests are still being logged at a significant rate for firewood collection and house construction, particularly in the bitterly cold high valleys of the region. In some areas, the volume of extraction for these purposes may even exceed past logging harvests.
With the exception of scree slopes and vertical cliffs, areas with no forest cover or that are unsuitable for crops are heavily impacted by large herds of grazing animals, such as yak, sheep, and goats. These animals are brought to the region by nomadic Tibetan herdsmen, who ascend to alpine pastures in the summer and return to the valleys before winter. In some cases, standing forests have been cleared to increase pasture for the growing domestic herds. Both logging and overgrazing have predictably led to serious erosion on steep slopes and to the siltation of rivers.
Emerging threats include dam building on all main rivers in the hotspot, mining, and unplanned mass tourism development, all of which are accompanied by road expansion. For example, the Chinese government has proposed the construction of eight large dams on the upper reaches of the Lancanjiang, or Mekong River, in Yunnan Province. The dams will affect sediment transport and the river's flooding cycle, and will drastically alter ecosystems both upstream and downstream of the sites. As mentioned above, this river flows through Yunnan Province, as well as Laos and Cambodia; the lives and livelihoods of millions of people living in these areas could be affected. Also, increasing access to disposable income and leisure time allows more and more Chinese citizens the opportunity to visit nature reserves and wilderness areas. Controlled tourism can provide an excellent alternative to logging and other harmful land uses; however, the construction of roads, hotels, and cable cars, along with the presence of large numbers of people in wild areas, can all lead to severe habitat degradation.
It has been calculated that the remaining forest cover totals 23 percent of Yunnan Province, 12 percent of Sichuan Province, and 5.1 percent of The Tibetan Autonomous Region (TAR) in 1992. In all, only about eight percent of the original extent of the hotspot remains in pristine condition. Since the 1980s, and particularly from the late 1990s onwards, forest regeneration has been taking place on logged sites and wasteland. This has led to an increase in overall forest cover. However, most of this increase is accounted for by monoculture plantations, including stands of alien species such as the Japanese Pine.
As in many of the hotspots in and around China, the collection of plants and animals for traditional medicinal purposes poses an enormous threat to the long-term viability of species in the Mountains of Southwest China. Among the species affected by this trade are monkeys, snakes, geckos, deer, and bears. Illegal hunting is also a major problem, and skins of protected species are frequently seen on the black market.
Conservation Action and Protected Areas
According to an analysis of protected areas in the World Database of Protected Areas, protected areas in the hotspot cover some 14,000 km2 (or 5.3 percent of the area). This coverage drops dramatically, to 1.4 percent of the hotspot, when one considers only those classed in IUCN categories I-IV. Among the best-known and most important protected areas in the hotspot is the 2,000-km2 Wolong Nature Reserve in western Sichuan, which is home to the giant panda, and around 4,000 plant species, including the Chinese yew (Taxus chinensis).
Emei Shan, an isolated and protected limestone mountain on the eastern edge of the hotspot, rises to 3,099 meters and is considered to be one of the botanically richest and most diverse mountains in the Northern Hemisphere. The mountain is one of the few places where the Tibetan macaque (Macaca thibetana) can easily be seen. Emei Shan Natural and Historical Heritage Reserve is also the only known site for two threatened amphibians: the aforementioned Rana chevronta, and Batrachuperus londongensis (EN), which is known only from the Longdon River.
Other protected areas include Luoji Shan Nature Reserve, which contains more than 2,000 species of higher plants, including more than 50 species of Rhododendron; and Gaoligong Shan Nature Reserve. Gaoligong Shan has recently been expanded across the Nu Jiang (Salween) and Lancang-Jiang (Mekong) rivers to link with the Bai Ma Xue Shan Nature Reserve and the east bank of the Jinsha River (part of the Yangtze) to create the Three Parallel Rivers World Heritage Site, which provides protection for the many different ridges and valleys and their highly distinctive flora. However, while a number of important areas are already protected in this hotspot, much more remains to be done, with the enormous watershed value of this region in and of itself providing more than adequate justification for increased protection (given that five of the great rivers of Asia originate on the 5,000-meter Tibetan Plateau).
One way of ensuring that the network of protected areas adequately conserves biodiversity is through the conservation and monitoring of Key Biodiversity Areas (KBAs), sites holding populations of globally threatened or geographically restricted species. KBAs are discrete biological units that contain species of global conservation concern and that can be potentially managed for conservation as a single unit. In the Mountains of Southwest China hotspot, Conservation International-China, in collaboration with Peking University and other local partners, is in the process of identifying and delineating KBAs. This work on KBA definition, supported by CEPF, is a refinement of the broad-scale priorities identified during the the 2002 Priority Setting Workshop, hosted by Conservation International (CI) and the World Wide Fund for Nature (WWF) and the Nature Conservancy (TNC). A proposed "EcoPartnership" composed of local biological research institutions, conservation NGOs, universities, and government agencies will aid in the refinement and monitoring of conservation outcomes by providing access to information through a data-sharing network.
A number of Chinese government policies represent hope for conservation in the Mountains of Southwest China. In response to the catastrophic floods of 1998, the government has completely banned logging within most of the hotspot. Other laws include a Land Conversion Program, also referred to as the Grain to Green Policy. This program includes a ban on agriculture on steep slopes, prohibitions against forest clearing for shifting agriculture, and specific species protection laws. The Land Conversion Program has provided important opportunities for biodiversity conservation. In this billion-dollar investment by the Chinese government, currently underway throughout the hotspot, farmers are given subsidies to replant barren slopes. Monocultures of pine and fruit trees have been an initial result, and conservation groups are hoping to work with the government to propagate more diverse native vegetation, and to expand biodiversity-friendly habitat throughout the region.
In addition its high biological diversity, the Mountains of Southwest China hotspot featuresa rich diversity of cultures. The hotspot is home to 16 ethnic groups, including Tibetans, who live in a large portion of the hotspot. In Tibetan culture, sacred landscapes have protected certain areas for centuries. Thousands of villages and monasteries have their own sacred site: a mountain, lake or patch of old-growth forest. However, this tradition has recently been challenged by outside influences and the demand for economic development. Preserving and reviving such a tradition will provide much impetus to protect the biodiversity in this hotspot.
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