Biological diversity in the Chilean winter rainfall-valdivian forests
A virtual continental island bounded by the Pacific Ocean on the west, the Andes Mountains on the east, and the Atacama Desert in the north, the Chilean Winter Rainfall-Valdivian Forests Hotspot harbors richly endemic flora and fauna. The hotspot covers 397,142 km2 of the central-northern part of the nation of Chile and the far western edge of Argentina, stretching from the Pacific coast to the crest of the Andean mountains. The hotspot encompasses about 40 percent of Chile’s land area and includes the offshore islands of San Félix and San Ambrosio and the Juan Fernández Islands.
The area of central-northern Chile is characterized by a winter-rainfall regime, while the northern part of southern Chile is characterized by rainfall all year round. The winter-rainfall area is divided almost equally between a typical Mediterranean-type climate area (155,000 km2) and a more arid area of winter-rainfall deserts (145,000 km2).
Vegetation types in the more northerly winter rainfall desert area include an extended band of coastal fog (camanchaca) desert and the more southerly inland desierto florido. Other vegetation types include coastal and inland matorral and savannas, deciduous forests and high-elevation alpine vegetation. On the lower western slopes of the Andes and the eastern slopes of the Coast Range, the typical matorral is open and contains a rich assemblage of endemic herbaceous and geophyte species. In the wetter climate of the western side of the Coast Range, the forests are closed. At higher elevations, the typical Mediterranean sclerophyllous vegetation grades up to Nothofagus forest. In addition, there is a small tongue of coastal rainforest along the southern coast from 39º S southwards.
The Chilean Winter Rainfall-Valdivian Forests Hotspot represents the crossroads of two major floristic and faunistic regions: the Neotropical and ancient Gondwanan provinces. The influence of past geographical links between South America and other southern lands, such as Australia, is evident in the hotspot’s high plant endemism.
Of the nearly 4,000 vascular plants found in this hotspot, about half are endemic. These numbers represent about three-quarters of all Chilean plant species and endemics in only 40 percent of the land area. Plant diversity in the winter-rainfall area is around 3,539 species (compared with the Valdivian Forests which support only around 1,284 species), of which 1,769 (50 percent) are endemic to that subunit. The Juan Fernández Islands have a flora comprised of 200 native species, as well as over 200 introduced species, many of which are natives of continental Chile. The isolation of these offshore islands causes high endemism in their native floras, with 62 percent endemism.
The hotspot is home to three endemic plant families (Aextoxicaceae, Gomortegaceae and Lactoridaceae), and several monotypic endemic plant genera (Pitavia, Legrandia, and Jubaea). The ruil forest of coastal central Chile is an important refuge for the endemic trees Gomortega keule and Nothofagus alessandri. At present, it remains as a narrow strip only 100 kilometers long and is disappearing at the rate of eight percent each year as native forests are cleared for Monterey pine (Pinus radiata) plantations.
Although not rich in species, the plant communities of the Valdivian Forests also include primitive Asteraceae species and representatives of the Andean family Calyceraceae, both thought to be remnants of ancient plant communities from the supercontinent Gondwanaland. They provide valuable windows into the evolutionary history of plants.
Among other notable plant species in the hotspot are the araucaria trees (Araucaria araucana) and Chile's national flower, the copihue or Chile-bells (Lapageria rosea).
Characteristically, birds are not very well represented in this hotspot. The region's bird diversity includes just over 225 species. There are a dozen endemic bird species here, including three breeding species of petrel, and the region is considered a priority Endemic Bird Area by Birdlife International. The hotspot also has two monotypic endemic bird genera: Sephanoides, which is represented by the Juan Fernández firecrown (S. fernandensis, CR), confined to the Juan Fernández Islands, and the green-backed firecrown (S. sephaniodes), and Sylviorthorhynchus, which is represented by the Des Murs’ wiretail (S. desmursii), restricted to the temperate forest in south-central Chile.
Mammal endemism is relatively low, with almost 70 species and only 15 endemics. There are, however, five endemic genera. The rodent genus Octodon comprises three species of degus, while the remaining four genera are all represented by single species: the Chilean climbing mouse (Irenomys tarsalis), the Chilean shrew opossum (Rhyncholestes raphanurus), the coruro (Spalacopus cyanus), and the monito del monte (Dromiciops gliroides, VU). The last-named species is not just the only genus in an endemic family, the Microbiotheriidae, but the only known representative of an entire order, the Microbiotheria (this is the only hotspot to host an endemic mammalian order). The species is known only in the proximity of Concepción south to Chiloé Island, south-central Chile, and in the mountains east of the Argentine border.
One well-known endemic rodent species is the chinchilla (Chinchilla lanigera, VU), prized around the world for its soft, dense fur. Chinchillas have been hunted and trapped nearly to extinction in the wild, although they are widely bred in captivity. Darwin’s fox (Pseudalopex fulvipes, CR) exists in only two known populations, one in the forests of Chiloé Island and another in the coastal mountains of Naheulbuta National Park.
Other notable mammals include the mountain vizcacha (Lagidium viscacia), a large, gregarious rodent that lives high in the upper reaches of the Andes; the pudu (Pudu puda, VU), the smallest South American deer, which lives at lower elevations and is declining rapidly as a result of habitat destruction, competition with livestock, and hunting; the Andean cat (Leopardus jacobita, EN); and two species of brown bats, the Atacama myotis (Myotis atacamensis, VU) and Chilean myotis (M. chiloensis), both restricted to this region. The endemic Juan Fernández fur seal (Arctocephalus philippii, VU) breeds on the Juan Fernández islands.
Endemism levels for both reptiles and amphibians are high. About two-thirds of the hotspot’s more than 40 reptile species are endemic. A large number of these species are lizards, found at mid-to-high elevations. The lizard genus Liolaemus accounts for three-quarters of the reptile species in the hotspot and, of these, two-thirds are endemic. Interestingly, there are only two representatives of the world's largest snake family, Colubridae, namely Chilean green racer (Philodryas chamissonis), which is endemic, and Chilean slender snake (Tachymenis chilensis); there are no terrestrial or freshwater turtles found here.
Around three-quarters of the more than 40 amphibian species in the hotspot are endemic. Additionally, one family (Rhinodermatidae) and five genera are endemic to the hotspot: Telmatobufo, with three species, all threatened; Rhinoderma, with two species; and Insuetophrynus, Caudiverbera, and Hylorina, each with a single species. Furthermore, this is one of the few hotspots with an endemic amphibian family (Rhinodermatidae), with Darwin’s frog (Rhinoderma darwini, VU) and the Chile Darwin’s frog (R. rufum, CR) among the most important flagship species for this region.
Although the hotspot has a relatively small fish fauna, with only just over 40 native species, it has a remarkable two endemic families: the mountain catfishes (Nematogenyidae) and the perch-like fishes of the genus Percilia (family Perciliidae). Nearly 20 percent of the region’s fish species are relicts of Gondwanan groups and are also found in southern Africa, Australia, and New Zealand.
The ecosystems of the Chilean Winter Rainfall-Valdivian Forests face severe pressure from human activities and development. Chile has one of the fastest growing economies in Latin America and is still strongly dependent on natural resources. Most of the major threats are concentrated in the Mediterranean subunit in the southern part of the hotspot, where a high percentage of the Chilean population lives today.
Habitat degradation and forest clearing began in the 16th century with the arrival of Spanish colonists. In subsequent years, huge areas of deciduous and evergreen forests were burned in the south. Forest cutting for timber and fuel wood continued well into the 20th century. Since the 1970s, the establishment of large-scale pine and eucalyptus plantations has spurred the clearing of 20,000 km2 of native vegetation in the southern portion of the hotspot including the diverse forests of the Coast Range. These man-made forests are valuable for soil stabilization and halting erosion, but they fragment remaining stands of native vegetation. This splintering slows gene flow among plant species and acts as a barrier to many habitat-specialist animals.
Other major threats to the integrity of Chilean ecosystems include accidental and intentional forest fires. Unlike the other Mediterranean-type climate zones, fires are not a major natural part of the ecosystem in the Chilean Winter Rainfall-Valdivian Forests, and plant and animal species are not adapted to its effects. Between the 1970s and 1990s, an estimated 360-600 km2 were burned each year in this region. The Monterey pine (Pinus radiata) is a non-native, fire-adapted species that is often planted on Chilean tree plantations; fires here can easily spread to vulnerable native forests.
Overgrazing by domestic animals has also contributed to the heavy degradation of matorral vegetation below the treeline. Grazing by goats and European rabbits, introduced in the early 1900s, threatens native vegetation in the drier parts of the north. Throughout the hotspot, invasion by introduced weedy species and perennial shrubs, assisted by forest fires and overgrazing, is crowding out native vegetation. The illegal trade and export of native species, particularly reptiles, is also a problem in some cases. As is the situation in nearly all of the world's hotspots, other threats include various forms of urbanization. Two examples from the Chilean Winter Rainfall-Valdivian Forests region are the development of coastal areas for tourism and the construction of highways and hydroelectric complexes.
In total, about 30 percent of the hotspot's original vegetation remains in pristine condition, much of it in the winter-rainfall deserts subunit.
Around 50,000 km2, or 12.8 percent, of the original land area of the Chilean Winter Rainfall-Valdivian Forests is under official protection, and fortunately most of it is in protected areas in The World Conservation Union (IUCN) categories I to IV. Protected areas include national parks, national reserves, national monuments, and nature sanctuaries. All Araucaria trees are also protected as national monuments, an unusual and creative conservation mechanism. The total area under protection, much of it in many small reserves, however, is inadequate to conserve biodiversity in the long run. Particularly in the northern part of the rainforest zone, protected areas tend to be at mid-elevations and concentrated in the Andean Cordillera, leaving the richest rainforest areas along the coast practically unprotected.
While a limited level of scientific knowledge about existing species hampers effective conservation in the Chilean Winter Rainfall-Valdivian Forests, the biggest long-term conservation challenge is the land tenure situation. Practically all land not currently included in government-protected areas is privately owned, and there is no public land available for new protected areas. Purchasing private land for protection by the government is complicated and expensive. There is a provision in Chilean Environmental Law allowing for private reserves, and Pumalin Park, a well-known private conservation initiative, is located in the rainforest zone of this hotspot.
Effective long-term biodiversity conservation in Central Chile will depend on cooperation between the government, the private sector, and individual citizens. In November 2003, an important conservation step was taken when The Nature Conservancy, in partnership with the Conservation International Global Conservation Fund, the World Wildlife Fund and local conservation organizations, acquired 60,000 hectares (600 km2) of biologically-rich temperate rainforest in an open auction. Part of this land will be cooperatively managed with three adjacent national reserves and hopefully will eventually be elevated to national park status. The rest of the land will be owned and managed by a new Chilean conservation organization.
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