Taiwan

Lucia Liu Severinghaus⁶² and Chang-Fu Hsieh⁶³

Biodiversity
Flagship Species
Threats
Conservation

Taiwan is situated at the western edge of the Asian continental shelf. It lies south of Japan via the Ryukyu Island chain, and is separated from the Asian mainland by a narrow strait (130 km at the narrowest point). The Tropic of Cancer cuts across the middle of Taiwan, and the warm Kuroshiwa Current passes along its eastern shore. As defined here, Taiwan includes 72 small islands, most of them with limited forest cover, except for Turtle Island (2.85 km²) and Lanyu Island (45 km²), which have substantial remaining tracts of natural forest, and has a total land area of 36 210 km². Although Taiwan, happily, has not lost so much of its natural habitat to meet the threshold for consideration as a hotspot, and also does not quite meet the hotspots threshold for plant endemism, detailed assessment of the island was necessary to demonstrate this. This chapter is, therefore, included here for the sake of documentation, and to make sure that this important island is incorporated into global conservation strategy.

Mountains and geographical location have combined to make Taiwan a beautiful place, giving rise to the well-known sixteenth-century Portuguese name, Ilha Formosa. More than two-thirds of Taiwan's surface is mountainous, with over 200 mountain peaks above 3 000 m in elevation, and the highest, Mt. Yushan or Jade Mountain, reaching 3 952 m. Taiwan is longer than it is wide, running 377 km north to south, and 142 km west to east. The eastern side of the island has steep slopes, narrow valleys, and small plains, while the western side has gentler slopes and broader plains.

Taiwan was formed around 4 million years ago, when a small piece of the Eurasian Plate was subducted under the Philippines Plate, resulting in the dramatic uplift of Luzon and Taiwan (Teng 1990). Indeed, the Taiwan Strait is only 60 m at its shallowest part at the current sea level (Yue-Gau Chen, pers. comm.), and when sea level was 60 m below its present level, it was connected with Fukien Province of mainland China. A landbridge has existed at four different stages over the course of the last 240 000 years (Chappell and Shackleton 1986), which has enabled faunal exchange to take place. However, the rising of the sea level at the end of the glacial periods rapidly reestablished the isolation of Taiwan from the mainland (Ferguson 1993).

The climate on the main island Taiwan is subtropical in the north and tropical in the south. Mean monthly temperature ranges from 34.1°C in July for Taipei to –5°C in January on the highest mountain. The distribution of rainfall on Taiwan is uneven; mean annual rainfall over the last 30 years has varied between 951 mm and 4 892 mm. In winter, northeastern winds bring persistent drizzle to northern and eastern Taiwan. Typhoons that come mostly in July to September usually cause abundant rainfall in eastern and southeastern Taiwan. Weather fronts that stall above Taiwan every May and June bring light rain interspersed with heavy downpours to northern Taiwan. Due to the topography, annual rainfall on Taiwan is higher in the north, the east, and in the mountains than on the southwestern plains. Because rivers on Taiwan are short and steep, the storage capacity of all watersheds is limited. Rivers typically swell up soon after heavy rain, but are then reduced to a narrow, shallow flow in a few days. Rainstorms and frequent earthquakes exert strong impact on the steep and unstable mountain slopes. Small-scale natural landslides are common. Typhoons often cause blow-downs, create gaps within forests, and influence the height of forests.

There are five life zones on the island: tropical rainforest in southern Taiwan and Lanyu, evergreen broadleaved forest, mixed forest, coniferous forest, and alpine grassland. The richest and least disturbed lowland evergreen broad-leaved forests are found in Hengchun Peninsula at the southern tip of Taiwan, and on Lanyu. Roughly 52.9% of the 820 species from Lanyu and 42.3% of the 912 species from Hengchun Peninsula have tropical affinities, while eastern Asian elements are relatively poorly represented. Hengchun Peninsula (280 km² in area) supports 49 endemic species, whereas 36 species are confined to Lanyu. In the global floristic system, these forests belong to the Philippinean Province of the Paleotropical Kingdom (Takhtajan 1986; Hsieh 2002), but are included here with the rest of Taiwan for geographic proximity and political convenience.

Less than 2% of the population on Taiwan can be considered indigenous people; the rest are Han Chinese who immigrated to Taiwan within the last four hundred years. Taiwan's indigenous people belong to 10 tribes, nine of which traditionally resided on Taiwan, while the Yami tribe lived on Lanyu. Each of these tribes has its own language and culture. The tribes on Taiwan have a hunting and slash-and-burn agricultural tradition, and their folklores contain rich stories of wildlife, hunting, and harvest. The Yami tradition is tied to fish, sheep, and yam and taro roots. All the indigenous people are now heavily influenced by Chinese culture, after several hundred years of contact, interracial marriages, and Chinese education. The lowland plain (Pingpu) tribes have been entirely assimilated into Chinese society. Excellent hunters with traditional knowledge of wildlife and nature were still common among Taiwan's tribes 30 years ago, but modernization and economic incentives have further diluted these traditional cultures. Only the Yami people still commonly practice their traditional knowledge of the sea, although there is a widespread movement for all the indigenous peoples to re-identify with their own traditions.

Biodiversity

Taiwan has high levels of endemism in both plants and animals. About 26% of vascular plants, 25% of mammals, 10% of resident birds, 25% of non-marine reptiles, and 33% of amphibians are endemic. In addition, a number of Taiwan's plants, amphibians, and freshwater fishes are relict species, meaning that Taiwan has served as a refugium for ancestors of these species during glacial periods. Upon the retreat of the ice sheets, the distribution of their relatives shifted north or up into the Himalayan Mountains, leaving them isolated on Taiwan. These populations survived in the mountains of Taiwan, and eventually diverged from their ancestors, becoming unique endemic species.

Taiwan has 4 101 species of native vascular plants belonging to 1 331 genera and 232 families. Around 1 071 species are known only from Taiwan, and for this reason it has been considered a Center of Plant Diversity (Davis et al. 1995). Two plant genera are endemic (Sinopanax and Kudoacanthus), and endemic species exist in 57.5% of the families. The ferns (at least 645 species) and orchids (337 species) are especially species-rich.

Plant diversity is higher in the more heavily impacted lowlands (below 500 m in elevation) than at upper elevations, although the proportion of endemism increases with elevation: 17.4% in the lowlands to 59.9% above 3 000 m. Evergreen broad-leaved forests between 500 and 1 500 m, which for the most part are subject to frequent human disturbance, contain at least 1 688 species of plants, including 419 species endemic to Taiwan. Between 1 500 and 2 500 m, there is mixed forest in which broad-leaved trees gradually give way to conifers. These forests boast an abundance of mosses, epiphytes, lichens, and tree climbers. Conspicuous emergent conifers tower above the largely evergreen broad-leaved canopy. Of the 1 324 species of vascular plants in these forests, 34.6% are endemic. Coniferous forests occur above 2 500 m and are relatively well protected, with more than 80% still pristine; of the 539 species of vascular plants occurring in these forests, 277 are endemic to Taiwan. The other species are the typical boreal-alpine species of Eurasia, distributed discontinuously in the Arctic north and the alpine zone in the south. Alpine grassland appears above 3 500 m. The dominant species in this habitat is the dwarf bamboo (Yushania niitakayamensis), which is often less than one meter tall on exposed areas. This species has a broad elevation range (ca. 1 400-3 600 m), but attains maximum development along high mountain ridges and slopes. This habitat is an important center of endemism, with 124 endemic plant species.

Currently, 79 species of mammals in 53 genera are known to occur in Taiwan (Liang-kung Lin, pers. comm.). Although no family or genus is endemic to Taiwan, around 20 species are, including seven bats and one carnivore, the Taiwan weasel (Mustela formosana). In addition, the Formosan macaque (Macaca cyclopis, VU) is endemic, although it has since been introduced to Japan, where it hybridizes with the Japanese macaque (M. fuscata). Most endemic mammals can be seen in more than one life zone, with the exception of five species of bats (two restricted to evergreen broad-leaved forest, two in mixed forest, and one in coniferous forest), one rodent, Coxing's white-bellied rat (Niviventer coxinga) in the mixed forest, and the Taiwan vole (Volemys kikuchii, VU) in the evergreen broad-leaved forest. The mixed forest contains the highest number of endemic mammals (14 species), whereas the coniferous forest and the evergreen broad-leaved forest each support nine endemics. The alpine grassland has six endemic mammals, while the only one found in the lowlands is the Formosan or Taiwan macaque, which is distributed widely on Taiwan.

Taiwan's native avifauna is characterized by 147 resident species, 15 summer breeders, and five suspected or occasional summer breeders. Fifteen species are endemic and, as such, BirdLife International has designated the island of Taiwan as an Endemic Bird Area (Stattersfield et al. 1998). Most species are found widely within their preferred altitudinal ranges, although above the tree line (3 500 m) only five species are found. The evergreen broad-leaved forests and mixed forests are of crucial importance to the maintenance of avian biodiversity in Taiwan, with the former supporting 58 species, and some 50 species of birds inhabiting the mixed forests between 1 500 and 2 500 m. Besides being exceptionally important for endemic birds, Taiwan lies on the main flyway for birds migrating between Japan and the Philippines, and is, therefore, of great importance for migrants from Japan, mainland China, and areas further north. Hence, in addition to the species already noted, there are 169 non-breeding migrants, 105 vagrants, and five species with unclear status, making a total of 446 species of birds that have been recorded from Taiwan.

Taiwan's reptile fauna includes 33 lizards, 45 snakes, and five turtles, of which 20 species (13 lizards and seven snakes) are endemic. Most snakes and lizards are found below 1 500 m, with only seven species of snakes and three species of lizards above 2 000 m. As regards amphibians, Taiwan is also home to 30 species of frogs and three salamander species, of which 13 frog species and all three salamander species are confined entirely to Taiwan. The family Ranidae is represented by 13 species, and four species are endemic; in contrast, seven out of 10 species in the family Rhacophoridae are endemic. More than 80% of the frogs and toads have an upper distributional limit of 1 500 m, and only four species reach 2 500 m; a single species of frog and three species of salamander are found at 3 000 m or higher. All the endemic species are at least locally abundant.

In terms of other animals, Taiwan's freshwater fish fauna is characterized by 227 species in 150 genera, of which 37 species are endemic. The landlocked salmon (Oncorhynchus masou) in central Taiwan is another relict species and has the southernmost distribution of the world's salmon species. Taiwan is also very rich in invertebrates. Butterflies are represented by 384 species, of which 12.5% are endemic (Yu-feng Hsu, pers. comm.), and there are 275 species of land snails on Taiwan, of which about 70% are endemic (Wen-lung Wu, pers. comm.).

Flagship Species

Taiwan's two endemic cypress species (Chamaecyparis spp.) are very important flagship species. The seven species of cypress that form ancient forest types now grow only on the west and east coasts of North America and in the mountainous regions of Japan and Taiwan. The two Taiwanese species found between 1 800 and 2 400 m are the only ones in the subtropical region. On the best sites, they can reach 50 m in height and more than 5 m in diameter, and live 3 000 years or more. Logging between 1900 and 1980 greatly reduced the virgin stands of these forests. Currently, about 48 500 ha of these forests remain. Taiwan cypress trees often form mixed stands with other conifers and broadleaved species.

Another important plant flagship is Taiwania (Taiwania cryptomerioides, VU), like Metasequoia and Sequoiadendron, one of the world's classic Tertiary relict gymnosperms. Recently, what is probably the world's largest population of Taiwania was discovered in southern Taiwan (Yang and Wang 2002). In an area of about 1 300 ha, at least 10 000 mature trees stand shoulder to shoulder, some of them measuring 60 to 70 m in height, with trunks more than four meters in diameter. The Taiwan beech (Fagus hayatae, VU) has a relict distribution in northern Taiwan and forms one of the rare deciduous forests in Taiwan. It is found in a nearly pure stand of at least 1 300 ha, located between 1 300 and 2 000 m along the northern ridge of Hsuehshan Range, with evergreen oak forest below and mixed coniferous forest above. Strong northeasterly winds in winter stunt these trees to less than five meters on the summit, although they grow to over 10 m on the adjacent leeward slopes.

The clouded leopard (Neofelis nebulosa, VU) used to be found in eastern and southern Taiwan in forests above 1 000 m, but the last confirmed sighting of this species was in 1983. Given its extremely secretive habits and the rugged topography of Taiwan, conservationists had hoped that some individuals might survive in deep forests. Unfortunately, recent intensive efforts aided by automatic infrared photography turned up no sign of this species and it probably no longer occurs on Taiwan. The Asiatic black bear (Ursus thibetanus, VU) is the largest mammal on Taiwan. It lives in the mountains between 1 500 and 3 500 m, foraging mostly on plant matter mixed with wasp nests and animal carcasses. The current population is estimated to be between 200 and 1 000 individuals.

The two endemic pheasants are also obvious flagship species. The Mikado pheasant (Syrmaticus mikado) was first discovered when two male tail feathers were found on an aboriginal headdress. These feathers were so unique as to form the basis of a description of a new species named in 1906. The plumage of the Mikado pheasant is elegant and understated, whereas Swinhoe's pheasant (Lophura swinhoii) is flashy in its color pattern. The Mikado pheasant lives in forests above 2 000 m on steep slopes, while Swinhoe's pheasant occurs in lowland forests up to 2 200 m on gentler slopes. They are both secretive, producing almost no vocalization, and are extremely wary of people. They only come into the open at dawn or dusk or when it is foggy or raining. Once the sun is out, they withdraw into the shade of deep forests.

The Taiwan flamecrest (Regulus goodfellowi) is another endemic bird that was characterized by W.R. Ogilvie-Grant in 1907 as being more colorful than others in its genus. In fact, this flamecrest is a relict species once classified as a subspecies of the European flamecrest (R. ignicapillus). Given that the genus has not yet been recorded between Asia Minor and Taiwan, it has been cited as an excellent example of disjunct species distribution in birds (Hachisuka and Udagawa 1951).

A few migratory bird species are also important flagships. Indeed, one such species, the black-faced spoonbill (Platalea minor, EN), is the best-known bird in Taiwan. The species is found only in eastern Asia, and totals a little more than 1 000 individuals. Two-thirds of the world population of this species winter in one concentrated flock at the Tsengwen Estuary in southern Taiwan. Since 1995, international and local conservation efforts have put this species in newspaper headlines numerous times. Hundreds of tourists go to watch them rest or bathe in shallow water each day during the time they are present on Taiwan. A conservation action plan was formulated for the black-faced spoonbill in 1995, to be updated in 2003 (Severinghaus et al. 1995).

The grey-faced buzzard eagle (Butastur indicus) is another important migratory species. This bird breeds in the temperate region and goes south to winter. The southern tip of Taiwan is a point of concentration for migratory raptors, and the peak of this species' southward migration often falls around October 10; consequently, the grey-faced buzzard eagle has been nicknamed the National Day bird. Each year during the National Day holiday, huge crowds arrive to observe the National Day bird as it gathers in flocks of thousands. Every time a flock is seen coming to roost at dusk or departing at dawn, it draws excitement from the enthusiastic crowd. Many people become bird watchers subsequent to such an experience.

Among the invertebrates, a beautiful birdwing butterfly (Troides magellanus) is an important flagship. Found only on Lanyu, it has been reduced by overtrapping for the butterfly trade. Its larvae feed on only one species of plant (Aristolochia kankaoensis), and grazing by cattle and other human activities have reduced the abundance of this key food plant. Now with cattle mostly removed from Lanyu, planting of A. kankaoensis seedlings and releasing captive-raised butterflies into the wild appear to have increased the butterfly population, but future monitoring is needed before success can be claimed.

Threats

Habitat loss is the greatest threat to biodiversity on Taiwan. Being a small island with a high population density (622 persons per km² in 2002; Population Reference Bureau 2003), Taiwan is under intense development pressure. Most of the natural habitat below 500 m has been converted to human use, and increasing development pressure and economic aspirations have already begun to alter habitat at higher elevations. Improper land-use practices have led to habitat loss upstream and habitat degradation downstream, and have accelerated water and soil erosion. Channelization of rivers or the construction of check dams as measures to control flooding has destroyed riparian habitat, and often substituted natural river conditions with cemented river banks or even stream beds which are foreign and hostile environments for aquatic organisms. Nevertheless, even under high population and development pressure, 59% of Taiwan is still forested, and 73% of the forests are natural forests (more than 35% are mature forests), suggesting that some 43% of Taiwan's original forests remain intact. However, much of the remaining intact vegetation is at higher altitudes and, in fact, less than 1% of the original lowland vegetation is estimated to remain on Taiwan (Editorial Committee of the Flora of Taiwan 1993–2002).

There was a long history of traditional hunting, trapping, logging, and collecting of forest products on Taiwan, but the government began regulating the harvesting of wildlife in the late 1970s. Although illegal hunting still occurs, public education efforts have reduced the general demand for wildlife. Logging of primary forest and other ecologically important forests was stopped in 1991. However, certain plants continue to be harvested without sufficient control, especially those that are rare, have showy flowers or foliage, or have supposed medicinal qualities.

Invasive species are an issue in Taiwan, with several having entered through the pet trade, for agricultural purposes, for private collections or by accident. Not enough data exists about Taiwan's natural conditions prior to the arrival of most of these species, or about their point of entry and subsequent expansion, and in most cases they were not noticed until ecological or commercial damage was already serious. Examples include the freshwater apple snail (Pomacea canaliculata), armored catfish (Hypostomus spp.), bullfrog (Rana catesbeiana), red-eared slider turtle (Trachemys scripta), a crawling plant (Mikania micrantha), and water hyacinth (Eichhornia crassipes). Among the few well-documented examples of the impact of an invasive are hybridizations between the endemic Taiwan bulbul (Pycnonotus taivanus, VU) and the Chinese bulbuls (P. sinensis) or between the Taiwan hwamei (Garrulax canorus taewanus) and the Chinese hwamei (G. c. canorus), both of which are reducing the genetic distinctiveness of the Taiwan endemics such that genetically pure populations remain in only a few isolated parts of their former range (Severinghaus and Chi 1999; BirdLife International 2003; Liu 2003).

Conservation

Many laws provide the legal basis for nature and biodiversity protection in Taiwan. The Cultural Property Protection Act covers natural heritage such as important endemic species or special landscapes (1982). The National Park Law (1983), the Wildlife Conservation Act (1989), the Forestry Law (1985), and other laws together regulate land use, human behavior, and the use of biodiversity. In 1994, Taiwan passed the Environmental Impact Assessment Act, which requires major development projects to carry out environmental impact evaluations before development permits are granted.

About 15% of Taiwan has some level of protection, a figure that drops just slightly when one considers only protected areas classed in IUCN categories I to IV. Taiwan's protected areas include five national parks, 15 nature preserves, 19 wildlife refuges, 29 important wildlife habitats, and nine national forest protected areas. These areas are set aside to protect relatively large tracts of natural habitat and the wildlife within them or to preserve special landscapes. Nevertheless, an increased level of protection is required for the lower-altitude forests.

Nature education programs are numerous in the cities. These are either sponsored by government agencies, schools or other institutions, or organized by environmental NGOs with funding from government agencies or the private sector. Researchers are often invited to give public lectures to introduce their new findings. Media exposure helps to draw public attention to charismatic species or special habitats such as mangroves with viviparous plants (Kandelia obovata). The story of the landlocked salmon has been included in high school textbooks. Satellite tracking of the green sea turtle (Chelonia mydas, EN), which comes on shore to lay eggs, has greatly increased its prominence with the general public. News of the recovery of migratory Taiwan butterflies (Parantica sita niphonica) in Japan catapulted the already popular sport of butterfly watching into organized public monitoring activities. With the exception of the highly popular bird-watching and butterfly-watching activities, most existing education programs focus on flagship species. Future education needs to increase people's understanding of ecological functioning and the significance of all species, including the large number of non-charismatic ones.

Biodiversity inventories have been established by government agencies and academic institutions. The usefulness and quality of these inventories can only be strengthened with continued monitoring of species distribution, population sizes, and ecological interactions, as well as an increased understanding of their genetic diversity. The critical nature of this task is reflected by the fact that a large proportion of Taiwan's terrestrial vertebrates have never been studied and their natural history remains largely unknown. Government agencies have implemented various conservation actions, including artificial propagation of the landlocked salmon and the birdwing butterfly. After 20 years, salmon restoration work remains far from complete. Inappropriate land use along streams has proven very difficult to change. More research is needed to identify the exact water and river conditions required by the species.

Many communities have organized and implemented biodiversity conservation programs for their own areas, including issuing community-based fishing permits to earn income, patrolling streams to prevent overfishing, and establishing fishing bans to allow stocks to recover. These programs have proven highly successful for a number of streams. However, although the benefits of such actions are enormous, the question of whether or not privatization of biodiversity resources is consistent with social justice, and to what extent natural resources (e.g., water in the river) should be privatized, requires further analysis.

Finally, given that a large amount of habitat on Taiwan was damaged in the past, it is now important to look into restoration, to carry out research to bring back critical areas, and to develop plans to return degraded areas to ecologically healthy conditions.

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