Taiwan's Geography and climate

Taiwan's Geography

The main island of Taiwan, measures nearly 400 km from north to south and around 145 km from east to west at its widest, and constitutes 99 percent of the total area under the nation's jurisdiction.

As the island lies along a seismic belt, tectonic movement dictates some of its most prominent geological characteristics. A tilted fault block runs down the center of the island to form the central mountain ranges and, to the east of the island, a narrow longitudinal fault valley stands between this fault block and the Pacific Ocean. The slopes of the block's western flank descend gradually, giving way to fertile coastal plains where the majority of people, agriculture, and industry is concentrated. The island's shoreline is relatively unbroken, with small areas of coral reef around its southernmost tip.

Taiwan proper can be divided into five major physiographical divisions: mountain ranges, volcanic mountains, foothills, tablelands, and coastal plains and basins. Taiwan's five longitudinal mountain ranges, which are mostly forested, occupy almost half the island, with more than two hundred peaks over 3,000 meters. Steep mountains over 1,000 meters high constitute about 31 percent of the island's total land area, making for some of the island's most dramatic and beautiful scenery. As a group, the mountain ranges extend 330 km from north to south, almost the entire length of the island, and an average of about 80 km from east to west. The highest peak is Jade Mountain at 3,952 meters tall, which is also the highest mountain in East Asia. See 'Taiwan's Mountain ranges', Taiwan's top 100 mountains' and Taiwan's National Parks'

Flora and Fauna

Taiwan's tropical-to-temperate spectrum of climatic zones and contrasting topographies has endowed the island with a rich diversity of flora and fauna. Some 70 species of mammals, 500 species of birds (40 percent of which reside on the island all year round), 90 species of reptiles, 30 species of amphibians, 2,700 species of fish, and 18,000 identified species of insects (including some 400 butterfly species) are known to inhabit Taiwan. The abundant plant life in Taiwan includes 610 species of ferns, 28 species of gymnosperms, and 3,600 species of angiosperms. Around 27 percent of vascular plant species and 11 percent of animal species found on the island are endemic to Taiwan.

Perhaps the most famous Taiwanese species of fauna is the Formosan landlocked salmon. It is believed to have become trapped in the frigid mountain waters of central Taiwan during the last Ice Age when ocean levels dropped dramatically and the salmon could no longer migrate back and forth from fresh water to salt water. Overfishing and pollution have damaged much of the salmon's natural habitat, causing the distribution and population to shrink dramatically. In 1989, the Council of Agriculture listed the Formosan landlocked salmon as an endangered species in accordance with the Wildlife Conservation Act, and in 1997 the Taichung County government established the Formosan Landlocked Salmon Refuge in the upper reaches of the Dajia River in Shei-pa National Park.

Climate

Though a wide range of climatic zones can be found across Taiwan, the area generally enjoys an oceanic and subtropical monsoon climate. Summers are long with high humidity; winters are short and usually mild, though snow is possible on the peaks of high mountains during the coldest months. Frost is rare in the lowlands where most of the population is concentrated. Mean monthly temperatures range from 15°C to 20°C in the winter to around 28°C in the summer. Taiwan's surface temperature has increased about 1.4°C in the past 100 years, about twice the global mean (0.6°C).

Taiwan's annual weather patterns are greatly influenced by the East Asian monsoonal flow. The winter monsoon lasts from October to late March and brings steady rain to northeast Taiwan, while the central and southern parts of the island are left with mostly sunny winters. Many of Taiwan's offshore islands experience especially strong winds during the winter monsoon. The onset of the summer monsoon season is signaled by "plum rain" in May and June and usually ends in late September. High levels of precipitation fall in the south while the north is relatively dry.

As Taiwan lies close to the earth's most active tropical cyclone formation zone in the West Pacific, summer months are also marked by frequent thunderstorms and typhoons, with an average of three to four typhoons hitting Taiwan each year. Though strong winds and heavy rainfall can often cause severe damage, the storms are also a significant source of water, with windward mountain slopes sometimes receiving as much as 300 mm of rainfall in 24 hours.

Mean annual rainfall in Taiwan is approximately 2,500 mm. The southern area of Taiwan receives 90 percent of its rainfall between May and October; precipitation falls more evenly in the north, with 60 percent falling between May and October. Despite Taiwan's abundant rainfall, water resources can be scarce as the nation's rivers tend to be steep and flow rapidly. Throughout the country, the driest period is between November and February.

Earthquakes

Taiwan experiences relatively frequent seismic activity due to its location on the circum-Pacific seismic belt and at the junction of the Manila and Ryukyu trenches along the west side of the Philippine Sea plate (PSP). However, most tectonic movement in Taiwan is weak and has no impact on people's lives. In fact, more than 95 percent of earthquakes cannot be detected without a seismometer.

The PSP and Eurasia plate (EUP) converge at a rate of about seven to eight centimeters per year. The convergence, which created the uplift that formed Taiwan's four central mountain ranges, continues its movement, putting most of the Taiwan area under a northwest-southeast compression. East of Taiwan, the PSP subducts northward beneath the EUP, while to the south of the island, the EUP underthrusts eastward beneath the PSP. Seismic activity in northeast and south Taiwan is associated with the two subduction zones. Activity in the rest of Taiwan is complex and less predictable. Geologists have identified 42 active faults on the island.

In central and west Taiwan, earthquakes are less frequent, of a smaller scale, and have a shallow focus. However, on September 21, 1999, a major earthquake occurred near Jiji Township in Nantou County, central Taiwan, registering 7.3 on the Richter scale. It was the largest seismic event to affect Taiwan in all of the 20th century.