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Biodiversity

The endemic flightless kiwi is a national icon.

New Zealand's geographic isolation for 80 million years[151] and island biogeography is responsible for the country's unique species of animals, fungi and plants. They have either evolved from Gondwanan wildlife or the few organisms that have managed to reach the shores flying, swimming or being carried across the sea.About 82 percent of New Zealand's indigenous vascular plants are endemic, covering 1,944 species across 65 genera and includes a single family.The number of fungi recorded from New Zealand, including lichen-forming species, is not known, nor is the proportion of those fungi which are endemic, but one estimate suggests there are approximately 2300 species of lichen-forming fungi in New Zealand[153] and 40 percent of these are endemic.[155] The two main types of forest are those dominated by broadleaf trees with emergent podocarps, or by southern beech in cooler climates. The remaining vegetation types consist of grasslands, the majority of which are tussock.

Before the arrival of humans an estimated 80 percent of the land was covered in forest, with only high alpine, wet, infertile and volcanic areas without trees.[158] Massive deforestation occurred after humans arrived, with around half the forest cover lost to fire after Polynesian settlement.[159] Much of the remaining forest fell after European settlement, being logged or cleared to make room for pastoral farming, leaving forest occupying only 23 percent of the land.[160]

The forests were dominated by birds, and the lack of mammalian predators led to some like the kiwi, kakapo and takahē evolving flightlessness.[161] The arrival of humans, associated changes to habitat, and the introduction of rats, ferrets and other mammals led to the extinction of many bird species, including large birds like the moa and Haast's eagle.[162][163]

Other indigenous animals are represented by reptiles (tuataras, skinks and geckos),[164] frogs, spiders (katipo), insects (weta

) and snails.[165][166] Some, such as the wrens and tuatara, are so unique that they have been called living fossils. Three species of bats (one since extinct) were the only sign of native land mammals in New Zealand until the 2006 discovery of bones from a unique, mouse-sized land mammal at least 16 million years old.[167][168] Marine mammals however are abundant, with almost half the world's cetaceans (whales, dolphins, and porpoises) and large numbers of fur seals reported in New Zealand waters.[169] Many seabirds breed in New Zealand, a third of them unique to the country.[170] More penguin species are found in New Zealand than in any other country.[171]

Since human arrival almost half of the country's vertebrate species have become extinct, including at least fifty one birds, three frogs, three lizards, one freshwater fish, and one bat, and four plant species have become extinct.[162]. Others are endangered or have had their range severely reduced.[162] The number of fungi which have become extinct, endangered or reduced in range is not known. However New Zealand conservationists have pioneered several methods to help threatened wildlife recover, including island sanctuaries, pest control, wildlife translocation, fostering, and ecological restoration of islands and other selected areas.[172][173][174][175] According to the 2012 Environmental Performance Index, New Zealand is considered a "strong performer" in environmental protection, ranking 14th out of 132 assessed countries.[176]



 


Date: 2015-01-29; view: 520


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