An essay on Australia's unique flora and fauna

Essay by BYLuoHigh School, 10th gradeA, July 2008

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The long geographic isolation of Australia fromother continents has resulted in an exceptionalvariety of plant and animal life. From arid centralAustralia to the tropical forests of northQueensland, no other country has such a variety.

More than 80 per cent of Australia's flora andfauna is found nowhere else in the world. Theestimated number of native and introducedspecies living in Australia Ð about one millionÐ is more than twice the number of species inNorth America and Europe combined.

Due to the generally low amounts of rainfall andits unreliability, most of the flora in Australia ischaracterised by drought-resistant qualities. TheAustralian land flora comprise over 12 000 speciesand many of these are endemic to Australia Ðthat is, they occur naturally in Australia andnowhere else in the world. For example, most ofAustralia's 500 different species of Eucalyptus(gum trees) are endemic. Some plant species arenot only unique to Australia but also unique tosmall areas of Australia. For example, about 75per cent of the flowering trees and shrubs in thesouth-west corner of Australia have been found tobe unique to this area.

Grass trees (Xanthorrhea sp.) are among the many plantspecies that are endemic Ð they occur naturally only inAustralia.

UNIQUE FLORAThe distribution of vegetation in Australia isstrongly influenced by climate. Only about five percent of Australia is forested. Most of this forest vegetationoccurs along the wetter eastern coast andhighlands area. The forests are dominated by eucalypttrees, which are tough and durable and able towithstand the frequent ongoing winds that occur. As rainfalldecreases inland, trees decrease in number andbecome smaller and further apart. Eucalypts arestill the main types of tree found there. Furtherinland, as the climate becomes increasingly dry,grasslands and shrubs begin to dominate.

Most of the world's marsupials are found inAustralia. They include the bandicoot, koala,kangaroo, wallaby, wombat and the Tasmaniandevil. Marsupials have pouches in which theysuckle and carry their young. Marsupial babiesare born in a tiny immature state and completemuch of their development in the pouch.

Despite the number of unique marsupials inAustralia, most of our native animals are not marsupials.

Most are placentals, which means that theyoung remain in the womb for much longer thanmarsupials and there is no pouch. Australian placentalanimals include bats and rodents and suchmarine mammals as seals, dugongs and dolphins.

Most mammals reproduce by giving birth to liveyoung. Monotremes are unique in being the onlymammals that lay eggs. There are only threespecies of monotreme in the world: the platypusand two species of echidna. One echidna speciesoccurs in New Guinea but the platypus and theother species of echidna are uniquely Australian.

Loss of species in Australia has been largelycaused by habitat destruction and degradationand this problem is still occurring. Because mostAustralian species are found nowhere else, wehave a special responsibility to conserve them.

There are the same number of species ofreptiles in an average Australian backyardas there are in the whole of England.