|MadSci Network: Environment & Ecology|
I assume that by 'colonization,' you mean European colonization. There have actually been two "colonizations" of Australia. The first was approximately 35,000 - 40,000 years ago, when the aborigines arrived on the continent. They brought dingoes with them, a new predator that is thought to have had a devastating effect on wildlife there. The second was around 1800, when Europeans arrived in Australia, bringing dogs, guns, rats, cows, goats, agriculture, rabbits, and foxes, among other things. Extinctions from the first colonization are difficult to determine, because fossil records are always spotty at best. There is a lot of debate over whether extinctions in the last 30,000 years were caused by man (overhunting) or by other factors, such as climate. About 50 animal species are thought to have gone extinct between the first and second colonizations. Most of those are mammals, with a few reptiles and bird species, including the large flightless moa. In that same time, North America was colonized by humans, and some three dozen large animal species went extinct--again, there is a lot of debate over whether humans were the sole cause, only a partial cause, or not involved at all. By contrast, most of the extinctions since European colonization can be traced more or less directly to the hand of man. In Australia, about 22 mammal species, but no bird species, have gone extinct since Europeans arrived there. It is interesting to note that although Australia is often held up as an example of how man can drive creatures extinct, the same number of mammal species (22) have gone extinct in North America since colonization in about 1600, plus eight bird species. The most alarming part of this is to compare the rates of extinction: in Australia, about 50 species over 30,000 years--and then nearly half that number in the last 200 years. Note, too, that none of these figures include extinction of insect species, which we have no reliable way of tracking, because fossil records and historical records are so poor for them. (A valuable source of information for this answer was Jared Diamond's article: "Historical Extinctions: A Rosetta Stone for Understanding Prehistoric Extinctions" in Quaternary Extinctions, Paul Martin and Richard Klein, eds., 1984, along with other articles in that publication.)
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