Zebra mussels contributed to the improvement of Lake Erie's water clarity. Research shows that in the early ‘70s, water clarity was approximately 3 feet. It improved to 6 to 10 feet in the 1980s after a decade of reduced phosphorus inputs, and improved again to 10 to 17 feet in the early 1990s, after zebra mussels colonized the area.
The most destructive and most expensive transfer ever of an animal from one country to another was that of the European rabbit (similar to a cottontail) into Australia. It was introduced by a wealthy landowner, Thomas Austin, who had become homesick for the animals of his native England. Rabbits were not native to England either; they were introduced from Europe after the Norman conquest in 1066. Mr. Austin brought in a shipment of two dozen rabbits in 1859, and turned them loose on his estate in Victoria. They bred like rabbits, and provided some good hunting for Mr. Austin. Six years later he estimated that he had killed 20,000 rabbits and still had 10,000 left. They spread out across the continent, rabbit hunting became popular, and rabbit meat and fur became a major export for Australia. They did so well because their populations were not kept in check by weasels and foxes as they are in Europe. The only possible predators - the dingo and the Tasmanian wolf - were already being shot and kept in check by the sheep ranchers. And many of the rabbits' potential competitors, like kangaroos, were also being exterminated by the settlers.
In 50 years rabbits had spread all over Australia except the tropical regions in the north, and their populations were so dense that they would eat every blade of grass, and kill shrubs and trees by stripping them of their bark. They were denuding the sheep pastures of grass, turning once successful ranches into wastelands and reducing wool production by half. Finally they were declared vermin and were hunted, trapped, and poisoned. The government offered a bounty for rabbit tails, and millions were collected. But it is very difficult to catch every one. In 1902-1907 they built a 2,000-mile long fence, costing more than a million dollars, to try to stop the rabbits entering the cereal-growing area in the southwest. Rabbits starved to death and carpeted the ground with their bodies on one side of the fence, while the grass grew green on the other, for a while. Then a few rabbits got through and started the whole cycle again on the other side of the fence.
Today the "Rabbit Fence" marks a clear and straight boundary between the southwest, where all native vegetation was cleared to make way for agriculture, and the area to the east where forest still survives. This man-made alteration in the vegetation pattern is the most conspicuous man-made feature of Australia when viewed from space, and it appears to be causing a change in rainfall patterns.
I dunno, this whole topic seems kinda made up to me. Isn't this just evolution in progress? I don't see what difference it makes how a species moves from one place to another really, isn't it all part of the process?
« Older What will you wear... | Iran gets bombed June 2005.... Newer »
This thread has been archived and is closed to new comments
Buy a Shirt