Environmental Engineering Reference
In-Depth Information
nature, an animal which seems to have taken the wrong turning, bent on total
destruction.
—Daphne Sheldrick, The Tsavo Story , 1973
There are many examples of this human hubris and its failures in the
environmental realm, as well as in other spheres of human concern.
Among them is a particularly visible and striking example from Mac-
quarie Island, a 50-mile spot of land in the Southern Ocean about
halfway between Australia and Antarctica. 11 The island was discovered
in 1810 and soon after, seafarers began visiting it to slaughter fur seals,
elephant seals, and penguins. Among the passengers on the visiting ships
were rats and mice. To counter them, the sailors in 1818 brought in cats
and later rabbits to provide a food source for stranded seamen.
The cats fed on rabbits and native birds, exterminating two species
of birds. The number of rabbits swelled to 130,000 by the 1970s and
were stripping bare the island's vegetation. To counter this, scientists in
1968 introduced the myxomatosis virus, which is lethal to rabbits, and
the European rabbit fl ea, which spreads it. By the early 1980s, the popu-
lation of rabbits had fallen to about 20,000.
But the cats were hungry and began feeding on burrowing sea birds,
threatening their existence. So researchers began shooting the cats, and
by 2000, there were none left. With the cats gone, the rabbits began
proliferating again despite the presence of the virus. By 2009, they had
stripped as much as 40 percent of the island bare of vegetation. With
much of the soil's stabilizing vegetation gone, landslides are increasing,
one of which wiped out part of an important penguin colony.
Scientists' only course of action to prevent a possible ecosystem melt-
down is to eradicate the remaining rabbits, mice, and rats. The cost
estimate for this “solution” is at least $16 million and will take years.
The destruction of Macquarie Island is one of a large number of
environmental examples of what is popularly known as the law of unin-
tended consequences, which says, in effect, that knowledge is always
incomplete and that unforeseen things are likely to happen after people
start projects with good intentions. All purposeful actions will produce
some unintended consequences.
Other environmental examples of the law of unintended consequences
that are perhaps better known to Americans include the ethanol craze,
initiated to decrease America's dependence on foreign oil, reduce tailpipe
emissions from cars, and support agriculture. The major unintended
effect, which certainly should have been foreseen, was a massive decrease
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