Copyright 1998 Stanley Foundation
World Press Review
November 1, 1998
THE COMING PLAGUES -- NON-NATIVE SPECIES ON THE MOVE DUE TO GLOBAL
Bob Holmes, "New Scientist" (weekly), London, April 18, 1998.
Invasions by alien species--already one of the most serious threats
to bio-diversity worldwide--are set to worsen in the next few
decades as the world continues to warm. "Without any question,
global change is going to exacerbate the problem," says Harold
Mooney, an ecologist at Stanford University in California, during
a symposium on invading species and global change.
The outcome will depend on regional variations in climate
change--something that climatologists still cannot predict with any
confidence. But almost everyone agrees that most regions of Earth
will get warmer, and this is likely to lead to more species
"It opens up the door to new exotic species that were totally
excluded from the environment," says James Carlton of Williams
College in Massachusetts. The tropical alga Caulerpa taxifolia, for
example, which invaded the Mediterranean Sea in the mid-1980s,
could move up the Atlantic coast of Europe if ocean temperatures
rise, he says. On land, a three-degree centigrade [5.4-degree
Fahrenheit] rise in average temperature could be enough to allow
the Mediterranean fruit fly, a major pest of citrus crops, to
spread northward into northern Europe, says Robert Sutherst of the
University of Queensland in Brisbane.
Warming could also cause problems among species that have been
intentionally introduced. British oyster farmers, for example, grow
Japanese oysters in coastal waters, but the species cannot
reproduce because the water is too cold. Warmer water could
transform it into a pest, as it already is in Australia. "I suspect
it would only take something like two or three degrees
[centigrade]," says Susan Utting of the Center for Environment
Fisheries and Aquaculture Science's lab in Conwy, Wales.
Climate changes may have more subtle effects. A longer growing
season may give some invading weedy plants time to flower and set
seed where previously they could only spread asexually. This
new-found ability could allow the weeds to adapt more quickly to
combat insects that eat them.
Rising levels of carbon dioxide in the atmosphere--the main
contributor to global warming--should favor plants that are able
to take advantage of the extra carbon dioxide to make more sugar
and therefore grow faster. One such species, at least in laboratory
experiments, is cheatgrass, an introduced species that now
dominates vast areas of the American West. Jeff Dukes, a biologist
at Stanford University, observes, "That's kind of ominous.
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