Mischievous Species Capitalize on Globalization
Barry James International Herald Tribune
Monday, May 21, 2001
PARIS Invading "aliens" are costing the global economy possibly hundreds of billions of dollars every
year as well as spreading diseases and causing massive ecological destruction, yet no one is doing
much about it. Environmental scientists say this invasion is among the costliest but least understood
aspects of globalization.
If this were an invasion from space, governments would be alarmed. But these are not
extraterrestrials. They are ordinary animals, plants and insects that have escaped from their normal
environment to wreak havoc someplace else.
Consider these examples:
•A poisonous brown tree snake from Australia and Indonesia has exterminated most of the native
forest birds on Guam and is spreading across the Pacific, sometimes by hopping a ride in the wheel
well of aircraft.
•The Indian mongoose was introduced to the West Indies to control rats, but it has wiped out many
native species of birds, reptiles and amphibians. It also carries rabies.
•Crazy ants, proliferating in Asia, are indirectly destroying the rain forest on Christmas Island by
exterminating land crabs that play an important role in the ecosystem. In one 18-month period, the
ants were estimated to have killed 3 million crabs.
. Globalization is dramatically increasing the opportunities for plants and animals to get from where
they form a normal part of the flora and fauna to other places where they can become destructive
pests, weeds and parasites, either because people deliberately introduce new species such as
exotic fish and plants, or because the invaders slip in aboard aircraft, ships and containers.
And just ahead are transgenic species, such as oversized salmon, that some scientists warn could
elbow out their cousins.
The World Conservation Union in Gland, Switzerland, says awareness of the problems caused by
invasive alien species is "alarmingly low," and is seeking to shine some light on a problem it says
has "devastating consequences for the planet."
The union, which brings together 78 states and some 10,000 scientists, is using World Biodiversity
Day on May 22 to draw the attention of governments and the public to the threat posed to native
species and ecosystems by biological invasion. "The emphasis will be on how to cope with this alien
invasion, not from Mars but from our own planet," said Jeffrey McNeely, the organization's chief
scientist.
He said in an interview that economic losses caused by alien invaders probably cost several
hundred billions of dollars every year, in addition to the irreparable loss of thousands of native
species. "It is not just a problem for the world's ecology, but it is closely linked with global trade and
public health," he said, arguing that species invasion should be more carefully considered under
world trade rules.
The harm caused by alien species is "externalized" in considerations of the costs of global trade, he
said. Because the line of responsibility is insufficiently clear to bring about the necessary changes in
behavior, the general public or future generations have to pay the bill.
In a new book, "The Great Reshuffling," Mr. McNeely says that the impact of trade on biodiversity
remains poorly addressed. For centuries, native species developed behind oceans and mountains
but the modern explosion of travel and trade coupled with weakening customs and quarantine
controls means that alien invasion is reaching epic proportions.
About 20 percent of the species in the United States are considered invasive and harmful. They
have been introduced either deliberately for economic gain, or inadvertently, such as zebra mussels
let loose in the Great Lakes via ship ballast water, Asian tiger mosquitos brought in through used
tire imports and Chinese longhorn beetles that hopped a ride in the timber of shipping pallets or
containers and are threatening North American forests. In turn, China imported grass from the
United States for golf courses, which is spreading like wildfire.
The invaders don't just move in. They often entirely take over environments and proliferate at an
alarming rate because they are bigger or more aggressive than the local species and find no
predators to keep their numbers under control.
Mr. McNeely cited the foot and mouth disease in Britain as an example of an alien invasion, in which
an Asian virus finding no natural defenses was able to propagate at an alarming rate.
Mr. McNeely warned that global warming would increase health dangers from alien invaders.
Already doctors are turning up cases of malaria and other tropical diseases in the vicinity of airports
in countries where these do not normally exist.
These are some other examples:
•Caulerpa seaweed, believed to have been dumped from the tanks of the Monaco aquarium, has
proliferated throughout the northern Mediterranean and poses a serious threat to marine life.
•An ornamental tree from South America called Miconia, planted in a botanical garden in Tahiti in
the 1930s, now covers much of the island, deplacing native trees and contributing to a serious
problem of landslides and soil erosion.
•The South American water hyacinth, which is known to double in as little as 12 days, has invaded
at least 50 countries, killing off fish and limiting boat traffic.
A current debate in the United States over introducing the Asian black carp characterizes the debate
between economic interests and the broader but less clearly defined interests of the community and
the environment.
Fish farmers want to introduce the black carp to control a parasite called yellow grub that is spread
by mollusks and infects commercially reared catfish, bass and bluegill. The black carp, which grow
to more than a meter (39 inches) in length, live on mollusks.
But environmentalists fear that the black carp will escape and gobble up mollusks in the Mississippi
and other rivers, depriving native species of their food supply. Already, other species of carp that
were introduced for weed control and then escaped and proliferated in the Mississippi have muscled
out many of the local fish.
What happened in Lake Victoria in Africa should be a warning. Fishermen introduced the Nile perch
into the lake in the 1950s to counteract a drop in native species caused by overfishing. Since then
the voracious perch has eliminated more than 200 local species, half of them unique to the lake, by
preying on them and competing for food. The perch's flesh is oily, meaning that more trees have
had to be cut down to fuel fires to dry the catch. The ensuing runoff of soil into the lake increased
nutrient levels and allowed algae and water hyacinth to proliferate. This depleted the oxygen level in
the water and killed off more fish.
The result has been catastrophic not only for the environment but for the communities that used to
make their living from the lake, according to the World Conservation Union.
The example is a typical case of weighing the economic interests of the few against broader
environmental concerns, an argument that scientists say the public interest usually loses.
"It is true that great economic benefits a year in export income are flowing to a few people from the
introduction of the perch, but none of the money is being spent on managing the considerable
economic and ecological cost imposed on the poor or on the Lake Victoria ecosystem," Mr. McNeely
said.
Often people can't see the danger. Italy had to abandon a project to exterminate the north American
gray squirrel because people think of the rodent as cuddly, even though it is an agricultural pest and
has driven the European red squirrel to near extinction. The ordinary house cat also ranks among
the most predatory of the invaders, according to Peter Jackson, a retired expert on felines. "This is
not often taken into account," he said.
Not only can cats quickly revert to the wild, where they become formidable hunters and killers, but
domestic pets cause enormous depredations during their nocturnal ramblings. Judging from a
survey by the Mammal Society in Britain, cats could be killing more than 250 million birds and other
creatures in the United Kingdom every year.
The society says the toll could be significantly reduced if owners kept their cats indoors at night or
put a loud bell on their collar.
Many aliens eventually become naturalized, like potatoes and tomatoes. Others are creatures that
Noah might wish he had never allowed onto the ark, such as the Rosy wolf snail, the crazy ant and
the walking catfish.
But there is one species, Mr. McNeely says, that is more invasive than all the others put together.
It's called homo sapiens.