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Great Lakes Article:

Exotic Species Swallow Nation:

As Alien Invaders Proliferate, Conservationists Change Their Focus

New York Times


In a human-dominated planet, it is only natural that wilderness and wildlife will be increasingly disrupted, hemmed in or exterminated.

That has been happening steadily through the era of industrialization, which created today's wealthy minority, and will happen far more, biologists say, as the developing world strives to become developed.

In the face of this trend, conservationists and scientists have tried a host of strategies to preserve the world's shrinking mosaic of untrammeled ecosystems: establishing parks; pushing for laws protecting endangered species; publicizing "biodiversity hot spots," places where wilderness and people dangerously overlap.

But on almost every front, they find themselves falling back, like an army under surprise attack from within and without. Nothing is simple any more, many scientists lament. Even the definition of "wild" is open to debate.

With some species fading and others in transit, the experts have to decide simultaneously which wildlife to protect and which to get rid of.

Accelerating trade and migration have resulted in large-scale invasions of islands and continents by new species and the disruptions of longstanding ecological regimes that many naturalists have long treasured. An entire field, restoration ecology, has arisen to defend "native" species against "alien" invaders.

Hawaii's birds exemplify the problem, falling to extinction one by one, besieged by pigs, rats, cats and other imports.

On the East Coast, marshes of native cordgrass have become overgrown with an exotic species, the common reed. Restoration ecologists had once hoped to return these marshes to a self-sustaining population of cordgrass, but have instead been fighting a continuous and, some say, losing battle against the hardy reed.

`'You have to keep herbiciding," said Dr. Joy B. Zedler, a restoration ecologist at the University of Wisconsin. "You have to keep spraying it year after year, and the minute you stop it'll come back in."

So a growing chorus of biologists is proposing a new approach to the fast-blending biosphere. They say change should be accepted as largely inevitable and choices for managing nature should be based on what is desirable and undesirable, not what is native and foreign.

Altogether, researchers estimate that 50,000 species have invaded the United States as a result of human activities. North America, as a result, has 20 percent more plant species now than it did before colonization, biologists say.

"They're not going back," said Dr. Mark A. Davis, an ecologist at Macalester College in St. Paul who has been exhorting colleagues to stop viewing nonnatives as necessarily bad since, he says, most are harmless.

He suggests accepting these species as the new immigrants a biological reflection of the same globalization affecting economies, societies and information.

"It's never-ending to try to keep a habitat pure," he said, "You're fighting natural processes at some point."

But many of his fellow ecologists are appalled.

"If we ignore this, it gets us gypsy moths and chestnut blight and any number of other ecological disasters that greatly reduce our flexibility for future options and reduce the beauty of the natural world," said Dr. Guy McPherson, an ecologist at the University of Arizona, echoing others.

Some 400 of the 1,000 or so species that are listed as endangered are thought to be at risk, primarily because of competition or predation from nonnative species, Dr. McPherson added.

While that is indeed thought to be the case, Dr. Davis said, few rigorous studies document such effects.

Dr. Davis said the real villain driving extinction rates around the world was loss of habitat. Instead of focusing on native or alien, Dr. Davis said, humans should start becoming comfortable with controlling the textures of ecosystems based on what works ecologically, aesthetically, or otherwise -- and what does not.

He noted that nest-robbing brown-headed cowbirds are native to North America, as are hantavirus and Lyme disease.

"Native versus exotic doesn't make ecological sense," he said. "It doesn't make practical sense, and it drives a lot of attention and energy away from really important problems we should be addressing."

The most pressing question for many conservationists is what species or habitat to save.

Often, they rely on sheer numbers to make the tough decisions.

Following the simple rule that more is better, conservationists are giving highest priority to biodiversity hot spots those places that are rich in species and often lush and beautiful. The strategy was refined by Conservation International, an influential private group in Washington.

But now some scientists have begun to challenge even this once unassailable formula. `'Biodiversity hot spots are just places with a lot of unique plant species," said Dr. Peter Kareiva, a lead scientist at the Nature Conservancy. He has been urging conservationists to look beyond simple species counts when deciding how to dispense limited resources.

"You have to be mindful of uniqueness," Dr. Kareiva said. "Look at biodiversity cold spots and you'll find they're pretty valuable to people, like the Serengeti or all of Alaska."

After important habitat is identified, another problem confronts battle-weary scientists and officials seeking to hold back bulldozers, chain saws and fishing nets.

Instead of just establishing parks, building fences and hiring guards, some conservationists are moving to something akin to conservation judo, they say, using the power of their opponents to their own advantage.

Last year, for example, surveys by the World Conservation Union and Future Harvest, a group promoting traditional agriculture, found that half the world's 17,000 major wildlife refuges were being heavily used for agriculture. In fact, the survey found, some reserves actually attract impoverished settlers seeking land.

These findings have convinced some conservation biologists that they should work with farmers to preserve some habitat and find ways to prevent wildlife from consuming crops.

"To avert widespread extinctions and feed the world, we must integrate biodiversity preservation into all landscapes from grazing lands to coffee plantations to rice paddies," said Jeffrey A. McNeely, the chief scientist at the World Conservation Union.

This integration can be as simple as establishing windbreaks of trees between dairy pastures, as has been done in Costa Rica. The rows of trees serve as corridors for the passage of wildlife.

In the seas, similar efforts are under way. Fishermen in St. Lucia in the Caribbean initially opposed the establishment of protected marine reserves along some coasts but now support the project because catches in adjacent fishable waters have risen 30 percent or more.

Meanwhile, though, scientists seeking to preserve wild things on an increasingly modified earth struggle to define their goals, when native wildlife increasingly mixes with introduced, farmed or hybridized varieties.

Many of the Florida panthers that prowl in state refuges are no longer pure but instead a result of crossbreeding with Western mountain lions.

Ranching groups in the West have petitioned the Fish and Wildlife Service to remove gray wolves from the federal list of endangered species because many may actually be mixed breeds of wolves and coyotes. The red wolf in the Southwest has come under similar scrutiny.

In the Pacific Northwest, fights have sprung up around salmon species that are protected by states and the federal government, while those same species are being bred in fish hatcheries.

The protections come with real costs, with farmers denied water and loggers denied access to forests. The new debate has repeatedly landed wildlife scientists in court, defending or attacking decisions about what is rare, what is special, what should be saved.

Which leads to yet another question: who decides what is special? If left to a majority, weaned on the Discovery Channel and National Geographic, the wild world of the future may end up looking cuddly and cute still populated with pandas and other so-called charismatic megafauna but may not have much biological integrity deep down. Ecologists say that ecosystems are often built on the backs of creatures that can only be called uncharismatic microfauna.

In many ways, some conservation biologists say, this spate of new challenges is just the next step in the maturing of this still relatively young field. In what some are referring to as the conceptual adolescence of conservation, researchers are beginning to get away from simplistic notions of a return to an untampered wilderness and instead starting the harder journey toward a future of human choices, intervention and management.

"Conservation biologists are too romantic," Dr. Kareiva said. "They think what's good is what's natural. Let's be serious. A better vision is something that functions and has habitat quality and aesthetic quality. We have to ask, What do we want the natural world to look like 100 years from now?"

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