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12-10-2003, 08:14 AM
http://www.oregonlive.com/printer/printer.ssf?/base/science/1070974558301740.xml
Effort against extinction
The 30-year-old federal Endangered Species Act, long under attack, now includes 1,200 species, 24 of which are in Oregon
12/10/03
JOE ROJAS-BURKE
Five times in the history of Earth, catastrophic forces cleared the planet of a large fraction of living things.
An unstable global climate veered through ice ages. Giant asteroids smashed into the planet. Whole branches of the tree of life disappeared from the fossil record, taking out the dinosaurs and great winged reptiles as well as woolly mammoths and other giant mammals last seen in North America about 11,000 years ago.
A sixth mass extinction is under way, driven by humankind's exponential population growth and expanding use of land and sea. Thirty years ago this month, the emerging crisis drove Congress to pass the broadest and most powerful wildlife protection law in U.S. history -- the Endangered Species Act of 1973. Its urgent goals: to fend off further extinctions; to restore imperiled species to self-sustaining abundance; and to protect the prairies, mountains, lakes, streams and other habitat needed to sustain wildlife.
The noble sentiment attracted almost universal support, at first. Richard Nixon, the Republican president who signed the bill into law, said existing federal law "simply does not provide the kind of management tools needed to act early enough to save a vanishing species."
Such broad-based appeals for the strong arm of federal regulation didn't last once courts began to act.
The pivotal decision came in 1978, when the Supreme Court halted work on a federal dam in Tennessee to protect the stream habitat of a little-known but soon-to-be-famous fish, the snail darter. Three words from the ruling have echoed loudly: that Congress unequivocally intended the act to halt and reverse the loss of species "whatever the cost."
In that spirit, federal agencies and courts have cut off irrigation to Klamath Basin farmers to protect sucker fish, banned logging across the Northwest for the sake of northern spotted owls, blocked subdivisions in Texas because of conflicts with golden-cheeked warblers, and delayed building a university campus and extending interstate highways in Southern California to consider the needs of threatened inhabitants of vernal pools.
Lawsuits have escalated to near paralyzing levels, according to the nation's lead agency for protecting species, the U.S. Fish and Wildlife Service. Political fights have deadlocked Congress, preventing reauthorization of the act since 1988, although annual funding has continued. The Bush administration has labeled the act "broken."
On the act's 30th anniversary, The Oregonian examines the status of the growing list of threatened and endangered species, and the prospects for thwarting the Earth's sixth mass extinction:
Is the effort working? Raw numbers make the effort to prevent extinctions look like a desperate rear-guard action.
Every year, about 3,000 species go extinct worldwide. Some estimates put the number wiped out as high as 30,000 a year. At these rates, scientists figure the planet could lose half its varieties of life in the next 1,000 years.
Under the Endangered Species Act, 16 animals and plants have made spectacular comebacks and are deemed recovered. Among them: gray whales, American alligators, peregrine falcons, Aleutian Canada geese, the Atlantic coast population of brown pelicans, and the Douglas County group of Oregon's Columbian white-tailed deer, which was de-listed just this year.
"The agency people are doing a heck of a job with the limited resources they have," says J. Michael Scott, a wildlife biology professor at the University of Idaho. He is co-organizer of a national conference on the Endangered Species Act in November at the University of California in Santa Barbara.
"The number of species that are recovering or stable, that's close to 50 percent," Scott says.
But for each recovery in the past three decades, 126 species have qualified as threatened or endangered in the United States. The total number of listed species has climbed to more than 1,200.
The act's greatest success has been preventing the extinction of listed species, says Bob Irvin, director of conservation in the United States for the World Wildlife Fund. Although seven protected species have vanished since the law took effect, conservation biologists say many more would have been lost without the act. One independent scientific analysis concluded that the law has probably saved 192 species from annihilation.
Many are battling back from near zero. One example is in southeastern Oregon: Livestock grazing and prescribed burning of vegetation reduced the range of the Malheur wire lettuce, a spindly plant with delicate white flowers, to a single plot discovered in 1966. Nonnative cheatgrass later invaded the site and displaced every known wire-lettuce plant. Seeds, previously collected and preserved, prevented extinction.
Do lost species matter?
A world without wire lettuce or fairy shrimp might be less interesting. But how much does it matter?
One possibility: that extinctions are comparable to the yanking of parts from an airplane in midflight. At some point, it will crash.
"We are reaching into the hood of our Earth-engine and pulling parts out," says Shahid Naeem, a Columbia University zoologist. "We don't really know what the consequences of losing these parts will be."
He adds, "Do you really want to take this planet on its journey through the next century with 50 percent of its parts?"
As components of an ecosystem, many species work together -- in ways barely understood -- to provide essential services, says Brian Czech, a wildlife biologist at Virginia Polytechnic Institute and State University.
Wetlands filter and purify water; scavengers and decomposers recycle nutrients and enrich soils; insects pollinate, and birds distribute seeds for the plants that sit at the base of food webs, turning sunlight into fuel.
Perhaps a drastically reduced set of species could provide the basic "ecosystem services" needed to support people. Wolves are making a tentative comeback. Deer, beaver and Canada geese are thriving alongside people, not to mention raccoons, starlings and many cosmopolitan weeds.
"Nobody's got a firm grasp of how much biodiversity is required to maintain human economies," Czech says.
The past offers some guidance. Many experts now agree that starting about 40,000 years ago, Stone Age people helped wipe out most of the Earth's large land animals, from the 600-pound claw-footed kangaroo of Australia to the mammoths and cattle-sized ground sloths of North America.
Despite the loss, ecosystems continued to function, says Martin Jenkins, a scientist with the U.N. Environment Program, in a recent essay in the journal Science. Jenkins points to New Zealand, where people have extirpated 29 of the 38 species of flightless bird and nearly zeroed out the remaining species -- without destabilizing the ecosystem.
"There is little evidence to dissuade us from the view that what applies for New Zealand today could equally hold more or less for the world as a whole tomorrow," Jenkins concludes.
Some scientists think humans have a basic ethical responsibility to protect endangered species, even if they appear to provide no unique ecosystem services or contain no valuable pharmaceutical compounds.
"I didn't put them on the planet. Neither did anyone else I know, so from an ethical standpoint, we shouldn't eliminate them," says Scott, the University of Idaho professor.
But at what cost today? People have paid a big price for preventing extinctions. Ask timber workers, Klamath Basin farmers and hydroelectric power generators in the Northwest, a hot spot for recent conflicts.
Following the listing of the northern spotted owl in 1990, a federal court halted logging in owl habitat on federal land. The timber supply from federal forests fell from about 5 billion board feet to about 1 billion board feet in three years. Oregon and Washington lost about 19,000 forestry jobs by 1995, although foreign competition and corporate restructuring also played a role.
To shield endangered Klamath Basin suckers from a worsening drought, federal officials in 2002 halted irrigation to about 1,200 farms -- bringing an estimated net loss of $27 million to $46 million in crop revenues, of which taxpayers covered about $30 million in emergency payments.
Every year in the Columbia River hydropower system, federal agencies striving to rebuild depleted salmon and steelhead runs spend about $400 million, not counting power generation forgone to protect migrating fish, which costs about $300 million a year, according to the Bonneville Power Administration.
Some economists lately have started asking questions about the value of natural habitat and have found that conservation can more than offset forgone payoffs from, say, trees left standing, or coral reefs spared from bottom-scraping trawl nets.
"What we lack is a long-term perspective," Naeem says. He and several co-authors recently published an analysis of results from several case studies.
One study compared three uses of forests in Cameroon: low-impact logging, conversion to rubber tree and oil palm plantations, and conversion to farming. Maintaining the forest for low-impact logging added up to the best value after taking into account services forests provide: preventing erosion and keeping streams clear, controlling floods, and providing habitat for economically valuable plants and animals. Converting to plantation lowered total value to a net loss.
Economic worth of habitat Another study focused on wetlands in Canada. Converting them to farms yielded total economic benefits, but intact wetlands offered a 60 percent greater value from hunting, fishing, trapping and other services. Other studies reached similar conclusions about the value of protecting tropical mangrove forests from conversion to shrimp farms and protecting coral reefs from destructive fishing.
Naeem and co-authors came up with a global estimate of the cost of habitat lost each year: about $250 billion.
But if it's so valuable, why are people converting it to other uses? For one thing, the researchers say landowners and businesses can take short-term profits without incurring the long-term costs of the loss of services provided by a forest or wetland.
Sometimes government subsidies shield land developers from the costs. For instance, U.S. taxpayers spend about half a billion dollars a year supplying water to farms and ranches of the arid West.
Considering the economic value of natural habitats, environmental groups and many scientists say we are spending far too little on conservation. The U.S. Fish and Wildlife Service received $268 million to carry out the endangered species program in 2003, including $65.8 million for the recovery of endangered and threatened species.
Divided among the listed species, spending is about 17 percent of the amount Fish and Wildlife recovery plans call for, according to Scott. Spending per listed species has fallen to about three-quarters of its high point in 1978, he says. The service is struggling to deal with a massive backlog of critical habitat designations, which have spawned a growing docket of lawsuits from environmental groups and countersuits by industry groups.
Would more money help? The Bush administration's top official for Fish and Wildlife says the government can improve its recovery efforts without spending more money.
"The balance has been weighted too heavily toward a regulatory approach and not enough toward a collaborative approach," says Craig Manson, assistant secretary for Fish and Wildlife and Parks in the U.S. Department of the Interior.
The White House's proposed budget for 2004 called for cutting recovery spending by more than $3 million, while it would increase overall endangered species funding by about $4 million. Manson said the Fish and Wildlife Service needs to focus more on strategies that will keep species off the list and better balance spending on listed animals and plants.
In some years, half to three-quarters of spending on recovery have gone to a charismatic group of just 10 species, including the bald eagle, the grizzly bear, the Florida panther and the northern spotted owl.
But some researchers insist that funding recovery plans more fully would make a significant difference. Evidence comes from a recent analysis by Judith Miller of the University of Montana and others. The researchers compared actual spending per species as a ratio of the amount requested for recovery by field biologists. The higher the ratio, the more likely the species was improving.
"We can make a difference if we get serious about funding," says Scott, who was a co-author of the study, published last year in the journal BioScience.
What needs to change? After 30 years of conflict, scientists and conservation groups increasingly are courting the cooperation of ranchers, farmers and business.
"Lawsuits have succeeded in tying the agency in knots, and conservation is suffering," says the World Wildlife Fund's Irvin. "After a decade of deadlock, it is time to try a new approach."
Most of the land needed by endangered species is in private hands. Irvin's group and Environmental Defense, another influential conservation organization, are lobbying for more incentives to encourage landowners and companies to volunteer to protect and restore habitat.
Ecologist Michael Rosenzweig of the University of Arizona is rallying scientists with a similar message and a catchy phrase: "reconciliation ecology."
Rosenzweig, author of the book "Win-Win Ecology," argues that we can design our cities, roads, farms and ranches so they meet our needs but also support diverse and wild nature. We have to do this, he says, because setting aside more wildlife refuges will fail to save a majority of threatened wildlife.
"If we set aside as much as 20 percent of the Earth's surface, we're still going to lose as much as 80 percent of the Earth's species," he says.
Some scientists and conservation groups insist that we face a more fundamental conflict with nature. They see no end to habitat loss and mass extinction unless we greatly slow our population growth, development of land and consumption of energy and other resources.
Fraser Shilling, a scientist at the University of California at Davis, says the call for collaborative approaches amounts to more sacrificing of wild landscapes for the sake of developers. He points to the habitat conservation plans promoted by President Clinton's Interior secretary, Bruce Babbitt. Under the policy, the Fish and Wildlife Service can give landowners permits for construction or other projects that harm listed species. In return, landowners must carry out a habitat conservation plan to minimize harm "to the maximum extent practicable."
Scientists including Rosenzweig and Scott, and conservation groups such as Environmental Defense look favorably on the approach. Manson says the Bush administration wants to extend the idea to include more landowners.
Shilling says, "There is no reason why you should build a subdivision on top of endangered species habitat."
Lessons from past extinctions Scientists in recent years have begun trying to figure out what future life will be like after mass extinction.
The five catastrophic events recorded in the fossil record provide some clues. As a general rule, the survivors tended to be a vastly reduced set of weedy generalists. But the exit of so many players sets the stage for the rapid evolution of a rich variety of replacements, including the mammals that took over where dinosaurs left off.
Of course, it takes several million years for evolution to rediversify a planet. And this time around, there are a few hitches.
"Every other mass extinction has been a blip," Rosenzweig says. "It's different this time. We are not going away."
The human actions behind the current extinctions are striking hardest at the planet's biodiversity hot spots -- tropical forests, wetlands, estuaries and coral reefs -- the wellsprings of new varieties of life for the past 250 million years. As it stands, even the largest protected refuges are too small, experts say, to allow remnant populations of elephants, rhinoceroses, gorillas and other large animals to diversify into new forms.
As Edward O. Wilson of Harvard University has put it, the decimation of species and destruction of natural habitats could be the legacy that our descendants are least likely to forgive.
Joe Rojas-Burke: 503-412-7073, joerojas@news.oregonian.com.
Effort against extinction
The 30-year-old federal Endangered Species Act, long under attack, now includes 1,200 species, 24 of which are in Oregon
12/10/03
JOE ROJAS-BURKE
Five times in the history of Earth, catastrophic forces cleared the planet of a large fraction of living things.
An unstable global climate veered through ice ages. Giant asteroids smashed into the planet. Whole branches of the tree of life disappeared from the fossil record, taking out the dinosaurs and great winged reptiles as well as woolly mammoths and other giant mammals last seen in North America about 11,000 years ago.
A sixth mass extinction is under way, driven by humankind's exponential population growth and expanding use of land and sea. Thirty years ago this month, the emerging crisis drove Congress to pass the broadest and most powerful wildlife protection law in U.S. history -- the Endangered Species Act of 1973. Its urgent goals: to fend off further extinctions; to restore imperiled species to self-sustaining abundance; and to protect the prairies, mountains, lakes, streams and other habitat needed to sustain wildlife.
The noble sentiment attracted almost universal support, at first. Richard Nixon, the Republican president who signed the bill into law, said existing federal law "simply does not provide the kind of management tools needed to act early enough to save a vanishing species."
Such broad-based appeals for the strong arm of federal regulation didn't last once courts began to act.
The pivotal decision came in 1978, when the Supreme Court halted work on a federal dam in Tennessee to protect the stream habitat of a little-known but soon-to-be-famous fish, the snail darter. Three words from the ruling have echoed loudly: that Congress unequivocally intended the act to halt and reverse the loss of species "whatever the cost."
In that spirit, federal agencies and courts have cut off irrigation to Klamath Basin farmers to protect sucker fish, banned logging across the Northwest for the sake of northern spotted owls, blocked subdivisions in Texas because of conflicts with golden-cheeked warblers, and delayed building a university campus and extending interstate highways in Southern California to consider the needs of threatened inhabitants of vernal pools.
Lawsuits have escalated to near paralyzing levels, according to the nation's lead agency for protecting species, the U.S. Fish and Wildlife Service. Political fights have deadlocked Congress, preventing reauthorization of the act since 1988, although annual funding has continued. The Bush administration has labeled the act "broken."
On the act's 30th anniversary, The Oregonian examines the status of the growing list of threatened and endangered species, and the prospects for thwarting the Earth's sixth mass extinction:
Is the effort working? Raw numbers make the effort to prevent extinctions look like a desperate rear-guard action.
Every year, about 3,000 species go extinct worldwide. Some estimates put the number wiped out as high as 30,000 a year. At these rates, scientists figure the planet could lose half its varieties of life in the next 1,000 years.
Under the Endangered Species Act, 16 animals and plants have made spectacular comebacks and are deemed recovered. Among them: gray whales, American alligators, peregrine falcons, Aleutian Canada geese, the Atlantic coast population of brown pelicans, and the Douglas County group of Oregon's Columbian white-tailed deer, which was de-listed just this year.
"The agency people are doing a heck of a job with the limited resources they have," says J. Michael Scott, a wildlife biology professor at the University of Idaho. He is co-organizer of a national conference on the Endangered Species Act in November at the University of California in Santa Barbara.
"The number of species that are recovering or stable, that's close to 50 percent," Scott says.
But for each recovery in the past three decades, 126 species have qualified as threatened or endangered in the United States. The total number of listed species has climbed to more than 1,200.
The act's greatest success has been preventing the extinction of listed species, says Bob Irvin, director of conservation in the United States for the World Wildlife Fund. Although seven protected species have vanished since the law took effect, conservation biologists say many more would have been lost without the act. One independent scientific analysis concluded that the law has probably saved 192 species from annihilation.
Many are battling back from near zero. One example is in southeastern Oregon: Livestock grazing and prescribed burning of vegetation reduced the range of the Malheur wire lettuce, a spindly plant with delicate white flowers, to a single plot discovered in 1966. Nonnative cheatgrass later invaded the site and displaced every known wire-lettuce plant. Seeds, previously collected and preserved, prevented extinction.
Do lost species matter?
A world without wire lettuce or fairy shrimp might be less interesting. But how much does it matter?
One possibility: that extinctions are comparable to the yanking of parts from an airplane in midflight. At some point, it will crash.
"We are reaching into the hood of our Earth-engine and pulling parts out," says Shahid Naeem, a Columbia University zoologist. "We don't really know what the consequences of losing these parts will be."
He adds, "Do you really want to take this planet on its journey through the next century with 50 percent of its parts?"
As components of an ecosystem, many species work together -- in ways barely understood -- to provide essential services, says Brian Czech, a wildlife biologist at Virginia Polytechnic Institute and State University.
Wetlands filter and purify water; scavengers and decomposers recycle nutrients and enrich soils; insects pollinate, and birds distribute seeds for the plants that sit at the base of food webs, turning sunlight into fuel.
Perhaps a drastically reduced set of species could provide the basic "ecosystem services" needed to support people. Wolves are making a tentative comeback. Deer, beaver and Canada geese are thriving alongside people, not to mention raccoons, starlings and many cosmopolitan weeds.
"Nobody's got a firm grasp of how much biodiversity is required to maintain human economies," Czech says.
The past offers some guidance. Many experts now agree that starting about 40,000 years ago, Stone Age people helped wipe out most of the Earth's large land animals, from the 600-pound claw-footed kangaroo of Australia to the mammoths and cattle-sized ground sloths of North America.
Despite the loss, ecosystems continued to function, says Martin Jenkins, a scientist with the U.N. Environment Program, in a recent essay in the journal Science. Jenkins points to New Zealand, where people have extirpated 29 of the 38 species of flightless bird and nearly zeroed out the remaining species -- without destabilizing the ecosystem.
"There is little evidence to dissuade us from the view that what applies for New Zealand today could equally hold more or less for the world as a whole tomorrow," Jenkins concludes.
Some scientists think humans have a basic ethical responsibility to protect endangered species, even if they appear to provide no unique ecosystem services or contain no valuable pharmaceutical compounds.
"I didn't put them on the planet. Neither did anyone else I know, so from an ethical standpoint, we shouldn't eliminate them," says Scott, the University of Idaho professor.
But at what cost today? People have paid a big price for preventing extinctions. Ask timber workers, Klamath Basin farmers and hydroelectric power generators in the Northwest, a hot spot for recent conflicts.
Following the listing of the northern spotted owl in 1990, a federal court halted logging in owl habitat on federal land. The timber supply from federal forests fell from about 5 billion board feet to about 1 billion board feet in three years. Oregon and Washington lost about 19,000 forestry jobs by 1995, although foreign competition and corporate restructuring also played a role.
To shield endangered Klamath Basin suckers from a worsening drought, federal officials in 2002 halted irrigation to about 1,200 farms -- bringing an estimated net loss of $27 million to $46 million in crop revenues, of which taxpayers covered about $30 million in emergency payments.
Every year in the Columbia River hydropower system, federal agencies striving to rebuild depleted salmon and steelhead runs spend about $400 million, not counting power generation forgone to protect migrating fish, which costs about $300 million a year, according to the Bonneville Power Administration.
Some economists lately have started asking questions about the value of natural habitat and have found that conservation can more than offset forgone payoffs from, say, trees left standing, or coral reefs spared from bottom-scraping trawl nets.
"What we lack is a long-term perspective," Naeem says. He and several co-authors recently published an analysis of results from several case studies.
One study compared three uses of forests in Cameroon: low-impact logging, conversion to rubber tree and oil palm plantations, and conversion to farming. Maintaining the forest for low-impact logging added up to the best value after taking into account services forests provide: preventing erosion and keeping streams clear, controlling floods, and providing habitat for economically valuable plants and animals. Converting to plantation lowered total value to a net loss.
Economic worth of habitat Another study focused on wetlands in Canada. Converting them to farms yielded total economic benefits, but intact wetlands offered a 60 percent greater value from hunting, fishing, trapping and other services. Other studies reached similar conclusions about the value of protecting tropical mangrove forests from conversion to shrimp farms and protecting coral reefs from destructive fishing.
Naeem and co-authors came up with a global estimate of the cost of habitat lost each year: about $250 billion.
But if it's so valuable, why are people converting it to other uses? For one thing, the researchers say landowners and businesses can take short-term profits without incurring the long-term costs of the loss of services provided by a forest or wetland.
Sometimes government subsidies shield land developers from the costs. For instance, U.S. taxpayers spend about half a billion dollars a year supplying water to farms and ranches of the arid West.
Considering the economic value of natural habitats, environmental groups and many scientists say we are spending far too little on conservation. The U.S. Fish and Wildlife Service received $268 million to carry out the endangered species program in 2003, including $65.8 million for the recovery of endangered and threatened species.
Divided among the listed species, spending is about 17 percent of the amount Fish and Wildlife recovery plans call for, according to Scott. Spending per listed species has fallen to about three-quarters of its high point in 1978, he says. The service is struggling to deal with a massive backlog of critical habitat designations, which have spawned a growing docket of lawsuits from environmental groups and countersuits by industry groups.
Would more money help? The Bush administration's top official for Fish and Wildlife says the government can improve its recovery efforts without spending more money.
"The balance has been weighted too heavily toward a regulatory approach and not enough toward a collaborative approach," says Craig Manson, assistant secretary for Fish and Wildlife and Parks in the U.S. Department of the Interior.
The White House's proposed budget for 2004 called for cutting recovery spending by more than $3 million, while it would increase overall endangered species funding by about $4 million. Manson said the Fish and Wildlife Service needs to focus more on strategies that will keep species off the list and better balance spending on listed animals and plants.
In some years, half to three-quarters of spending on recovery have gone to a charismatic group of just 10 species, including the bald eagle, the grizzly bear, the Florida panther and the northern spotted owl.
But some researchers insist that funding recovery plans more fully would make a significant difference. Evidence comes from a recent analysis by Judith Miller of the University of Montana and others. The researchers compared actual spending per species as a ratio of the amount requested for recovery by field biologists. The higher the ratio, the more likely the species was improving.
"We can make a difference if we get serious about funding," says Scott, who was a co-author of the study, published last year in the journal BioScience.
What needs to change? After 30 years of conflict, scientists and conservation groups increasingly are courting the cooperation of ranchers, farmers and business.
"Lawsuits have succeeded in tying the agency in knots, and conservation is suffering," says the World Wildlife Fund's Irvin. "After a decade of deadlock, it is time to try a new approach."
Most of the land needed by endangered species is in private hands. Irvin's group and Environmental Defense, another influential conservation organization, are lobbying for more incentives to encourage landowners and companies to volunteer to protect and restore habitat.
Ecologist Michael Rosenzweig of the University of Arizona is rallying scientists with a similar message and a catchy phrase: "reconciliation ecology."
Rosenzweig, author of the book "Win-Win Ecology," argues that we can design our cities, roads, farms and ranches so they meet our needs but also support diverse and wild nature. We have to do this, he says, because setting aside more wildlife refuges will fail to save a majority of threatened wildlife.
"If we set aside as much as 20 percent of the Earth's surface, we're still going to lose as much as 80 percent of the Earth's species," he says.
Some scientists and conservation groups insist that we face a more fundamental conflict with nature. They see no end to habitat loss and mass extinction unless we greatly slow our population growth, development of land and consumption of energy and other resources.
Fraser Shilling, a scientist at the University of California at Davis, says the call for collaborative approaches amounts to more sacrificing of wild landscapes for the sake of developers. He points to the habitat conservation plans promoted by President Clinton's Interior secretary, Bruce Babbitt. Under the policy, the Fish and Wildlife Service can give landowners permits for construction or other projects that harm listed species. In return, landowners must carry out a habitat conservation plan to minimize harm "to the maximum extent practicable."
Scientists including Rosenzweig and Scott, and conservation groups such as Environmental Defense look favorably on the approach. Manson says the Bush administration wants to extend the idea to include more landowners.
Shilling says, "There is no reason why you should build a subdivision on top of endangered species habitat."
Lessons from past extinctions Scientists in recent years have begun trying to figure out what future life will be like after mass extinction.
The five catastrophic events recorded in the fossil record provide some clues. As a general rule, the survivors tended to be a vastly reduced set of weedy generalists. But the exit of so many players sets the stage for the rapid evolution of a rich variety of replacements, including the mammals that took over where dinosaurs left off.
Of course, it takes several million years for evolution to rediversify a planet. And this time around, there are a few hitches.
"Every other mass extinction has been a blip," Rosenzweig says. "It's different this time. We are not going away."
The human actions behind the current extinctions are striking hardest at the planet's biodiversity hot spots -- tropical forests, wetlands, estuaries and coral reefs -- the wellsprings of new varieties of life for the past 250 million years. As it stands, even the largest protected refuges are too small, experts say, to allow remnant populations of elephants, rhinoceroses, gorillas and other large animals to diversify into new forms.
As Edward O. Wilson of Harvard University has put it, the decimation of species and destruction of natural habitats could be the legacy that our descendants are least likely to forgive.
Joe Rojas-Burke: 503-412-7073, joerojas@news.oregonian.com.