BOSTON — One of today's most contentious environmental issues - protection of endangered species - tends to generate alarmist comment by partisans on both sides.
Activists warn that the rate of extinction has accelerated to a level that is dangerously above normal. Critics of current protection laws say property rights are threatened by the prospect of zealots finding an endangered species in everybody's backyard.
Now, there is scientific evidence to support the notion that saving endangered species in the United States - while it remains a complicated and expensive job - would interfere with human activities in only a few, small places.
That's the good news, according to researchers at Princeton University and the Environmental Defense Fund (EDF).
The challenge is that most endangered plants and animals are concentrated near areas of high population and development. And in these hot spots of Hawaii, southern California, Florida, and parts of Appalachia, there is significant overlap of species in decline.
Or as EDF senior ecologist David Wilcove puts it, "Some of these species are living on some pretty pricey real estate."
Loss of habitat due to construction and farming is the greatest threat to plants and animals - particularly those that are endemic, or living only in a limited area. But the introduction of non-native species is a major problem as well.
According to a recent report by The Nature Conservancy, such alien species are responsible for the decline of 42 percent of the federally listed endangered or threatened species. Conservancy president John Sawhill points out that the cost of such invaders to agriculture, fishing, electrical utilities, tourism, and other industries is "staggering."
Perhaps the worst culprit in Hawaii is the feral pig, descended from domestic stock brought by settlers. The pigs are directly responsible for the destruction of many plant species, which in turn has led to erosion damaging to lakes and streams. Pigs also spread mosquitoes, which transmit diseases to native birds.
The Princeton-EDF researchers (whose findings are detailed in the current issue of Science magazine) tracked 924 endangered species in 2,858 counties throughout the United States. They found that most of the species groups (plants, mammals, birds, reptiles, etc.) are found on less than 2 percent of the country's land area - with many individual species restricted to a single county.
"The fact that species are clumped into hot spots obviously has implications for policy, for designing species-protection plans," says W. Mark Roberts, an evolutionary biologist at Princeton. "It's easier to protect species that are clumped into certain areas than it is to protect species that are distributed widely, because fewer areas are likely to generate conflict between species protection and human activities."
The researchers also confirmed what others have found: Most endangered species' habitat is on private land. This means creative ways to protect both species and property rights need to be found.
"In particular, we need to supplement the regulatory stick of the Endangered Species Act with some carrots in the form of economic incentives," says Dr. Wilcove of EDF. "We ought to find a way to change the tax code, for example, to reward landowners who affirmatively enhance and restore the habitat of endangered species."
Congress has wrangled over the future of the Endangered Species Act (ESA) for years. Although recovery efforts and other parts of the law continue to be funded, the ESA is several years overdue for reauthorization.
When Republicans took over Congress two years ago, the Senate Republican Regulatory Relief Task Force put it at the top of its "Top Ten Worst-Case Regulations." Since then, efforts to kill or significantly lessen the law have failed in Congress, and the 1996 elections affirmed that most voters favor environmental protection.
Interior Secretary Bruce Babbitt (with the backing of many of the largest environmental organizations) has sought the middle ground in balancing environmental and economic interests in protecting species.
In southern California, for example, state and federal agencies have worked with environmentalists and developers to preserve habitat for a threatened tiny songbird called the gnatcatcher.
"It's not often that environmentalists get all that they're after, and it's not often that developers get all of what they are asking for," says Mr. Roberts.