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The DNA of extinction

September 15, 2006|Sylvia Fallon and Andrew Wetzler | SYLVIA FALLON is a conservation genetics fellow and ANDREW WETZLER is director of endangered species projects for the Natural Resources Defense Council.

THE PASSENGER pigeon -- a dove with bluish wings and a wine-red breast -- was once probably the Earth's most numerous bird. On Sept. 14, 1914, at about 1 p.m., the last passenger pigeon died at the Cincinnati Zoo. Her name was Martha, and though she belonged to a species once so abundant that its flocks were more than a mile wide and more than 300 miles in length, she died alone.

Scientists know of at least 16,000 animals and plants that are in danger of extinction. Traditional threats such as over-hunting, which wiped out the passenger pigeon, are now joined by modern dangers such as habitat destruction, "invasive" species, pollution and the specter of global warming. The number of species classified as threatened with extinction by the International Union for the Conservation of Nature has jumped by 60% in the last decade alone.

But today, the U.S. Endangered Species Act -- our nation's safety net for species on the brink of extinction -- is open to manipulation because of the rising influence of a new, and often misunderstood, field of science: conservation genetics. Improperly analyzed genetic data have been used to claim that there are fewer populations of endangered species than we thought, and therefore fewer that need protecting.

One of the fundamental provisions of the Endangered Species Act is its authority to protect not just entire species threatened with worldwide extinction but also subspecies and distinct populations. Without this provision we would not have been able to protect the bald eagle, the gray wolf, the grizzly bear and other species that were endangered in the lower 48 states but had healthy populations in Canada and Alaska. Because distinct populations of these animals were on the verge of extinction, they qualified for the special protection that has brought them back with remarkable success.

That might not happen today.

Technical and theoretical advances in the field of genetics -- unknown to the authors of the law -- have exploded over the last decade, and now genetic information is increasingly being used to determine which populations deserve protection under the Endangered Species Act and which do not. Scientists chart the differences and similarities among groups of organisms through their genetic makeup, which is represented in an alphabet-like code. Some of the letters in this code are passed on virtually intact from parents to their offspring generation after generation. By examining this code, scientists can tell how closely related different species, subspecies and even populations of animals and plants are to each other.

But there are no federal guidelines on how much genetic data should be used to determine what is a distinct population of animals. And the problem is, if you don't look at enough information, you might not see differences among populations.

Recently, the Natural Resources Defense Council systematically reviewed 10 years of decisions, based on genetic studies, about whether to protect individual wildlife populations under the Endangered Species Act. We found that when geneticists analyzed large amounts of data, the outcome proved the animal was part of a distinct population 80% of the time. But when they looked at less data, the animal was deemed deserving of protection only 30% of the time. These results show that the lack of a guideline for genetic analysis is putting populations of animals at risk of extinction.

A recent case in Colorado pitted two genetic studies against each other over a threatened meadow jumping mouse, which gets its name from its remarkable ability to leap 18 inches in the air. Its habitat has been dwindling because of development. The original study, promoted by developers, used minimal genetic evidence to argue for taking this mouse off the endangered species list. However, a follow-up study used a better, larger set of data and found a clear need for continued protection. The mouse's fate still hangs in the balance.

Luckier are the southern resident killer whales that visit Washington state's Puget Sound every summer. Some were lost in the 1970s to Shamu-style aquarium displays, and the small population declined further in the 1990s because of pollution and noise from vessel traffic. But the whales are now protected because a larger, more informative genetic analysis showed they are a distinct population.

The Endangered Species Act already requires the Fish and Wildlife Service to consider the "best available science" to determine which wildlife populations are worthy of protection. That standard should not allow insufficient information to determine which populations of animals live or die.

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