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Environmental economist Erik Nelson recently studied the impact of U.S. Endangered Species Act regulations on habitats considered most vital to the persistence of endangered and threatened species. With his research collaborators, Nelson found that the regulations have had no discernible effect on how people are using these protected lands. 

Passed into law in 1973, the U.S. Endangered Species Act has had more than four decades to make a difference in the survival of imperiled wildlife and plants. But it’s debatable whether the law is working well.

To evaluate a portion of the law’s legacy on lands designated as critical habitat, Assistant Professor of Economics Erik Nelson collaborated this year with three scientists who specialize in ecology and conservation biology. Their research project is a timely undertaking, as the White House, U.S. policy makers, and nongovernmental organizations are increasingly looking for evidence on which environmental regulations are working as intended and which ones are not.

With a grant from a think tank called , Nelson and his co-authors — John Withey of Florida International University, Derric Pennington of the World Wildlife Fund, and Joshua Lawler ’93 of the University of Washington — looked into what is happening to the critical habitats the Endangered Species Act is designed to protect. When an animal or plant becomes listed as endangered or threatened, a recovery plan is drawn up and the habitats needed for its long-term success are also meant to be identified and protected. 

In their paper, the researchers argue that despite the law’s intention to limit activities in critical habitats, it has not had a tangible effect. Nelson said he had expected to find that critical habitats would look different from nearby areas that lay outside the protected zones. For instance, he thought development might be less intensive and conservation of forest and wetlands might be more prevalent in critical zones.

But, Nelson explained, “We didn’t see any difference in land-use conversion,” for either developed land in urban and residential areas or for agricultural land. “An effective conservation program would promote the maintenance of critical habitats,” he added.

Most critical habitats are on private land, and some critics of the Endangered Species Act have said landowners face considerable economic consequences when income-generating activities on their land are restricted. Landowners are expected to comply with the law by not pursuing actions, such as road building or switching from pastureland to cropland, that might further jeopardize an endangered species.

Nelson speculated that the lack of species-friendly land-use changes in critical habitats could be due to political obstacles that the U.S. Fish and Wildlife Service faces in enforcing the Endangered Species Act. Another possible explanation of the law’s limited impact is that many critical habitats might have been established in areas that aren’t economically useful to people.

In addition, the researchers had anticipated seeing more land trusts and conservation agencies acquiring sensitive ecosystems. Critical habitats “should attract an extraordinary amount of attention from conservation organizations,” they write in their paper. But this is not the case. Nelson theorized that conservation groups might not be buying critical habitats because they are opportunistic rather than strategic, and they make deals with the landowners who offer to sell to them. Or perhaps landowners ask higher prices when they know the value of their critical habitat to conservationists. “Conservation organizations may be less active in critical habitats with higher land values because of limited budgets for land conservation,” he writes in the paper.

Nelson’s research will contribute to an ongoing debate about the viability of the Endangered Species Act. “There have been some success stories, but not many,” he said. While very few of the 2,200 or so listed species have slipped into extinction, only 28 have survived sufficiently to be delisted.

However, he argued, this does not mean the Endangered Species Act overall has been a waste. “What would have happened without the Endangered Species Act?,” Nelson posed. “It could be that many endangered species that are still with us would be extinct.”