Just before Inauguration Day, the Environmental Protection Agency (EPA) released a long-awaited report: the final biological evaluations for how three widely used pesticides impact threatened and endangered species. The agency found that all three—chlorpyrifos, diazinon, and malathion—may adversely affect virtually all species listed under the Endangered Species Act (ESA).

In fact, when it comes to birds, the EPA found that only five listed species would not be affected—one that exists only in captivity and four that remain on the list but are presumed extinct in the U.S.

Such a conclusion would seem actionable. But documents obtained last week by the Associated Press revealed that Dow AgroSciences and two other pesticide manufacturers asked the EPA to ignore those findings—based on several years and 10,000 pages of research—saying the results are “flawed” and shouldn’t be used to set policy.

“That was disturbing news to say the least,” says Cynthia Palmer, American Bird Conservancy’s director of pesticides science and regulation. “Birds are among the most sensitive vertebrates to organophosphate pesticides, and particularly to chlorpyrifos.”

The three pesticides evaluated by the EPA all belong to a class of chemicals called organophosphates, which interfere with the nervous system’s ability to send signals. This makes them very effective at killing target insects. Unfortunately, the pesticides can travel via air and water, harming other organisms that come into contact with them. Studies have shown that organophosphates can cause muscle failure and breathing and reproductive problems in birds. They can also impair birds’ ability to fly and eat, leaving them exhausted and vulnerable to predators, and can disorient them during migration.

Exposure to chlorpyrifos and diazinon, which ranges from walking on treated vegetation to ingesting contaminated insects or seeds, can also kill birds outright, says Pierre Mineau, a biologist at Carleton University whose research focuses on pesticide impacts to birds. Malathion, says Mineau, is also toxic to birds but has less dramatic direct impacts.

Of the 108 ESA-listed bird species, the EPA found chlorpyrifos may adversely affect 103 and is “likely” to adversely affect 91. The numbers were the same for malathion and only slightly lower for diazinon. Impacted species include the Whooping Crane, Piping Plover, Greater Prairie-Chicken, Tricolored Blackbird, and Kirtland’s Warbler. But the list also includes hawks, ducks, geese, swans, hummingbirds, herons, gulls, sandpipers, egrets, doves, cranes, kingfishers, pheasants, woodpeckers, parrots, owls, falcons, and condors.

“We’re particularly concerned about birds that have been making a comeback,” Palmer says. “It would be crazy to reverse all that progress.”

Kirtland's Warbler. Eric Fishel/Audubon Photography Awards

The three pesticides have been used since the 1950s and ‘60s, but based on growing evidence of toxicity—including studies that show chlorpyrifos can impair children’s neurological development—the EPA has restricted some applications over the past 10 to 20 years. Since 2000, the EPA has banned chlorpyrifos and diazinon from most indoor residential uses. It has also banned chlorpyrifos’ use on tomatoes and limited its use on apples, grapes, citrus, and other crops. In 2015, the EPA proposed banning the application of chlorpyrifos on all food crops—a decision that EPA Administrator Scott Pruitt reversed in March. Mineau called this move “a step backwards.”

Environmental-impact studies compiled by the EPA show that the agency has known about the pesticides’ toxicity to birds since the 1970s. But it only formally investigated their possible risk to endangered species as part of a 2014 legal settlement with the Center for Biological Diversity (CBD), which had sued the EPA for failing to comply with the ESA—claiming the agency had essentially turned a blind eye to pesticides’ effect on wildlife.

Lori Ann Burd, CBD staff attorney and environmental health program director, notes that the EPA’s biological evaluations only consider the effects of individual pesticide exposures—not those of exposure to multiple pesticides, perhaps more of a reality for birds. Even so, “the abundance of the science makes it impossible to ignore the conclusions,” she says.

Of course, that’s exactly what pesticide manufacturers are asking the EPA to do. (Federal disclosure forms show that Dow has already spent $5.2 million lobbying the federal government in 2017, including on pesticides and the ESA.) And if the agency complies, impacts to endangered species will be disregarded while chlorpyrifos continues to be used on corn, soybeans, and numerous fruit, nut, and vegetables crops; malathion on vegetables and fruit and to control mosquitos, including to curtail the Zika virus; and diazinon on almond and fruit orchards and on vegetables such as lettuce and tomatoes.

The U.S. Fish and Wildlife Service and National Marine Fisheries Service, which share enforcement of the Endangered Species Act with the EPA, have also been compelled by legal settlements with CBD to release biological opinions of the pesticides’ impacts on endangered species. Drafts of those are due by the end of 2017. There’s hope that these will trigger further action. But as Mineau notes, “To see all of this being put back into play is regressive beyond belief.”

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