TUCSON, Ariz.— A federal judge has ordered the Trump administration to assess what steps are needed to reduce widespread harms some of the nation’s most toxic pesticides are causing to hundreds of endangered plants and animals.

The court’s ruling, released late Wednesday, requires the U.S. Fish and Wildlife Service to conduct legally required biological opinions on the five pesticides’ harms to protected species. The order comes after the Environmental Protection Agency found the pesticides to be harming the majority of the more than 1,800 animals and plants protected by the Endangered Species Act.

“This ruling will force the Trump Fish and Wildlife Service to take action to stop these dangerous pesticides from driving imperiled species like monarch butterflies and California red-legged frogs closer to extinction,” said Jonathan Evans, environmental health legal director at the Center for Biological Diversity. “We’re thrilled to have won this case, but the real victory won’t come until the Trump administration acts on its promise to rein in use of dangerous pesticides like atrazine that are causing grave harms to people and wildlife alike.”

The EPA assessment of the pesticides found that chlorpyrifos is harming 97% of protected species; diazinon, 78%; carbaryl, 91%; atrazine, 56%; and simazine, 55%. In December 2024, while the case was still under the court’s review, the Fish and Wildlife Service completed the biological opinion for a sixth pesticide, methomyl, which the EPA found to be harming 61% of protected species.

Atrazine is the most-used pesticide in the group, with about 70 million pounds of the potent endocrine disruptor used every year in the United States.

Under the first Trump administration, the finalization and release of the Service’s initial analysis of the effects of chlorpyrifos and diazinon on endangered species were blocked by political appointees, as revealed in a New York Times investigation. Yesterday’s court decision requires the Service to complete analyses of the harms to endangered species posed by those two pesticides in addition to the three others.

Under the Endangered Species Act, the Fish and Wildlife Service is required to review the EPA’s findings of the dangers of pesticides’ and put measures in place to prevent species from going extinct or being unnecessarily killed by the chemicals. But the Service has routinely failed to comply, forcing the Center to sue the agency.

The court ordered the Trump Fish and Wildlife Service to complete steps to reduce harm to endangered species by finalizing biological opinions for carbaryl by March 31, 2025; atrazine and simazine by March 31, 2026; and chlorpyrifos and diazinon by Sept. 30, 2028.

“Many of these pesticides are so dangerous they’ve been banned in dozens of other countries, but U.S. officials have lacked the courage and will to stand up to powerful pesticide companies,” said Evans. “We’ll keep holding the Trump administration accountable for obeying our bedrock environmental laws to protect people and wildlife.”

The pesticides at issue are used on a wide array of crops across the country and known to pose substantial threats to human health as well as other animals.’ Chlorpyrifos and carbaryl have been linked to a developmental problems, especially in children, and chlorpyrifos has been banned for food uses in California, Hawai‘i, Maryland, New York and Oregon. Atrazine is linked to a range of hormonal and birth defects and has been banned in Europe for more than a decade.

The ruling was issued in Federal District Court in Tucson, Arizona.