The Trump administration announced a major overhaul Monday to the Endangered Species Act that it said would reduce regulations. Environmentalists said the changes would push more animals and plants to extinction because of threats from climate change and human activities.

The changes end blanket protections for animals newly deemed threatened and allow federal authorities for the first time to take into account the economic cost of protecting a particular species.

The Endangered Species Act protects more than 1,600 species in the USA and its territories.

“The best way to uphold the Endangered Species Act is to do everything we can to ensure it remains effective in achieving its ultimate goal – recovery of our rarest species,” U.S. Secretary of the Interior David Bernhardt said in a statement. “The act’s effectiveness rests on clear, consistent and efficient implementation.”

U.S. Secretary of Commerce Wilbur Ross said, “The revisions finalized with this rulemaking fit squarely within the president’s mandate of easing the regulatory burden on the American public, without sacrificing our species’ protection and recovery goals."

The act helped save the bald eagle, California condor, the grizzly bear and dozens of other animals and plants from extinction since President Richard Nixon signed it into law in 1973.

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At least 10 attorneys general joined conservation groups in protesting an early draft of the changes, saying they would put more wildlife at greater risk of extinction.

“These changes crash a bulldozer through the Endangered Species Act’s lifesaving protections for America’s most vulnerable wildlife,” said Noah Greenwald, endangered species director at the Center for Biological Diversity. “For animals like wolverines and monarch butterflies, this could be the beginning of the end.

"We’ll fight the Trump administration in court to block this rewrite, which only serves the oil industry and other polluters who see endangered species as pesky inconveniences,” he said. “We’ll do everything in our power to get these dangerous regulations rescinded, including going to court.”

Drew Caputo of the environmental group Earthjustice said, "This effort to gut protections for endangered and threatened species has the same two features of most Trump administration actions: It's a gift to industry, and it's illegal. We'll see the Trump administration in court.”

The Endangered Species Act has prevented more than 99% of listed species from going extinct, according to Earthjustice. It is also wildly popular: 90% of Americans support the act, the group said.

Late Monday, both California and Massachusetts said they’ll go to court to fight the Trump administration’s overhaul of the act.

U.S. Fish and Wildlife Service official Margaret Everson said during a media call Monday that the changes “provide the maximum degree of regulatory certainty” while protecting species.

The Property and Environment Research Center praised the changes. "Our interest is getting this landmark wildlife protection law to work better,” Executive Director Brian Yablonski said. “That means fostering conditions so landowners become more enthusiastic in their role as stewards for species recovery, not worried if they find an endangered species on their land.”

A United Nations report warned in May that more species – as many as 1 million plants and animals – are threatened with extinction now than at any other time in human history because of development, climate warming and other threats.

Contributing: The Associated Press