In its latest effort to overhaul the nation’s environmental laws, the Trump administration on Monday disclosed sweeping changes to the Endangered Species Act, a landmark conservation law that over five decades has allowed the federal government to protect imperiled species such as the bald eagle, humpback whale, and whooping crane.

The changes, for the first time, would allow federal officials to assess the economic costs of saving a species, although the law still does not allow costs to be a factor in determining whether to grant a species protection. The new rules also prohibit consideration of the impact of climate change on whether to list a species as endangered. They’re also likely to reduce the number of animal habitats, which are threatened throughout the country by development, critics say.

The move was widely criticized by conservation groups and drew a swift response from Massachusetts Attorney General Maura Healey, who joined her counterpart in California in announcing that they intended to challenge the rules in court.

In a conference call with reporters, Healey and others denounced the new rules as “illegal, arbitrary, and capricious.’’

In a statement, officials from the Department of Interior said the changes to the 45-year-old law would increase its “transparency and effectiveness’’ and “bring the administration of the act into the 21st century.’’

“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,’’ Interior Secretary David Bernhardt said in a statement. “An effectively administered act ensures more resources can go where they will do the most good: on-the-ground conservation.’’

The new rules, which do not require congressional approval, are expected to take effect next month.

The changes come just three months after a United Nations report warned that more than 1 million plants and animals face extinction throughout the world, mainly because of climate change and development. That rate of loss is the highest on record, the report found.

“By gutting key components of the Endangered Species Act, one of our country’s most successful environmental laws, the Trump administration is putting our most imperiled species and our vibrant local tourism and recreation industries at risk,’’ Healey said. “This was illegal, and this is an administration that needs to be held accountable.’’

She and California Attorney General Xavier Becerra said that 99 percent of the species protected by the act have avoided extinction.

“As we face the unprecedented threat of a climate emergency, now is the time to strengthen our planet’s biodiversity, not to destroy it,’’ Becerra said. “By rolling back the Endangered Species Act, the Trump administration would be putting a nail in our coffin — all for the sake of boosting the profits of those putting these species at risk in the first place.’’

Healey credited the act with helping to increase piping plover populations in Massachusetts. When federal officials designated the region’s plovers as threatened in 1986, there were just 139 breeding pairs in Massachusetts. Today, there are nearly 700 pairs.

Vikki Spruill, president of the New England Aquarium, said the act is directly responsible for “restoring whales, seals, and sea turtles to Massachusetts’ coastal waters.’’

“With extinction rates skyrocketing globally and the impacts of climate change on vulnerable wildlife populations unknown, we need a strong, vigorous [Endangered Species Act], not a weaker one,’’ she said.

Other endangered species in the region have not fared as well. North Atlantic right whales, which were hunted nearly to extinction until whaling was banned in the 1930s, now number little more than 400 — down by about 20 percent since 2010.

“Iconic species like the North Atlantic right whale are part of our heritage and deserve all possible protections in the face of the many threats to their continued existence,’’ said Erica Fuller, a senior staff attorney at the Conservation Law Foundation in Boston. “Any attempt to gut one of the public’s most revered statutes, especially in the face of the most recent UN report, demonstrates a lack of respect for both past and future generations.’’

The new rules also make it easier for officials to remove a species from the endangered list and limit protections for those considered threatened.

“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,’’ Secretary of Commerce Wilbur Ross said in a statement. “These changes were subject to a robust, transparent public process, during which we received significant public input that helped us finalize these rules.’’

But conservation advocates said the rules are more likely to weaken protections and ease the way for oil and gas drilling, mining, and other development.

“Our bedrock environmental laws are under assault,’’ said Jamie Rappaport Clark, president of Defenders of Wildlife, a national conservation group based in Washington, D.C. “These rules would change the law in a way that would make it impossible to preserve biodiversity.’’

Others said the new rules would unnecessarily burden the US Fish and Wildlife Service and National Marine Fisheries Service, forcing them to do irrelevant economic analyses.

Factoring in the cost of saving endangered species would likely have prevented other species from being listed in recent years, such as the red knot, a bird that flies through Massachusetts and will soon also be listed as a threatened species, wildlife advocates said.

They called the changes short-sighted, noting the immense value of biodiversity.

“Wildlife conservation provides billions of dollars in economic value to states and communities across the country,’’ said Steve Holmer, vice president of policy for the American Bird Conservancy, a group also based in Washington, D.C. “Birds and other wildlife are an essential part of our natural heritage and play key roles in maintaining healthy ecosystems.’’

►Administration makes it harder for struggling immigrants to get green cards. A2.

David Abel can be reached at dabel@globe.com. Follow him on Twitter @davabel.