About 700 grizzly bears that roam the Yellowstone National Park area will soon lose the protections they have had under the Endangered Species Act for more than 40 years, the Interior Department announced Thursday.

The change, which is set to take effect next month, is a sign of the major comeback by the Yellowstone bears. An icon of the American West, their numbers were driven to as low as 136 before the Yellowstone population and others in the Lower 48 states were listed in 1975. Interior Secretary Ryan Zinke said in a statement that the grizzlies’ recovery is “one of America’s great conservation successes, the culmination of decades of hard work.”

But the delisting decision is also highly controversial and almost certain to be challenged in court by conservation organizations that still view the bears as vulnerable to both human and environmental threats. While those inside Yellowstone and nearby Grand Teton National Park will remain protected, wildlife officials in the surrounding states — Montana, Idaho and Wyoming — will now manage grizzlies that stray outside. That will permit the states to allow hunting, provided the regional grizzly population stays above 600 over the next five years, as well as the killing of bears that harm livestock in a ranching-heavy area.

As many as 50,000 grizzly bears once inhabited the lower United States, but centuries of hunting and extermination left the bears on what is now less than 2 percent of their original territory. Another group of about 1,000 grizzlies lives in northern Idaho and Montana, near Glacier National Park, and a very small number is in the Northern Cascades in Washington. Those bears will remain protected.

The delisting of the Yellowstone population comes more than a year after the Obama administration first proposed it, setting off an extensive review of the states’ management plans. More than 650,000 public comments on the issue were submitted to the U.S. Fish and Wildlife Service, a volume that helped delay a decision that officials hoped to have made by the end of 2016.

Critics cite several concerns about the move, including a decline in the white bark pine that grizzlies eat; that argument prompted a federal court to rule against an initial delisting in 2007. Conservation groups also argue that the Yellowstone grizzlies are an isolated group and that their routes to other bears in the region must be protected if they are to maintain genetic diversity.

“If trophy hunting commences outside of Yellowstone and Grand Teton, the very bears critical to establishing connectivity with other isolated populations will be the first to die,” said a statement issued by Matthew Bishop of the Western Environmental Law Center and Kelly Nokes of WildEarth Guardians, which said it would challenge the decision. The Endangered Species Act, they continued, “is not designed to make our National Parks into proverbial zoos, where only small, isolated subpopulations of species exist.”

At least 123 Native American tribes, for whom grizzlies have cultural and spiritual significance, have signed a treaty opposing the removal of grizzly protections, saying federal officials did not take their views into account.

“The Fish & Wildlife Service promised us that it would conduct full and meaningful consultation with us, but it turns out, those were only empty promises,” said Ben Nuvamsa, the former chairman of the Hopi tribe, whose members view the grizzly as a “medicine man or a medicine bear” with the power to heal. Nuvamsa’s comments were circulated by Rep. Raul M. Grijalva, D-Arizona, who said he would introduce legislation to protect all grizzly bears, listed or not.

Some officials in Idaho, Wyoming and Montana said Thursday that they welcomed the news. “Grizzly bears have met or exceeded recovery objectives since 2003 and have long warranted delisting,” Wyoming Gov. Matt Mead said. “Thanks to the team effort, grizzlies will be managed appropriately by our experts at Game and Fish.”

Even some observers who argue that the bears have indeed recovered from the brink of extinction have expressed concern about how the states will manage what is known as “discretionary mortality,” or the willful killing of bears by hunting or to deal with “problem bears.” Yellowstone Superintendent Dan Wenk, for example, has said that while he believes the bears are ready to be removed from the Endangered Species list, he worries that too many bear deaths could affect the experience of the thousands of park visitors who come to see grizzlies.

Chris Servheen, who retired last year after serving as Fish and Wildlife’s grizzly bear recovery coordinator for 35 years, said in an interview this year that the bears were ready for delisting. Grizzly diets are diverse enough to deal with the decline in white bark pine, and well-managed hunting would not pose a major threat, he said.

“Where we are now is where we need to stay,” he said. “But a managed population decline post-delisting is not biologically defensible. We didn’t recover them to drive the population down.”