50 Years: How the Endangered Species Act Influenced Greater Yellowstone

Imagine Yellowstone National Park without iconic wildlife like grizzly bears, gray wolves, bald eagles or bison. Fifty years ago, that was the trajectory of the park—and the rest of the Lower 48.

When the Endangered Species Act was enacted on December 28, 1973, grizzlies had been eliminated from 98 percent of their historic range in the contiguous U.S., no wolf packs lived in Yellowstone, and just a few hundred bald eagles remained south of the Canadian border. Now, each of these species has thriving populations across Greater Yellowstone.

The Endangered Species Act passed with bipartisan support to establish federal protections for declining species of fish, wildlife and plants. The act was designed with the dual purpose of protecting animals and conserving the ecosystems they rely on, according to the U.S. Department of the Interior.

The ESA, most recently amended in 2003, was the end-result of various attempts at wildlife conservation. Among the law’s precursors was the Lacey Act of 1894, a law intended to specifically protect Yellowstone National Park’s wildlife and plants from illegal harvest, that was later enacted nationwide.

The Endangered Species Preservation Act of 1966 and Endangered Species Conservation Act of 1969 heralded the need for a more broad-reaching piece of legislation, thus setting the stage for the ESA.

According to the Center for Biological Diversity, the ESA has a 99 percent success rate in protecting its listed species from extinction, and currently extends protections across more than 1,600 species. Among the act’s success stories are a trio of iconic animals that form the Greater Yellowstone Ecosystem we know today.

Grizzlies have been listed under the ESA in the Lower 48 since 1975. Prior to European settlement in the 1800s, an estimated 50,000 grizzly bears were widely distributed across the West. The bruins posed threats to livestock and human expansion, and, per government-funded bounty programs, were killed wherever they were found, reads to the species’ ESA listing page. By the time of their listing, just 700-800 grizzlies remained in the contiguous U.S. where they were largely confined to federal lands in Washington, Idaho, Montana and Wyoming.

A grizzly bear recovery program was approved in 1993 outlining recovery efforts across six zones, including the Greater Yellowstone Ecosystem. Population numbers now hover around 2,000 individuals, according to a 2022 Fish and Wildlife Service population report, and bears are reinhabiting areas they haven’t existed in for more than a century.

Following a successful recovery, grizzlies in the Northern Continental Divide and Greater Yellowstone ecosystems now face potential delisting from the ESA, which would transfer management from federal to state agencies. In February 2023, the Fish and Wildlife Service released findings prompted by three petitions to delist the bruins, suggesting substantial evidence for delisting in NCDE and GYE. The Service is currently preparing a status review for grizzly bears in these two ecosystems to determine their future listing status.

An adaptive species whose range once spanned two-thirds of all U.S. states, the gray wolf was added to the endangered species list in 1978. Much like grizzlies, the predators were nearly eradicated as settlers expanded west. By the 1970s, extensive research found no evidence of wolves established inside Yellowstone National Park. Following the species’ listing, Congress established plans to reintroduce wolves to Yellowstone and from 1995-1997, a total of 41 wolves from Canada and northwestern Montana were relocated into the park.

The wolves quickly and successfully established a population in the region and as of January 2023, Yellowstone documented at least 108 wolves distributed between 10 packs inside the park. Currently, wolves are no longer listed in Idaho, Montana and Wyoming, although they remain listed in other states.

As many as 100,000 bald eagles nested in the Lower 48 prior to European settlement. The bald eagle has been the national bird of the United States since 1782, though it faced near extinction in the contiguous U.S. by the mid-1900s due to shooting, food contamination and habitat loss. By 1963, the U.S. Fish and Wildlife Service reported just 417 nesting pairs.

Federal agencies tried multiple times to protect the bald eagle, including through legislation in 1940 and 1967. But it wasn’t until the 1972 banning of dichlorodiphenyltrichloroethane, a harmful insecticide commonly known as DDT, along with the species’ ESA listing in 1978, that populations truly started to rebound. Through captive breeding programs, habitat restoration and nest-site protection, bald eagles were delisted in 2007. In a 2020 population study, the Fish and Wildlife Service estimated 316,700 individuals in the Lower 48. Eagles in Yellowstone are part of the Rocky Mountain breeding population which extends into Montana and Idaho, and in 2022 the National Park Service reported 28 bald eagle territories inside Yellowstone National Park.

Tens of millions of bison once roamed the continent, and the iconic mammals were crucial to indigenous tribes. As settlers moved West during the 1800s, the U.S. Army began forcibly removing Native Americans from their ancestral lands and, as a part of such campaigns, hundreds of thousands of bison were killed by U.S. troops and market hunters throughout the century. By 1880, just a few dozen bison remained in Yellowstone, according to the Park Service.