Even more than their high-profile polar cousins, Yellowstone grizzly bears could become the newest cause célèbre for how global warming is threatening ecosystems worldwide.

On Nov. 22, a US appellate court ruled for the first time that the federal government must continue to protect an animal – in this case, Yellowstone grizzlies – in part because of the emerging effects of rising temperatures.

For environmentalists arguing that urgent congressional action to combat global warming is needed, the ruling is seen as a benchmark that establishes a legal foothold. It could lower the bar on when the government should take action to try to preserve species threatened by climate changes.

Moreover, the ruling opens the door to charges that federal programs designed to conserve species one at a time – such as the Endangered Species Act (ESA) – could be overwhelmed by a mega-event like climate change, which could affect whole suites of flora and fauna.

"It raises the question of what happens when one species gets in trouble, and its decline pulls the rug out from another species," says attorney Doug Honnold, who helped conservation groups halt the removal of grizzlies from federal protection.

Decline of a key food source

In its ruling, the US Ninth Circuit Court of Appeals said the country's famous Yellowstone bruin population should remain classified as "threatened" under the ESA. The reason: One of its primary food sources is being wiped out, with help from global warming, many scientists say.

Grizzlies gorge on highly nutritious seeds in the cones of whitebark pines. Studies show the nutlike edibles are important in producing healthier, fatter bears and larger numbers of cubs. In addition, because whitebark grow on remote mountain ridgelines, their location draws foraging bears away from places where people live.

However, within the past decade, an outbreak of mountain pine beetles and a disease called blister rust have decimated the whitebark pine forest. Aerial surveys indicate that more than 80 percent of whitebark trees are now dead or dying.

Experts blame warmer temperatures with hastening the spread of beetles that otherwise would be beaten back by cold winters. They say the die-off is unprecedented, prompting an effort to have whitebark itself put on the federal protected list.

The Ninth Circuit's order stays in effect at least until the US Fish and Wildlife Service can figure out a way to deal with the whitebark pine forest's dramatic disappearance.

Indirectly, it also raises questions about similarly threatened species. For example, a tiny alpine rodent, the heat-intolerant pika, is disappearing from mountainous areas in the West. Biologists also worry about impacts of reduced snowpack trends on wolverine, white-tailed ptarmigan, and yellow-bellied marmot.

Yet perhaps the greatest impact of the ruling could be the prospect of the government having to react to the potential cascading effects of global warming. The loss of keystone species, like the whitebark pine, might ripple through the biological food chain. Whitebark seeds nourish not only grizzlies but also Clark's nutcrackers and red squirrels, the latter serving as prey for other species.

Scientists worry that if precipitation patterns are substantially altered in the decades ahead, groups of species could become imperiled, with the loss of one triggering declines in others.

Significantly, the judges acknowledged "a general consensus among the world's best scientists that climate change is occurring" and added, "the magnitude of warming in the northern Rocky Mountains has been particularly great."

In some ways, the court ruling clashes with a prevailing public perception that Yellowstone grizzlies no longer need the ESA. Since the Yellowstone bear population came under federal custodial status in 1975, numbers have tripled to about 600.

Government officials say the ruling ignores the fact that there are plenty of other natural foods for grizzlies to eat. Whitebark pine has all but vanished from Glacier National Park because of a disease outbreak 60 years ago, yet the bear population there today is a robust 900.

Biologist Chris Servheen, the US Fish and Wildlife Service's longtime coordinator of grizzly bear recovery, believes conservation groups are using whitebark to hold up delisting, and he worries it could incite a backlash against the ESA.

"This court ruling will further erode public support for sound grizzly conservation among the people who are most important to their survival – those who live, work, and recreate in bear habitat and the political forces who are responsive to these people," he says.

A new urgency

In the late 1990s, Mr. Servheen and colleagues began building the case to hand management of grizzlies over to Wyoming, Montana, and Idaho. He says federal agencies beset by limited budgets should try to bolster less-healthy grizzly populations in areas such as the Cabinet-Yaak ecosystem along the Montana-Canada border and the northern Cascades.

But by having the court recognize the connection between grizzlies and whitebark pine, advocates pushing for action on climate-change policy may have found a potent symbol for their cause.

Polar bears have received "threatened" status based upon the strong likelihood that Arctic ice will disappear, hobbling their ability to hunt. But the Nov. 22 court ruling points to climate-related impacts in the here and now, not looming in the future, Mr. Honnold says.