Yellowstone's whitebark pines, meanwhile, are at risk from a beetle infestation that may be linked to global warming.
The loss of these trees would be dangerous for the park's grizzly bears, which gorge on their large seeds in fall to prepare for hibernation.
The authors warn that unchecked warming could lead to worse consequences for ecosystems and human visitors alike.
If the trend continues, summer visitors to these areas may find bare peaks rather than majestic snowy vistas, and ecosystems will be deprived of precious meltwater.
In addition, warm-weather parks such as Mesa Verde in Arizona and Zion in Utah may become so sweltering that visiting would be a grueling test of endurance.
The unprecedented pace of modern warming, particularly in mountain regions, creates a survival dilemma, conservationists say.
Many plants and animals may not be able to shift their ranges northward in time to survive as the planet warms, they explain. Even if the flora and fauna can make the move, they may have nowhere to go.
"Natural habitats were once contiguous and species moved, but now there are huge gaps," said Stuart Pimm, an environmental scientist at Duke University in Durham, North Carolina, who is unaffiliated with the report.
"National parks are often islands surrounded by extensively human-changed environments, so it's not clear that species will be able to make those kinds of moves."
(Pimm is a member of the National Geographic Society's Committee for Research and Exploration.)
Because they are protected "islands," U.S. national parks may be uniquely able to reveal the impacts of warming that are masked elsewhere, conservationists point out.
"Our national parks have been less impacted by human activities than other lands in the American West," said Bill Wade, chair of the nonprofit conservation group the Coalition of National Park Service Retirees.
"They therefore will serve as indicators of the changing health of our planeta kind of climate-change canary in the coal mine."
Despite the potentially dire consequences of warming, study co-author Theo Spencer of NRDC stresses that the news is not all bad.
"The good news is that there are plenty of solutions to address global warming, and western states are among the leaders in taking those steps," he said.
"Unfortunately our leaders in Washington need to hit the same trail, and they haven't done so."
The U.S. National Park Service declined to comment for this article.
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