Disappearing glaciers were an early sign of trouble for the nation’s wildlands.

But the mark of global warming on the American landscape didn’t end there. Devastating wildfires have since ravaged Yosemite. Rising seas have encroached on the Point Reyes Peninsula. Vast stands of trees have died in and around Kings Canyon.

A study released Monday finds that the country’s national parks, which were designed to set aside and protect the most pristine and coveted spots in the United States, are being hit disproportionately by climate change.

Temperatures across 417 sites managed by the National Park Service, from the Florida Everglades to Yellowstone to Alaska’s Mount Denali, have increased at twice the rate as the rest of the country, the study finds. The parks also have experienced greater declines in rainfall.

Such hotter, drier conditions are expected to persist in many of the parks, probably magnifying the harm that’s already begun to afflict mountains, forests and the coast as well as the plants and animals that live there.

The Trump administration’s unraveling of global warming policies and the National Park Service’s backsliding on climate programs under President Trump stand only to exacerbate the risk.

“Up until our research, the severity of climate change across the national parks was unknown,” said Patrick Gonzalez, a climate change scientist at UC Berkeley and lead author of the study. “Human-caused climate change exposes the national parks more severely than the rest of the United States.”

The reason for the disproportionate hit is relatively simple. National parks encompass the country’s most extreme environments where warming has generally been greater, the study notes. Many parks are at high elevations where the atmosphere is thinner and in the Arctic where the reflective snow cover has melted and more heat is being absorbed.

While the research, by scientists at UC Berkeley and the University of Wisconsin, does not detail the specific problems that national parks are facing, the study offers a first-of-its-kind analysis of the temperature and precipitation changes that are driving many of the problems. The findings are published in the journal Environmental Research Letters.

According to the study, temperatures across the national park system have increased a little more than 1 degree Celsius, or 1.8 degrees Fahrenheit, between 1895 and 2010, about double the country’s average. While the increase may seem modest, scientists have warned that warming of more than 2 degrees Celsius is a threshold that comes with grave risk.

In California, 23 out of 27 park sites, including Golden Gate National Recreation Area, Death Valley and Joshua Tree, have seen temperatures rise since 1950, sometimes far more than 1 degree Celsius.

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Rainfall changes in the parks have been more variable. While in most parts of the country, annual precipitation has increased from 1895 to 2010, rain totals decreased across 12 percent of parklands, according to the research. By comparison, just 3 percent of all U.S. lands has seen a decline.

Going forward, the researchers project the average temperature across national parks will rise about 5 to 7 degrees Celsius, or 9 to 13 degrees Fahrenheit, by 2100, roughly a half degree more than the rest of the country, under the study’s most extreme modeling scenario. If heat-trapping emissions are capped as called for in the Paris climate agreement, average temperature increases will be limited to about 1 to 3 degrees Celsius, or roughly 2 to 6 degrees Fahrenheit.

Regardless of which scenario plays out, according to the study, parks in Alaska are expected to see the most warming.

While the study’s precipitation models show wide variation in future rainfall, parks in Hawaii, the Virgin Islands and the American Southwest are projected to see the biggest declines.

Changes in temperature and rainfall, though, will probably have implications for most parks, in many cases well beyond what’s already occurring.

In Yosemite, earlier research shows that forests as well as small mammals have begun shifting upslope to cooler areas as temperatures have risen, threatening wholesale disruption if the warming continues.

In Joshua Tree, the park’s namesake tree is struggling amid intensifying heat, and researchers worry that much of the park could become unlivable for the tree if the trend persists.

In Point Reyes, oceans are washing farther up beaches as sea levels rise and the habitat of elephant seals may one day be at risk.

The National Park Service has long studied the impacts of climate change, with both federal scientists and independent researchers, and a commitment to conserving wildlands amid rising temperatures remains part of the agency’s mission.

But Jonathan Jarvis, former director of the Park Service and now executive director of UC Berkeley’s Institute for Parks, People and Biodiversity, said those in the Trump administration currently running the agency aren’t making climate change a priority.

“What concerns me is there’s no clear leadership on the issue,” said Jarvis, who recently wrote a book, “The Future of Conservation in America: A Chart for Rough Water,” on the challenges facing public lands.

“The Park Service in the past has played a leadership role … and all of that is sort of lost at the moment,” he said.

Jarvis said park leaders during his tenure had begun to look beyond park borders at nationwide climate adaptation strategies, such as creating large-scale wildlife corridors for animals to move to more hospitable places. But those far-reaching efforts, he said, have ceased under Trump.

The National Park Service did not respond to requests for comment before this story was published. Officials at Yosemite National Park also did not comment.

At many parks, research and action on climate change continue despite a change in priorities in Washington.

In Sequoia and Kings Canyon, scientists are looking into ways to make sure the giant sequoias endure amid a hotter, drier future. In other parks, researchers are looking to restore the shade provided by forests so rivers are cool enough for fish to survive. Elsewhere, wetlands are being restored to protect against sea level rise.

John Dell’Osso, chief of interpretation and resource education at Point Reyes National Seashore, said the Marin County park is constantly being monitored to make sure wildlife, from marine mammals to seabirds, adapt to climate change.

“We’re contemplating many what-if scenarios,” he said. “We’re kind of looking at everything.”

Kurtis Alexander is a San Francisco Chronicle staff writer. Email: kalexander@sfchronicle.com Twitter: @kurtisalexander