Joshua Tree National Park in the Southern California desert could lose almost all its joshua trees. An adorable alpine mammal, the American pika, might disappear from its favorite roosts, like the high country of Lassen Volcanic National Park. Montana's Glacier National Park could even find itself glacier-less.

These and other severe outcomes are projected to be coming to America's 417 national parks, monuments and preserves, if the worst impacts of climate change are not staved off by massive reductions in greenhouse gases, according a new study from researchers at the University of California, Berkeley and the University of Wisconsin.

The environmental scientists looked at historic temperature increases from 1895, into the 21st century and then projected temperature hikes through the year 2100. They did the same for rainfall totals over all of the 50 states.

The review found that recorded temperature increases in the protected zones was twice as high, from 1895 to 2010, as temperature increases in the the rest of the United States. And those greater temperature increases would be exacerbated through the end of the century, if the United States and the world do nothing to reduce the level of carbon dioxide and other heat-trapping gases, the researchers found.

The study essentially concludes that areas that are chock-full of national parks — places like Alaska and the American Southwest that have already seen dramatic temperature hikes leading to retreating ice, melting permafrost, prolonged droughts and increased wildfires — will be the scene of the greatest heat gains, and rainfall declines, in the future.

Using previous data that they aggregated and reassessed, the researchers concluded that under the worst-case scenario, no reduction in earth-warming greenhouse gases, temperatures would increase between 5.4 degrees Fahrenheit and 16.2 degrees Fahrenheit. The most severe increases would hit Alaska's North Slope, where grizzly bears, caribou, polar bears and other sensitive species make their homes.

"The findings are consistent with what people think about those areas. But, before our research, the severity of climate change across all national parks was unknown," said Patrick Gonzalez, a professor of environmental science at UC Berkeley and a lead author of the study. "The surprising result is the magnitude of the difference; that national parks are exposed to temperature increases and conditions that are double the national increases. That is a major difference."

While climate change skeptics might try to argue about forward-looking worst-case scenarios, the authors of "Disproportionate Magnitude of Climate Change in United States National Parks" noted that many severe impacts already have been seen.

Even with strong greenhouse gas controls like those envisioned by the Paris climate accord, which President Donald Trump pledged to abandon, the average temperature in national parks is projected to increase 2 degrees Celsius.

In Alaska's Glacier Bay National Park, north of Juneau, the majestic Muir Glacier has retreated about 31 miles from its one-time ocean-front terminus on Muir Inlet. Photos from the 19th century show a towering white ice face, where present-day photos reveal only open water.

In the nation's original national park, Yellowstone, a bark beetle infestation has wiped out more than one million acres of whitebark pine trees. That creates a cascading set of problems, including the invasion of bears in lower elevations, where they come into more frequent conflict with humans.

The forward looking projections in the Berkeley/Wisconsin research are even more drastic. Jack Williams, a report co-author who is a geography professor at the University of Wisconsin, said its now not unreasonable to think of a time when an iconic national park will lose its namesakes.

"At this point, I think it's likely that the glaciers in Glacier National park will ultimately disappear, and what is [Montana's] Glacier National Park if it doesn't have glaciers anymore?" Williams said.

In Joshua Tree National Monument southeast of Los Angeles, as many as 90% of the park's prickly namesakes could be wiped out by 2100, if temperatures continued to spiral upward, uncontrolled, the report projects.

The pika, a guinea pig-like creature adapted to rocky mountaintops is so temperature sensitive that it will be one of the first mammals to see its habitat constrained, the researchers said. It would probably be driven entirely from Lassen, the Northern California national park, under the expected conditions, should humanity fail to bring greenhouse gases under control, the study said.

The best hope for reducing the impacts would be for governments, companies and individuals to help the U.S. and other nations get carbon dioxide and its sister contaminants under control, the report's authors said.

Other stopgap measures are already being put in place by the National Park Service, which helped pay for the research. The agency is trying to designate refuge areas in each of the parks where measures can be taken to help protect plants and wildlife.

At Joshua Tree, for example, park service managers are closely monitoring trees to see which are most vulnerable to excess heat and lack of rainfall. In areas designated as refuges, the service is taking extra measures to keep out the invasive grasses that spread destructive wildfires and deploying extra fire protection crews when fires do break out, Gonzalez said.

In California's Yosemite National Park, the areas most in danger from heat and drought-driven fire are being mapped and subject to controlled burns. The hope is that by reducing fuels in the short term that the long-term risks from fire will be reduced.