Despite being protected lands, it appears that America's national parks aren't safe from the effects of a changing planet.

Man-made climate change is exposing even our most iconic national parks — think Joshua Tree, Glacier Bay and Yosemite — to weather that's hotter and drier than the national average. This is causing changes in vegetation, melting glaciers and wildfires, according to a study published in Environmental Research Letters.

"National parks aren't a random sample — they are remarkable places and many happen to be in extreme environments," Patrick Gonzalez, an associate adjunct professor in the environmental science and policy at University of California, Berkeley, and lead author of the study, said in a statement released by Berkeley. "Many are in places that are inherently more exposed to human-caused climate change."

Hotter and drier

Weather stations have tracked monthly temperatures and rainfall of the national parks since 1895. Gonzalez and his team used this data and created maps to track the change in average temperature and precipitation between 1895 and 2010. They then mapped future changes to the parks using climate change models developed by the Intergovernmental Panel on Climate Change (IPCC) in 2013.

Researchers found that temperatures increased in the national parks by a little over 1 degree Celsius over the historical range. This was double the change experienced by the rest of the country over the same time span. Denali National Preserve in Alaska was hit the hardest with hotter conditions, its average temperature increasing by 4.3 C over the 115-year period.

Meanwhile, precipitation fell dramatically for the parks, a whopping 12 percent between 1895 and 2010, four times the U.S. average. Parks in Hawaii, Alaska and the southwestern U.S. saw considerable decreases, with Hawaii's Honouliuli National Monument experiencing an 85 percent drop in precipitation.

Fog and frost cover a range of Denali National Park Denali National Park and Preserve experienced significant increases in temperatures between 1895 and 2010. (Photo: Tim Rains/National Park Service/Wikimedia Commons)

The effects of these changes can be see and felt readily in these parks, according to Gonzalez.

"These impacts include melting of glaciers in Glacier Bay National Park, Alaska, tree death from bark beetles in Yellowstone National Park, upslope vegetation shifts in Yosemite National Park, California, and northward vegetation shifts in Noatak National Preserve, Alaska," he writes in a post for The Conversation.

When mapping future changes, the researchers applied what they call "storylines for the future," each one representing a different climate model. One involves no action to reduce greenhouse gases, a second involves reductions made in line with the Paris climate accords and the third and fourth models fall somewhere between the other two models.

Under the most extreme model in which nothing is done to reduce current greenhouse gas emissions, temperatures across the 417 park units would increase between 5 and 7 C on average by 2100. Following the Paris accords would result in a 1 to 3 C temperature increase. Alaska would bear the brunt of these temperature increases, regardless of which model is followed. For instance, parks in Alaska experienced temperatures 9 C higher by 2100 under the no-reductions model.

"In places where models project high temperature increases, research has found high vulnerabilities of ecosystems," Gonzalez writes in The Conversation. "These vulnerabilities include severely increased wildfire in Yellowstone National Park, extensive death of Joshua trees in Joshua Tree National Park, California and possible disappearance of American pika, a small alpine mammal, from Lassen Volcanic National Park, California."

Precipitation under these models would not change as dramatically as the temperature would, however. "The ranges of almost all the projections of annual precipitation overlap the range of annual precipitation in the historical period, suggesting no significant projections of change at a large scale," the researcher conclude. Virgin Islands National Park was the only park to experience significant reductions in precipitation, some 28 percent by 2100.

Saving the parks

Scientists measure the edges of Glacier National Park's Grinell Glacier in 2008. Scientists measure the edges of Glacier National Park's Grinell Glacier in 2008. (Photo: Glacier National Park/Wikimedia Commons)

Researchers also "downscaled" their models to create detailed projections within an individual park. The goal of these projections is to help the National Park Service (NPS) prepare for and protect against these changes, including switching to different energy sources and developing measures to combat invasive species.

Whether or not the NPS can act on these findings is a matter of politics. As The Guardian reports, the Department of the Interior has nixed a policy that encouraged the NPS to make resource-management decisions based on science, including any climate change research.

Even while many of the parks are in extreme locations, and thus more vulnerable to changes in climate, their decline is a warning to all of us about the loss of natural lands and our own well-being under such conditions.

"It is important to note that even if we really do a strong mitigation of greenhouse gases, the national park system is still expected to see a 2 degree temperature change," John Williams, a professor of geography at the University of Wisconsin-Madison and a co-author on the study, said in the Berkeley statement. "At this point, it is likely that the glaciers in Glacier National park will ultimately disappear, and what is Glacier National park if it doesn’t have glaciers anymore? So I think this adds weight to the importance of reducing our future levels of climate change and also extends the National Park Service mission to both adapt to these changes and educate all of us about these changes."

Why climate change hits national parks harder
Average temperatures in U.S. national parks have increased at twice the rate as the rest of the nation while rainfall has decreased.