Death Valley National Park. Photo credit: Malee Oot.

By Malee Oot

Driving glacial retreat, sea-level rise, and loss of forest diversity, global climate change is already affecting ecosystems across America – especially in the country’s national parks. Now, a new study published in the journal Environmental Research Letters suggests America’s national parks are being more intensely impacted by climate change than the country as a whole, becoming both warmer and drier.

Led by Patrick Gonzalez, adjunct professor at the University of California, Berkeley, the study was the first to measure the impacts of climate change across all of America’s 417 national parks. Assessing trends in temperature and precipitation, the researchers looked at recorded historical data and made predictions about future shifts in the country’s national parks using four different emissions scenarios developed by the Intergovernmental Panel on Climate Change (IPCC).

Mount Whitney, located on the boundary of Sequoia National Park and Inyo National Forest. Photo credit: Malee Oot.

The authors found that between 1895 and 2010, America’s national parks warmed twice as fast as the country as a whole. Between 1950 and 2010, the most extreme rise in temperature was recorded at Alaska’s Denali National Preserve – and nine of the ten national parks experiencing the highest temperature increases were located in Alaska, the study determined.

Meanwhile, over the same period from 1895 to 2010, America’s national parks also experienced reduced rainfall – particularly locations in the southwestern United States, Alaska, and Hawaii, the study reported. Precipitation declined over 12% of the country’s national park areas, the study found, as compared to 3% for the United States as a whole. The most significant decrease in precipitation was observed at Hawaii’s Honouliuli National Monument.

Some of the ecological repercussions of climate change already recorded in national parks – shifting subalpine forests at Yosemite National Park, spates of bark beetles at Yellowstone National Park, and receding glaciers at Glacier Bay National Park – have occurred in locations where the authors also documented substantial temperature increases.

The study authors also looked ahead; at the ways, climate change will impact America’s national parks in the future, based on several different IPCC emissions models. Under the worst-case scenario – which assumes no effort is made to restrict greenhouse gas emissions – by 2100, temperatures could increase by as much as 9°C in America’s national parks. Under this worst-case emissions scenario, precipitation levels could also decline by as much as 28% in the national parks located in the U.S. Virgin Islands. Even under the reduced emissions scenario, temperatures could still rise by as much as 2°C over 58% of America’s national parkland, the study determined.

Ecosystems in national parks where models predicted the most significant temperature increases were found to be especially vulnerable. The authors caution that these vulnerabilities include Yellowstone National Park becoming increasingly vulnerable to wildfires, the large-scale loss of iconic Joshua trees from Joshua Tree National Park, and American pikas vanishing from Lassen Volcanic National Park in northern California.

Besides being home to some of America’s most unique natural wonders and cultural treasures, the country’s national parks also provide invaluable ecological services, the authors point out, including protecting the watersheds responsible for providing drinking water and helping to offset the impact of greenhouse gas emissions by storing carbon.

While raising the alarm about the potential future of America’s national parks, the authors also offer some hope. Compared to the worst-case scenario, cutting greenhouse gas emissions could decrease the rate of temperature change in America’s national parks by as much as one-half to two thirds by 2100, the study found.

Acting to reduce human-generated emissions now could spare America’s national parks from the most extreme temperature increases, and help to preserve the country’s public lands for future generations.