Climate Change is Reshaping U.S. National Parks

Standing in awe in California’s Yosemite Valley or in the shadow of Denali, deep in the Alaskan interior, it is easy to imagine that the 60 national parks of the United States are pristine wildernesses. However, what many don’t realize, is that the national park system actually encompasses over 400 units, including historical sites, battlefields, and scenic trails. Even the 60 sites that include ‘National Park’ in their name – think Acadia in Maine, Virginia’s Shenandoah, or the ‘Mighty Five’ parks in southern Utah – are less untouched than we’d like to imagine. The wolves that are so integral to the ecosystem and tourist experience in Yellowstone, Wyoming were brought there less than 30 years ago from Canada after a 70-year absence from the park. The inhospitable Grand Canyon, deep in the deserts of Arizona, provided a permanent home to Native Americans for at least 4,000 years before it became a park. And, since 2000, the largest restoration project ever undertaken in the US has been underway in the endless expanse of the Everglades in south Florida. The truth is, our national parks have never been able to avoid, and in many cases have benefited from, human intervention. However, with climate change, these iconic landscapes are now facing new threats stemming from human activity that may permanently alter the parks and our relationship to them.

Because of their active management, relatively intact ecosystems, and the presence of long-running scientific experiments, national parks have served as valuable laboratories to understand the myriad impacts of climate change. They’ve also given scientists and visitors alike a front row seat to those impacts as these landscapes change before our very eyes. In Alaska, melting permafrost, rapid coastal erosion, and disappearing sea ice are destroying archaeological sites and disconnecting native people from their historical subsistence lifestyles (some Alaskan parks are open to hunting by Alaskan natives). In Glacier National Park in Montana, only 25 of the park’s titular glaciers remain, compared to 150 in the late 1800s. Scientists project that all of the remaining glaciers could be gone in just 15 years. And in California’s Sequoia National Park, average annual temperatures are expected to rise by 7 degrees Fahrenheit by 2100, threatening most of the 65 groves of Sequoia trees that exist in the entire world.

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Photo: Glacier National Park’s Boulder Glacier in 1932 (top) vs. 1988 (bottom). Boulder Glacier is no longer considered an active glacier. Photo Credits: (top) Glacier National Park and (bottom) Lisa McKeon via Climate Central.

While the specific impacts of climate change, and the severity of those impacts, vary geographically, most parks are expected to experience, unsurprisingly, some warming. In fact, the acreage managed by the National Park Service has warmed faster since 1895 than the rest of the United States. For example, since 1948, the average annual temperature in the Greater Yellowstone Ecosystem, which spreads across Wyoming, Idaho, and Montana and includes Yellowstone and Grand Teton National Parks, has risen about 2 degrees Fahrenheit, and winter is on average 10 days shorter a year. In mountainous parks like Yosemite and Glacier, rising temperatures have also changed the timing and availability of the winter snowpack, with more precipitation falling as rain than as snow. In fact, snowpack in the northern Rockies region today is at its lowest level in eight centuries. This, in turn, increases the likelihood of catastrophic flooding during the spring melt season and terrible drought in the late summer. Increases in summer temperatures are expected to shift visitation patterns, with more tourists coming in the fall and spring shoulder seasons rather than in the peak of summer. Currently, the Park Service estimates that the main visitor season will grow by 13 to 31 days across all of the parks. While that change may be an economic boon from gateway communities, it could stretch existing services thin as park managers attempt to accommodate more people over a longer season.

In 2016, Climate Central, the nonprofit climate news service, released a report analyzing the impact of rising summer temperatures on parks in the Lower 48, assuming greenhouse gas emissions remain steady. They found that summer temperatures could be up to 12 degrees Fahrenheit warmer in some parks by 2100. They also found that there’ll be a dramatic increase in the number of extreme heat days, which is especially problematic for summer visitors. The most significant increase in extreme heat days will be felt in Texas’s Big Bend National Park, where the average number of days above 100 degrees will increase from 17 a year (from 1991-2010) to 113 in 2100. Arizona’s Saguaro National Park will similarly experience an increase from 39 to 127 days a year. Meanwhile, the number of days over 90 degrees in North Carolina and Tennessee’s Great Smoky Mountains, the most popular national park in the country with over 11 million visitors in 2017, could increase from 10 days to three months a year by 2100. At this rate of warming, summer time in Acadia National Park will feel more like that in southern Maryland, while Ohio’s Cuyahoga Valley will feel more like the Gulf Coast of Texas.

These increases in air temperature will increase the temperature of streams and rivers, affecting downstream commercial and recreational fisheries, and lead to an expansion in the range of invasive species and pests. For example, without the cold flow of glacier melt every summer, the western glacier stonefly, unique to Glacier National Park, is inching towards extinction. Bull trout throughout the mountain West are also struggling with warmer temperatures and an explosion of invasive lake trout populations. Meanwhile, invasive plants like cheatgrass have moved in en masse, pushing out more fire tolerant and nutritious native grass species. Warmer temperatures and extended drought have also led to infestations of mountain pine beetle across the West, particularly in high elevation forests that lack natural defenses against the pests. Over the past 30 years, the pine beetles have chomped over 46 million acres of forested land, infecting almost all of the pine trees in Colorado’s Rocky Mountain National Park and 80% of the whitebark pines in Yellowstone. Widespread tree morality not only increases the risk of wildfires, by providing more dry fuel to burn, but it also takes away an important food source for species like grizzly bears, which rely on pine cones as a staple of their diet.

Map shows the impact of Pine Bark Beetle infestations in the West from 2000-2014. Image Credit: Karen Minot via MotherJones

Rising temperatures and the expansion of grasslands also provide the perfect conditions for devastating wildfires. Across the country, the average annual number of fires larger than 1,000 acres has more than tripled since the 1970s. In the northern Rockies, specifically, it has gone up more than 10-fold. Fire season is now 105 days longer than in the 1970s, with some fire managers claiming that there really isn’t a discrete fire ‘season’ anymore. With these changing conditions, fires like the catastrophic Yellowstone fires of 1988 and the 2013 Rim Fire in California, which burned almost 80,000 acres of Yosemite, are likely to become all too common.

Combined, these changes will shift what biologists call the ‘green wave.’ The green wave is not just a college mascot, but an important ecological process whereby plants become green at different times at different elevations, driving the hibernation, reproduction, and migration patterns of animals. A change in the green wave, coupled with changes in water availability, may alter how and when animals migrate through the landscape. Already, drought conditions are shifting the annual migration of Yellowstone’s elk. Meanwhile, an increase in icy conditions (from more rain-on-snow events) will make it more difficult for the caribou herds in Alaska’s Gates of the Arctic National Park to dig for food in winter. In many states, national parks provide a refuge for large animals that are threatened by hunting and development outside of park borders. This is especially true for animals with long migration routes like the pronghorn (who have the longest land migration in the continental US) or bad reputations like wolves, that can be shot by hunters when they follow their elk prey beyond park boundaries. These uncertain changes to migration patterns will diminish the capacity of parks to provide safe havens that ensure these species and others can thrive.

The remote, high-elevation and forested parks of the West are not the only ones under siege. These same threats – invasive species, warming temperatures, changes in water availability – are affecting parks in every state. At the same time, parks protecting coastal and wetland ecosystems are also struggling with the additional burden of sea level rise. For example, New York City’s Gateway National Recreation Area – the only park service unit one can reach by subway – is preparing for sea level rise of 3 feet by 2100. That level of rise would put roughly $1.5 billion of assets at the nearby Statue of Liberty National Monument at risk. Those parks are having to find a way to adapt to the slow onset rise of sea level, while also shelling out millions for recovery from the devastation of Hurricane Sandy in 2012. Managing steady sea level rise, coupled with an increased risk of saltwater intrusion and a more intense hurricane season, is a challenge all the parks on the Atlantic and Gulf Coasts, including Florida’s Biscayne National Park and Louisiana’s Jean Lafitte, will have to confront.

Climate change is likely to permanently alter the landscapes of our iconic national parks across the country. And in most cases, ecosystems are transforming so rapidly that many species don’t have the time or capacity to adapt. The Park Service is already having to rethink the entire paradigm around which we manage national parks and preserve the plants, animals, and human communities that call them home. Increasingly, park managers are turning to scenario planning and other innovative approaches to account for the vast uncertainty they face, both in terms of how these ecosystems and the federal government will respond to change. If anything, though, the threats of climate change will make the park system more vital than ever. Vast tracts of undeveloped land and robust, well preserved green corridors between protected areas will leave more physical space for species to migrate and adapt in response to changing conditions. National parks can and must continue to serve as refuges for species already stressed by development and habitat loss for whom climate change could otherwise be a death sentence. While these landscapes will change, they may, with the proper adaptation strategies and proactive response of local, state, and federal government, continue to remain iconic landscapes for generations to come.

Learn more about what impact climate change will have on individual national parks and what the National Park Service is doing about it here.

Featured Image: Sequoia National Park by Tuxyso / Wikimedia Commons, via Climate Central

About the Author: Leah Campbell is a first-year Ph.D. student in the Department of City and Regional Planning, where she focuses on equitable climate adaptation and disaster mitigation. Prior to UNC, she worked in the environmental nonprofit sector in California after receiving her B.S. in Geophysics and Environmental Science from Yale in 2015. Outside of academics, Leah enjoys folk music, long road trips, and anything that gets her outside.


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