Published online 12 January 2011 | Nature 469, 150-152 (2011) | doi:10.1038/469150a
Corrected online: 4 February 2011

News Feature

Conservation biology: The end of the wild

Climate change means that national parks of the future won't look like the parks of the past. So what should they look like?

Imagine Montana's Glacier National Park without glaciers; California's Joshua Tree National Park with no Joshua trees; or the state's Sequoia National Park with no sequoias. In 50 years' time, climate change will have altered some US parks so profoundly that their very names will be anachronisms.

Jon Jarvis, who became director of the US National Park Service in 2009, has called climate change "the greatest threat to the integrity of our national parks that we have ever experienced". The sentiment represents a dramatic shift from the position held during the Bush administration, when officials refused to fully acknowledge the existence of climate change. Now, park managers in the United States and around the world are working with researchers to map how the landscapes they care for might change. And they are coming to terms with the idea that the historical remit of most parks systems — to preserve a piece of land in its 'natural' state — is untenable. "You can't fight the climate," says Ken Aho, an ecologist at Idaho State University in Pocatello, who studies non-native species at Yellowstone National Park in Wyoming. "Eventually you have to throw up your hands," he says.

Nowhere is attachment to historical fidelity more pronounced than at Yellowstone, the first US national park and the best example of the park as a landscape seemingly unchanged by the passage of time. Visiting it, one crosses paths with bison and wolves. It is not hard to imagine a party of explorers coming around the next bend.

Much of Yellowstone's 900,000 hectares are high plateau, crossed by rivers and dotted with geothermal basins featuring pools and geysers. The park was created in 1872, to protect the geological wonders and safeguard a wild landscape emblematic of the American west. Since 1916, Yellowstone and the nation's other parks and monuments have been run by the National Park Service, which has aimed to preserve the land in its 'natural' condition — typically meaning how it looked before white people arrived. In the words of the influential Leopold Report of 1963: "A national park should represent a vignette of primitive America." (A. S. Leopold et al. Wildlife Management in the National Parks Advisory Board on Wildlife Management; 1963.)

Click for larger image

But Yellowstone can no longer be kept as it was in 1872, if that were ever possible. Climate change has already begun to transform the park (see 'Under attack'). The Yellowstone area has been plagued by tree pests, abetted by warmer temperatures. Fires are expected to become more frequent, animal populations are shifting and the landscape and ecology are being reshaped. Similar stories are playing out at all of the nation's parks, and the Park Service is beginning to react. In September 2010, it released a Climate Change Response Strategy, which includes sections on science, adaptation, mitigation and communication (National Park Service Climate Change Response Program; 2010). The report hints that climate change may force the Park Service to change the way it defines its mission. Maintaining a natural state can no longer be the goal, or important tools for adaptation, such as moving species or selective breeding, would be forbidden. And besides, that battle may already be lost.

Encroaching damage

A drive through the greater Yellowstone area reveals changes to the landscape. Most striking are the acres of trees standing dead, killed by an insect the size of a grain of rice. Mountain pine beetles, native parasites, burrow into and reproduce in the living wood of the trees. Winter temperatures of −40 °C kill the beetles, keeping their numbers down. But warm winters in the past ten years have allowed them to proliferate. More than half of the greater Yellowstone ecosystem's conifer forest has seen pine-beetle damage, and 10% of the forest has a 'high severity' infestation, in which more than 40% of trees are lost. Throughout the western United States, the Park Service has used insecticides to protect some trees, and removed a few dead ones. Mostly, however, it can only watch as an orange wave of dying trees ripples through the forest.

Climate change may increase the frequency of intense fires similar to the historic 1988 blaze (top) and may promote destruction of the trees by mountain pine beetles (bottom), which flourish in rising temperatures.Top: J. Henry/A. Henry/; Bottom: R. Perry/New York Times/Redux/Eyevine

The dried-out remains left in the beetles' wake look like an invitation to intense forest fires that would reshape the landscape even more, but that is not necessarily the case. Monica Turner, an ecologist at the University of Wisconsin–Madison, has been modelling big blazes at Yellowstone, such as the inferno of 1988 that burned 321,000 hectares of forest. She and her colleagues have found that such fires burn in the living crowns of trees and don't rely on dead wood; furthermore, pine-beetle attacks kill trees, decreasing the amount of wood in an area and creating gaps that can stop a fire.

Even so, Turner's group expects that the big fires that typically occur every few hundred years might happen more frequently in the future without the beetles' help, thanks to increased temperatures and changes in precipitation levels. That increased frequency might turn some parts of Yellowstone into a landscape of young forests, with less capacity than more mature ones to absorb carbon dioxide from the atmosphere. This could potentially turn the park at large from a carbon sink into a carbon source.

But forecasting the future is complicated. Pines that don't get caught in a blaze may actually grow better in a warmer future; growth of lodgepole pines is limited by the length of the growing season and by cold temperatures. Meanwhile, species such as the larch, currently confined to lower altitudes than those at Yellowstone, may move up as temperatures rise.

Other familiar tree species might go locally extinct. Whitebark pine, a high-altitude species, is facing a three-way attack from pine beetles, a fungal disease called blister rust and climate change. As Yellowstone's peaks heat up, the tree's range is expected to move upslope, but the higher it goes the less area it will have. "The future of whitebark pine in Yellowstone is questionable," says Turner.

Ecosystems won't move predictably. "Migration in response to climate change can often be extremely messy," says Stephen Gray, a climatologist at the University of Wyoming in Laramie, who is among those working on scaling down global climate models to forecast changes at the level of individual parks.

As ecologists scramble to predict changes, park managers are gearing up for a new management style, which will have to include at least one of two approaches traditionally anathema to the profession: letting things change, or intervening aggressively to keep them the same. In many cases, choosing between these strategies will be the challenge.

If managers choose the former, they will need to create an environment conducive to change. For example, many conservation biologists argue for creating and maintaining corridors that connect parks to other natural areas. The bigger the connected area, the more room plants and animals will have to move and the larger the gene pools available for adaptation.

Wolverines are one species that might benefit. Maps of future climates suggest that by 2040, lower-elevation parts of their current range may no longer have the deep spring snow that wolverines need to make their dens. So managers should perhaps focus on increasing the quality and connectivity of land in the Colorado Rocky Mountains, California's Sierra Nevada and parts of Wyoming and Utah to make sure that the wolverine population remains large enough to be genetically healthy.

To maintain corridors in areas that fall outside national-park remits, the Park Service is participating in Landscape Conservation Cooperatives, an initiative begun in September 2009. These clubs of federal and state agencies, conservation organizations, university scientists and other interested parties focus on managing huge chunks of land as units, rather than having every park, forest and piece of private land managed independently.

A firm hand

But tough choices loom in terms of how much to meddle. Aggressive intervention might be needed to conserve some of Yellowstone's larger mammals (see 'Four seasons of worry for the grizzly') and its iconic trees. To preserve the whitebark pine, some scientists from various agencies have begun identifying trees that are resistant to blister rust and collecting seeds to breed rust-resistant trees. They've also begun planting whitebarks in newly burned areas. They plan to use insecticides to protect individual trees from pine beetles, prune off infected branches and thin the vegetation around the trees to give them a competitive advantage. They also plan to stop fires from burning rust-resistant or particularly genetically diverse stands of whitebarks. Some of these planned actions sound a lot like landscape gardening.

The alternative approach would be to let the whitebarks die out in Yellowstone, and plant them somewhere where they might flourish in a warmer future. Sally Aitken, a forest geneticist at the University of British Columbia in Vancouver, Canada, has planted whitebarks beyond their current range, in northwestern British Columbia. They seem to like it there.

Jarvis has suggested the possibility of moving species outside their native ranges to give them a better chance of surviving — just not right away. "The big point here is that we are willing to face these questions," he says. "We are not afraid to talk about them."

Other countries have ditched 'naturalness' for goals that encompass a range of acceptable states, and don't rule out aggressive intervention. Parks Canada uses an 'ecological integrity' approach, preserving a configuration of local flora and fauna that is likely to be robust.

At a conference on the Yellowstone ecosystem last October, many speakers talked about managing for 'resiliency' rather than historical fidelity, promoting an ecosystem's ability to change with the times without changing in character. Rather than trying to sustain a stressed ecosystem that collapses at the first hot summer, the idea is to let things change gracefully.

But the Park Service isn't planning to change its mission any time soon. "I don't think resilience replaces our current management foundation," says Jarvis. "Our goal has never been to freeze [parks] in some kind of stasis."


Resiliency may be achievable for Yellowstone, even if it won't look like it did in 1872. Whitebark pines may not make it, but lodgepole pines are very resilient. Bears and wolves are clever. Yellowstone is big and Yellowstone is tough.

"As a scientist who really treasures the region," says Turner, "I believe that Yellowstone will go on in the face of climate change. Yellowstone is very resilient. The 1988 fires are not a catastrophe. Bark beetles are not a catastrophe." 

See Editorial page 131


The graph 'Under attack', which appears to show a correlation between rising minimum temperatures in Wyoming and increased survival rates for mountain pine beetles, should have made it clear that the beetle data were modelled not measured.
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