Natural Laboratory

Biologists are discovering that Yellowstone National Park’s relatively pristine condition makes it an ideal place to study the effects of global warming; what they’re learning may surprise you

03-15-2011 // Julie Cart

Castle Geyser erupts in Yellowstone’s Upper Geyser Basin. Scientists fear that changes in water flow brought to the region by global warming could reduce geyser eruptions.

DURING LONG DAYS shuffling between conference rooms and congregating to debate in hallways, scientists and academics meeting in Yellowstone National Park last September talked about the weather.

What got their attention was the sobering statistic that average annual temperatures throughout Yellowstone, especially on the park’s western borders, have risen 2 degrees F during the past 100 years, nearly two times faster than global temperatures have risen in the same period. It comes as no surprise, then, that officials in the region are strategizing about how to manage this changing landscape—and the wildlife in it.

While many scientists around the world study computerized climate-change models in the lab, in Yellowstone the phenomenon is front and center on the ground, affecting nearly all the park’s living creatures. “We are fortunate here to have a natural laboratory that is mostly in its original state,” says Kerry Murphy, a Yellowstone wildlife biologist. “It’s one of the few places in the United States where natural processes are allowed to operate.”

That quality makes Yellowstone an ideal place to study and track the effects of global warming. The park has become a focal point for climate science, as experts outside the park service converge there to chart even minute shifts, following the path of change throughout the entire 20-million-acre ecosystem that runs along the spine of the Northern Rockies.

Participants at last fall’s conference spent a lot of time talking about grizzly bears, concluding that although grizzlies are adaptable enough to cope with climate-driven shifts in food sources, the animals may have to alter their use of habitat to access new foods. This modification of established grizzly behavior could put the animals into more conflict with humans, which will likely increase bear mortality.

Wolverines, one of Yellowstone’s rarest mammals, may be more directly affected by climate change. This largest member of the weasel family shelters from March to May in areas with deep and persistent snow, which insulates its dens and protects its young. But it may lose that protection with decreases in snowfall, which may also increase competition for food between wolverines and other predators.

To meet the management challenges wrought by a changing climate, park staff is sifting through data regarding wildlife and the region’s ecology. “Given the record keeping and research that have gone on in Yellowstone for decades, the park is one of the best places in the United States to study how global warming is changing the natural environment,” says Tom France, NWF’s Northern Rockies regional executive director.

LEFT: One threat to the Yellowstone Ecosystem is the mountain pine beetle, which kills trees. Global warming is helping the beetles to expand into new habitat. Biologist Roy Renkin examines beetle damage to a lodgepole pine. RIGHT: The grizzly bear is an iconic Yellowstone species that could be affected by global warming. The bear is highly adaptable and may find new food sources, but the process of adapting to warmer climate may put the bear into more conflict with humans, increasing grizzly mortality.

The consequences of climate change are making themselves known at other national parks around the country. Experts believe that the ice fields at Glacier National Park in Montana may be gone by the end of the decade. The namesake plant at Joshua Tree National Park in California is disappearing, as are the big trees in the state’s Redwoods National Park. And increasing hurricane frequency and intensity is damaging parts of Everglades National Park. What scientists learn in Yellowstone may help guide responses to global warming in these and other parks.

A Warming Park

Not so long ago, scientists in the National Park Service found that discussion of climate change was unwelcome in their analysis of park problems. “We were advised not to use ‘climate’ and ‘change’ in the same sentence,” says Tom Olliff, who until recently was chief of Yellowstone’s Center for Resources. However, he says, when the Obama administration took office climate change moved to the forefront of staff discussions about resource protection.

The park service has beefed up its contingent of scientists monitoring global warming, and Olliff has been appointed to colead a regional multi-agency group based in Bozeman, Montana, that considers landscape-level issues across the West. He also collaborates with one of the federally funded climate-science centers, where studies in and outside Yellowstone park seek to track implications for wildlife and its habitat. “No longer can you ignore climate change as an influence on the landscape,” he says. “It has to be considered a potential driver of change.”

Yellowstone’s 2.2 million acres mark one of the few places left in the Lower 48 that retain a virtually intact ecosystem—a landscape where the hand of humankind remains light. The park’s strict federal protections have sustained a kind of Noah’s Ark of plants and animals largely unmolested by localized industrial pollution, seeping toxic damage or massive carbon emitters.

Imperiled Pines

Some global warming impacts are obvious to any park visitor. Warmer winters have allowed mountain pine beetles to move from lower lodgepole pine regions to the higher elevations favored by whitebark pines. As a result, Yellowstone’s insect-infested pines stand out as rusty brown sticks against the park’s lush meadows and green mountains. What’s not obvious is the desperate drama that accompanies an infestation. Trees already distressed by drought are more likely to be set upon by mountain pine beetles.

In one campground Roy Renkin, a biologist studying Yellowstone plants, uses a short-handled axe to shave off the bark of a sick-looking lodgepole pine that illustrates the anatomy of an attack. He finds a swarm of the one-eighth-inch bugs girdling the tree and boring through the outer bark. Females scrape out nuptial chambers—troughs in which they lay eggs. When all is ready, the females produce a pheromone that calls other beetles to the tree.

The followers likewise burrow in under the bark, leaving behind trails of frass—sawdust mixed with excretions. When beetles have overrun a tree, they emit another hormonal signal en masse, telegraphing to other insects that there is no more room. Once the young hatch, they eat their way out of the tree, creating meandering galleries that resemble intricate, shallow carvings.

A trumpeter swan stretches its wings in a Yellowstone kettle pond. As such ponds, vital to swan survival, shrink, swan numbers are dropping to their lowest level in 80 years.

Pine trees attempt to expel the beetles by secreting resin or pitch, which pushes out through the insects’ bore holes. Infested trees are easy to identify by so-called pitch tubes leaking all over their trunks. However, the effort to combat the pests expends energy and food. A tree may starve in order to defend itself.

The pine beetle infestation continues apace as the invasive insect moves to higher altitudes in the park, where rising temperatures protect beetle larvae from freezing.

Animals at Risk

Among the creatures affected by global warming is the park’s gray wolf. Olliff says that in recent years, a season’s entire wolf pup production has been lost to canine distemper. While the disease is not uncommon among wolves, he says, distemper has a temperature signature, and higher temperatures may play a role. For now, though, scientists can make only a theoretical connection between climate change and wolf pup mortality.

Climate change is spurring a handful of similar developments throughout the park, amplifying existing problems and in some cases creating new ones. In parts of the park, for instance, trees are marching into Yellowstone’s mountain meadows, filling in open areas that are critical to wildlife such as deer and elk. Green growth also is the trigger for deer and elk migration, and biologists worry that longer growing seasons could keep vulnerable species from moving to higher elevations where they may find shelter from predators.

“We have species that have very narrow habitats—wolverine, pika, cutthroat trout,” says Glenn Plumb, formerly Yellowstone’s chief of resources, adding that those animals already are stressed by invasive plants and animals. “What if climate change is a catalyst that gives an invasive species an edge over the native, beyond what they already have?” he asks. “Now you have the potential of a devastating one-two punch.”

Plumb recently assumed the newly created role of chief wildlife biologist for the park service. From this position he oversees a suite of baseline surveys of often overlooked species, such as amphibians and bats, that may feel the effects of climate change more acutely than do large mammals. “We’re launching new studies across a whole range of areas, so we have a comprehensive analysis of what’s happening,” Plumb says.

Brownish expanses on Yellowstone slopes show where mountain pine beetles have killed off whitebark pines. Warming temperatures have allowed beetles to invade new regions.

Among other things, scientists are taking a close look at the park’s snow pack and its water systems and the implications for fish. Instead of the historically gradual thaw that metes out water over a manageable time, Plumb says, indications are that snowmelt now comes suddenly and disastrously at once, scouring streams and waterways, carrying sediment and dramatically altering the landscape of aquatic life. “That would change the nature of stream channels,” he says. “It could disrupt spawning. It could change the nature of hydrology here, the nature of our streams, the character and speed of the descent. So the suitability for spawning could change.”

Despite what biologists have been learning in the park, Yellowstone and its confrontation with global warming pose difficulties for park managers. Jon Jarvis, director of the National Park Service, says, “Climate change is going to be the most significant challenge to the fundamental premise and foundational management of our national parks that we have ever faced.”

“Yellowstone National Park is at the center of an enormous ecosystem that provides habitat for a wonderful diversity of fish and wildlife species,” NWF’s Tom France says. “Understanding the changes occurring there will give wildlife managers a chance to develop new strategies for protecting this diversity.”

Moreover, as the world’s first national park, Yellowstone has “an iconic image and message that cannot be overstated,” says Mike Clark, executive director of the conservation group Greater Yellowstone Coalition. “Because this is such a large park, and it has such different wildlife species, how the park service manages Yellowstone has a ripple effect throughout federal government. It sets the bar.”

Julie Cart is a staff writer for the Los Angeles Times.


How Global Warming Is Affecting Yellowstone

Officials at Yellowstone National Park are facing these challenges that evidence suggests may be caused or influenced by global warming:

• Many of the park’s drying creeks and rivers are no longer draining into Yellowstone Lake late in summer, cutting off native fish from spawning grounds and allowing nonnative trout to outcompete them. The consequences are still being studied.

• The number of heat-loving invasive plants in the park doubled during the past two decades as the aliens outcompeted native flora critical to overall ecosystem health. Some wildlife species are on the move, following the retreat of some trees and other plants to higher altitudes.

• Yellowstone’s kettle ponds, left behind by retreating glaciers, have been shrinking at an alarming rate. This decline has been one factor that reduced the park’s resident population of trumpeter swans, which rely on the bodies of water not just for nesting but also for escape from predators. Last year’s count of 9 swans was the lowest since surveys began in 1931 and represents a 73 percent decline in swans during the past decade.

• Pikas historically have lived on the park’s cooler rocky alpine slopes, a habitat that is being compressed as global warming raises the temperature of high-altitude zones. This change could jeopardize pikas. As a result, Congress recently funded a study looking at pikas and climate change.

• Finally, even Yellowstone’s Old Faithful is at risk. Park officials worry that the eruptions of Old Faithful and hundreds of other park geysers could soon diminish because the groundwater that regulates the geysers is receding.


NWF in Action: Protecting a Park in Peril

NWF, its field staff and its state affiliates have a long commitment to safeguarding Yellowstone National Park and its related ecosystem, which includes several national forests. Efforts to retire grazing permits have reduced conflicts between wildlife and livestock on more than 600,000 acres of habitat within the ecosystem. NWF has played instrumental roles in the protection of grizzlies and in the reintroduction of gray wolves to the park, where wild canines are helping to restore natural balances among elk, bison and other prey species. NWF’s larger campaign to reduce greenhouse gases and to develop clean-energy plans also will help Yellowstone and other wild areas by reducing the threat of global warming.

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