Yellowstone a petri dish for climate change
Roy Renkin is a biologist by training but a detective by inclination, and something about the willows was nagging him.
The shrubs flanking a creek in Yellowstone’s Blacktail drainage had never grown so tall and lush. But why?
Many of the park’s scientists theorized it was related to the successful reintroduction of wolves, which might have pushed elk out of the area, putting an end to the constant nibbling that stunted willows’ growth.
But this summer, Renkin and a colleague arrived at their own theory: climate change.
Warmer temperatures have extended the park’s growing season for plants by up to 30%. Renkin found that given the additional growing time, willows produced powerful defensive compounds that made them unpalatable to wildlife, enabling some to grow more than twice as high.
The tentative findings are a small piece of a much larger climate puzzle whose effects are making themselves known at national parks across the country. In some cases, the changes are imperiling the very features that define some of the nation’s most-beloved parks.
The ice fields at Glacier National Park in Montana are quickly fading and may be gone by the end of the decade. In California, the namesake plants at Joshua Tree National Park are disappearing, as are the big trees at Redwood. Increasing hurricane frequency and intensity is destroying the Everglades in Florida.
But, because of a number of unique factors, all eyes are on Yellowstone to lead the way in understanding climate change.
Yellowstone’s 2.2-million carefully managed acres are among the few places left in North America to retain a virtually intact ecosystem, in a landscape where the hand of man remains light. The park’s strict federal protections have maintained a refugium -- a kind of Noah’s Ark of plants and animals whose lives are largely unmolested by localized industrial pollution.
“We are fortunate here to have a natural laboratory that is mostly in its original state,” said 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 approach has support in Washington from newly installed park service Director Jon Jarvis. “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,” he said.
As more and more climate research originates in the park, subtle changes are coming into focus. Yellowstone officials are quick to say that not all of the unexplained transformations here have a direct link with climate change. Scores of effects have yet to be extensively studied, they say. But park managers point to a host of worrisome changes.
With food sources and hospitable weather lingering well into fall, Yellowstone’s grizzly bears are retiring to their dens later than ever before. In September, a federal judge ordered the region’s grizzlies back on the endangered species list, in part because of climate change.
Aided by warmer weather and the easy pickings of drought-stricken trees, beetles are ravaging the park’s pines; a 50% mortality rate among mature trees is destroying grizzlies’ most important food source.
The population crash of pikas, small rabbit-like mammals that have historically lived in the park’s rocky alpine slopes, has led to their being considered for inclusion on the endangered species list, the first animal in the lower 48 states whose extinction threat is pegged to climate change.
The number of heat-loving invasive plants and weeds has doubled in the last two decades, out-competing native flora that are crucial to overall ecosystem health.
Yellowstone’s complex water network also shows signs it has been thrown out of kilter, initiating a host of concerns about rippling effects as the course of the park’s lifeblood is altered. Many of the park’s dwindling creeks and rivers are no longer draining into Yellowstone Lake, cutting off native fish from their spawning grounds.
Yellowstone’s kettle ponds, formed by retreating glaciers, have been shrinking at an alarming rate. This has reduced the population of trumpeter swans, which rely on the bodies of water not just for nesting but also as a refuge from predators.
The park’s iconic Old Faithful is also at risk. Park officials worry that receding groundwater levels -- which regulate Old Faithful and hundreds of Yellowstone’s other geysers -- could soon diminish their dramatic displays.
Not long ago it was impolitic for scientists in the National Park Service to consider climate change in their analysis of park problems.
“We were advised not to use ‘climate’ and ‘change’ in the same sentence,” said Tom Olliff, chief of the Yellowstone Center for Resources. But the Obama administration has made climate-change science a priority, Olliff said, so now the issue is at the forefront of staff discussions about resource protection.
Experts outside the park service are converging here to chart even minute changes, following their significance in the entire 20-million acre ecosystem that runs along the spine of the northern Rockies.
The park is one of 20 U.S. sites selected to be part of the National Ecological Observatory Network. The observatory in Yellowstone will gather extensive ecological and climate data, which will be collated with information from sites around the continent and used for detailing and forecasting wide-scale ecological and climate shifts.
Some consequences of climate change are obvious to any visitor. Yellowstone’s insect-infested pine forests stand in rusty brown relief against the park’s 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.
Carrying a short-handled ax, Renkin approached a dying pine and after a quick chop, revealed the anatomy of an attack. Swarms of the bugs -- each an eighth of an inch -- girdled the tree, boring through the outer bark. Females scrape out “nuptial chamber” troughs in which their eggs are laid. When all is ready, the females produce a pheromone that calls male beetles to the tree.
Once the young hatch, they eat their way out of the tree, creating meandering, intricate “galleries” that look like delicate shallow carvings.
The pine tree has little defense against such an insect barrage. A healthy tree will attempt to expel the beetles by secreting resin, or pitch, which pushes out through the insect’s bore hole. Infested trees are easy to identify by “pitch tubes” leaking all over their trunks. However, the effort to rid itself of the pests expends energy, water and nutrient stores. The struggling tree may starve itself in order to defend itself.
Climate change is spurring a handful of similar developments throughout the park, amplifying existing problems and, in some cases, creating new ones. Trees are growing in Yellowstone’s mountain meadows, filling open areas that are crucial to the livelihoods of some wildlife.
Olliff said that in recent years a season’s entire wolf pup production was lost to canine distemper or parvo. Park scientists have noted an increase in the spread of the disease as temperatures rise, he said, but right now climate change is only a theoretical culprit.
“We have species that have very narrow habitats -- wolverine, pika, cutthroat trout,” said Glenn Plumb, Yellowstone’s chief of resources, adding that those animals are already stressed by invasive species of 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 asked. “Now you have the potential of a devastating one-two punch.”