Environmental Issues: Wildlands

Pest outbreaks, less snow and more wildfires could threaten grizzlies, bison and the iconic western wildlife that a third of the nation comes to Yellowstone to see.

From the grizzly bears lumbering through the forests to the bison herds blanketing Hayden Valley to the elk ambling around Mammoth Lodge, visitors to Yellowstone are almost guaranteed a sighting of an animal they might see nowhere else. The desire for one of these sightings is so strong that one-third of the American population will come to the park in their lifetime. Yet as global warming leaves its fingerprint around the park, the view awaiting these visitors is likely to change dramatically. More pest infestations, diminished snowfalls and more intense wildfires could threaten the habitat of some of America's most iconic wildlife species.

Beetle Outbreaks Threaten Critical Grizzly Bear Food Source

We've all seen pictures of grizzly bears fishing for trout in mountain streams or grazing on berries and moths in alpine meadows. But grizzlies have an even more important culinary secret to success: the nutrient-rich whitebark pine nut, which provides bears with much-needed fat reserves for their winter hibernation. Grizzlies find the pine nuts in high elevations, where the trees thrive in extreme winter conditions. Warming temperatures caused by heat-trapping pollutants, however, have left the whitebark pine vulnerable to the voracious mountain pine beetle, an insect that used to be frozen out of whitebark stands. That's no longer the case. Already, the scourge is spreading fast: researchers say the beetle is now reproducing at a four- to seven-times higher rate in whitebark pine -- a speed that could push the whitebark pines to extinction. Scientists have observed that when whitebark pine nuts are in short supply, grizzlies spend more time near people hunting for replacement foods. As a result of those encounters, humans kill nearly twice as many grizzlies during years when pine nuts are scarce.

Adult grizzly, Yellowstone National Park

Drier Conditions Lead to More Fires and More Park Closures

During the famous Yellowstone fires of 1988, the park had to close for the first time in its history, and visitor days dropped by more than 400,000 from the previous summer. Global warming intensifies three main causes of wildfires -- high temperatures, summer dryness and long-term drought. While wildfires are a natural part of a forest's growing cycle, unnatural increases in the number and severity of fires can lead to park closures, disrupting people's long-planned vacations. Dense, gray smoke from wildfires can also shroud the breathtaking views of mountain peaks and geysers that so many people travel to Yellowstone to see.

Shorter Winters Cut Down on Winter Recreation

Yellowstone is the most popular national park for snow-based fun. The chance to view wildlife in the quiet of winter, without the RVs and crowds of summer, draws more than 100,000 hearty souls each year. But winter has become warmer in Yellowstone, and the snow doesn't fall as early or as thick as it used to. Each year, the National Park Service opens the winter season when enough snow accumulates to allow for oversnow traffic. Twenty years ago, the season began in the middle of November, but for the past several years, the agency had to wait until the middle of December for enough snow. In 2005, the season didn't start until January 1st. Climate scientists predict that as global warming continues, winter will start even later and end earlier, shrinking the snow-based recreational season even further.

Warmer Streams Limit Fishing Opportunities

Yellowstone National Park is an angler's paradise. From the legendary cold-water depths of Yellowstone Lake to the thermal-fed Firehole River, the runs are full and the trout are large. Many trout varieties thrive here, thanks to the notoriously cold water and the late spring runoff. But global warming will likely raise water temperatures -- threatening these acutely sensitive coldwater species. A study by University of Wyoming scientists suggests that a 5.4-degree increase in summer temperatures would make more than half of the trout streams in the Rocky Mountain region too hot for trout.

Rising Temperatures Endanger Wildlife-Filled Mountain Meadows

Hayden Valley, in the heart of Yellowstone, is one of the largest open meadows in the West. This wide-open expanse of grasses, brilliantly colored flowers and sloping hillsides is home to some of the best wildlife viewing in the park: visitors can see grizzly bears, bison, moose, coyotes, pelicans and sandhill cranes. But climate scientists say that mountain meadows of the West are endangered by global warming. These meadows exist where the combination of heavy snow cover in the winter and a short growing season make it impossible for tree seedlings to survive. But the rising temperatures and shrinking snowfall brought on by global warming could cause trees to creep into Hayden Valley's meadow, choking out the open range animals depend on.