7. GREAT SMOKY MOUNTAINS
This park holds the planet’s largest stand of virgin red spruce and the southernmost vestige of Ice Age boreal forest. In fact, more tree species exist in the Smokies than in all of Europe, and more wildflower species (1,660) than in any other national park. There are 27 species of salamander. “It’s in between a lot of zones, with a lot of niche species at the end of their ranges,” says Don Barry. “It’s a great barometer for how global warming is affecting the richness of our wildlife–and it might give us signals about the bigger picture.”
Which is why researchers targeted the park for a huge, 100-plus-university study to catalog its species. Scientists predict that if CO2 levels double from 1961-1990 levels, as the IPCC models predict they will by the middle to end of this century, 16.7 percent of the park’s mammal species won’t survive, including the southern red-back voles and northern flying squirrels. A 3.6°F temperature increase, which could happen by the end of this century at current rates, could eliminate more than a third of native trout, which need cold, quick streams. Trees will begin migrating upward, seeking cooler temperatures; they’ll eventually overtake the Smokies’ iconic balds, along with species like the pygmy salamander that can only survive there. And what about the trees not near balds, with nowhere else to go? Species like the red spruce and the Fraser fir, which have already declined by 15 percent, won’t tolerate hotter, drier days, and their numbers will continue to plummet.
8. ROCKY MOUNTAIN
Because it’s so high–the main entrance is at 9,000 feet, and 11 percent of its area is open tundra–this Colorado park hasn’t seen the same glacier and snowfield retreat as Glacier and North Cascades. But spring runoffs are still starting earlier every year. With a 3.6°F temperature rise, they’ll arrive three to four weeks earlier than they do now; a 7.2°F spike will push them six to eight weeks ahead of schedule (the IPCC predicts the planet will warm 2.5°F to 10°F by 2100). On the plus side, the hiking season will be much longer. “This year, the Loch Vale Trail was snow-free in mid-May,” Baron says of the route from Glacier Gorge Junction to the Loch. “I remember walking on snow in early July. So we’re now seeing examples of what the future will be like.”
But that’s a silver lining in a rather dark cloud: fire danger. Some experts predict that for every degree Fahrenheit of warming, the park’s treeline could rise 250 to 300 feet, with savanna woodland replacing boreal forest and limiting tundra to isolated patches. A 9°F rise could eliminate all tundra. Already, krummholz–the stunted trees that hug the ground at treeline–are advancing, and will eventually wipe out many of RMNP’s open ridges and classic Colorado vistas. And the famous high-alpine wildflowers? John Harte, who’s spent 14 years artificially warming plants and soil with heat lamps at the Rocky Mountain Biological Laboratory in Gothic, CO, predicts that in 50 to 100 years the vivid displays could look more like lower-elevation sagebrush fields.
Thanks to naturalist Joseph Grinnell, who spent decades observing Yosemite–filling out 13,000 pages in his journal and collecting 20,000 specimens–we have a detailed catalog of what the park looked like 90 years ago. Now researchers from Berkeley are painstakingly re-surveying the ground he covered. Here’s what’s changed: Species are climbing higher to stay in cooler alpine conditions. American pikas, which used to be common at 7,800 feet, now only live above 9,500–and soon may have nowhere to go. Trees normally held at bay by a short growing season and a heavy snowpack are sneaking into signature meadows like Tuolumne. The trend may well continue: Several recent studies have concluded that 70 to 90 percent of the Sierra snowpack could disappear by the end of the century–meaning its renowned waterfalls will disappear far earlier every season, or become less spectacular.
10. JOSHUA TREE
California’s popular desert park has astonishing diversity: 700 plant species and 200 bird species, not to mention desert tortoises and bighorn sheep. But the most obvious climate-related threat is to the park’s eponymous tree. Kenneth Cole, a climate scientist with the Colorado Plateau Research Station in Flagstaff, warns that if warming trends continue, 90 percent of the park’s Joshua trees will be gone by 2100. Though they’re desert species, they need winter freezes to flower, and warm winters evaporate the moisture the trees need for survival. “The southernmost Joshua tree populations are perched at a critical threshold of high winter temperatures, and aren’t found in areas with temperatures above these limits,” Cole says. Since Joshua tree forests can only migrate about 32 feet a year, they won’t be able to shift north fast enough to survive.