Environmental Issues: Wildlands

Prolonged heat and drought could combine to kill forests, reduce river flows and keep visitors from enjoying archeological treasure troves.

Heat and drought have created a uniquely resilient landscape on the Colorado Plateau. In one cloudburst, a dry arroyo becomes a rushing stream that feeds countless plants and animals. Resourceful mountain lions and coyotes prowl through pine scrub for shade and quarry. With just drops of water, wildflowers can burst into vibrant hues of purple and red. These hardy species have adapted to extreme conditions, but even they may be pushed past their limits by global warming. Researchers believe that climate change will bring especially severe conditions to the Southwest. Heat and drought are likely to operate in tandem and compound each other, potentially killing entire forests and making the archeologically rich national parks of the region too hot for people to enjoy.

Scorching Temperatures Make Parks Intolerably Hot

The world-famous redrock of Delicate Arch in Arches National Park draws thousands of visitors every year. The hike to this sculptural wonder often involves scorching sun, thirst-inducing dryness and temperatures than can top 100 degrees in the summer. For most, the rewards of the hike far outweigh the challenges. But as global warming turns up the heat in the Colorado Plateau, travelers may find many treasured national parks in the region too hot for comfort. According to some climate models, the Southwest may experience more warming than other parts of the country. One particularly detailed projection foresees average temperatures in the Southwest increasing by as much as 14 degrees or more by the late 21st century. Considering current temperatures in the plateau -- Zion National Park has average summer highs of 95 degrees to 107 degrees -- any additional heat will keep many people away and deprive them of the chance to see these stunning landscapes.

Cliff Palace, Mesa Verde National Park

Drought and Heat Lead to a Permanent Loss of Forests

In the searing sunshine of the desert, cool, shady forests offer precious refuge. Rising temperatures caused by global warming make these wooded retreats even more critical, but they also make them more endangered. From 2000 to 2003, extreme heat and drought combined to kill entire expanses of low-elevation forests across 60,000 square miles in the Southwest -- a loss that may be permanent. In parts of Mesa Verde National Park, more than one-half of the piñon trees died, and at one area in Bandelier National Monument, as many as 90 percent of the piñon died. When a severe drought killed ponderosa pines 50 years ago, the trees did not recover in Bandelier, suggesting that the lower-elevation, semi-arid forests may be especially vulnerable to permanent loss. Many of the 23 national park system units on the Colorado Plateau are at risk of similar wholesale loss.

Severe Storms Flood Ancient Artifacts

In a young country like America, it is hard to grasp a sense of ancient times -- unless you travel to a place like the White House cliff dwellings in Canyon de Chelly National Park. Sitting deep within the pink-tinted walls of the canyon, these finely crafted buildings date back to 700 AD, and were home to the Anasazi for almost 600 years. The sites -- and the more than 800 other rock images, pit houses and cliff dwellings in the park -- have provided critical clues about early American cultures. These clues may become harder to find, however, as global warming places the artifact-rich parks of the Colorado Plateau in danger. Climate change is very likely to lead to increased flooding, even here in the desert, where sudden and severe rainfalls are likely to pour down on already hardened soils. Particularly at risk, researchers say, are the ancient structures and undiscovered artifacts in Aztec Ruins, Bandelier, Canyon de Chelly, Casa Grande Ruins, El Malpais, Gila Cliff Dwellings, Hovenweep, the Navajo national monuments and Chaco Culture National Historic Park.

Drought Years Reduce Boating and Rafting

Ever since John Wesley Powell navigated his way through their raging redrock canyons, boaters have been drawn to the legendary waters of the Colorado Plateau. More than 9.6 million visitors come to Lake Mead and Glen Canyon National Recreation Area -- primarily for boating and rafting. Water sports here depend on the levels of Colorado River water stored in the parks' reservoirs. But a recent study revealed that global warming could lead to a 36 percent decline in the basin's water storage before mid-century. Recent history illustrates what that might look like. After years of drought, Lake Powell went from full in 1999 to 33 percent of capacity in 2005, with the lake's water level dropping 144 feet. To keep the lake open to boating, the Park Service spent $20 million to extend boat ramps, and a concessionaire spent $2 million to move a marina 12 miles. Another 300,000 visitors each year go white-water rafting and kayaking through the dramatic landscapes of Black Canyon of the Gunnison, Grand Canyon and Dinosaur National Monument. Their enjoyment depends on heavy spring runoff, but as more winter precipitation falls as rain rather than as snow, and as snowpacks melt faster, peak rivers flows are already coming earlier in the season, and could begin coming too soon for summer vacations.