“Plants are going to have to migrate on average 2,600 feet to remain in equilibrium with climate,” says Silman. “That’s a long way, and they have to get there by 2100.” By then, according to most climate experts’ predictions, the average temperature in the cloud forest will increase by four to seven degrees Fahrenheit.
Much of the information about the effect of changing climate on high-altitude forests doesn’t come from the Andes, which have been relatively little studied, but from Costa Rica. There, in the Monteverde cloud forest, the dry seasons have become longer since the mid-1970s and have coincided with a number of local extinctions. Researchers recently tied the widespread extinctions of endemic frog and toad species in Monteverde to climate change. Warming in the next century is predicted to move the base of the cloud forest in that part of Costa Rica about 1,000 feet upward. If the movement continues, the clouds may rise above the crest of the Cordillera de Tilaran, and the cloud forest will cease to exist.
At camp, University of Cuzco biol-ogists Mireya Raurau and Marlene Mamani press plant cuttings between sheets of newspaper. The pressing continues into the night. Much of the load will be shipped to specialists in Peru and herbariums around the world where botanists will attempt to tag known plant species and identify new ones. Silman has thus far found dozens of new plant species, a new genus of tree, and some major extensions of the ranges of known species.
The Peruvian researchers will stay here for a month. For our entire stay in the Callanga valley, I’ve been staring up wearily at a 9,100-foot ascent—the first stretch of the way back out. Rapp and Silman plan to do the entire hike, a distance of 30 miles, in a single day starting at 2 in the morning. I decide to leave a day earlier, on a more civilized schedule.
Silman arranges a mule and guides for my journey. Ten-year-old Tito and his 18-year-old sister-in-law Malta belong to a mule-driving family in Callanga. They hike this 30-mile trail for a living, taking the valley farmers’ goods to market. Malta has a load over her shoulder, which I assume is clothes or food. Then the bundle begins to cry. On the way up, Malta nurses the baby, holding him in her left arm while whipping the mule with a stick held in her right hand. With all of us shouting, whipping and pushing, the mule goes only five to ten feet before it stops and we have to repeat the whole process. Our ascent travels the same upward path that the cloud forest may have to take.
Silman and Rapp, bleary-eyed, catch up with us the next day. Silman says hello, then collapses spread-eagle on the ground. After a brief rest, we resume our trek out of the cloud forest. On the hills above, a farmer is burning forest to make way for crops. Satellite photos taken over South America have shown 6,000 fires burning in tropical forests in a single night. “You can’t stop them all,” says Silman.
Michael Tennesen, a writer and photographer based in Lomita, California, wrote about a 19th-century family of telescope builders in the October 2001 issue of Smithsonian.