land visitors can adjust to the altitude, but there are 

 limits. The ancient Inca capital of Cuzco, gateway 

 to the Vilcanotas, lies at more than 1 1 ,000 feet — 

 high enough to inflict fatigue, panting, nausea, and 

 heart palpitations on the unacclimated. Above 

 Cuzco, entire sectors of nature drop out. Most 

 reptiles cannot take the cold; neither can trees, 

 whose sap, even in adapted species, cannot flow in 

 temperatures much below freezing. In most places, 

 plant life begins to wink out altogether above 

 16,500 feet. It is too cold, and nutrients — even 

 soil — are too scarce. 



But our party has also been witness to change. 

 From Cuzco we reached the last-stop market town 

 of Sicuani and headed up a precarious dirt road. 

 Along the road we saw lowland competition invad- 

 ing the high realms. Everywhere, on terraces cut 

 into impossible slopes, Quechua-speaking farmers 

 had planted potatoes — the world's highest crop — as 

 they have for millennia. But in the past three 



Tarantula found at 14,700 feet in the Cordillera Vilcanota is 

 thought to be both a species new to science and the highest 

 tarantula species yet identified. The tarantula is already well 

 known to local Quechua inhabitants, however, who call it 

 campo-campo. 



decades the average temperature in the central 

 Andes has risen 1.8 degrees — far more than in most 

 of the rest of the world. As a result, farmers have 

 extended their fields up to 15,000 feet, from a 

 1970s record of 14,000 feet. Livestock is moving 

 up, too: at 15,400 feet, we began a three-day trek 

 across a great rolling plateau, where thin native 

 plant cover is being crew-cut by increasing num- 

 bers of domesticated llamas and alpacas. Their 

 cousin, the wild and woolly vicuna, is retreating to 

 the most extreme elevations. 



Even the glaciers that mark the end of the graz- 

 ing range are receding with accelerating speed, 

 some as much as 650 feet a year. Once forced to 

 the summits, like the animals, they may vanish into 

 thin air — a fate already predicted for lower-lying 

 glaciated ranges in Europe, New Zealand, and 

 North America by the end of this century. For 

 now, though, the lofty Vilcanota chain — whose 

 highest peak, at 20,944 feet, is Ausangate — is still 

 capped by the tropics' greatest ice masses. (In 

 Spanish, a peak such as Ausangate is called a nevado, 

 which means "snow-covered.") Here, the alpine 

 biosphere is still just rising, not disappearing. 



Near the end of our hike up a long, high valley, 

 we saw plants thinning to bare stone and 

 distant clouds of sunlit snow blowing off the peaks 

 like flares. There we met our last local inhabitant. 

 Mario Condore Ya, a thirtyish herder, pointed 

 ahead to our destination. "I don't go up there," he 

 said. "There is nothing for the alpacas to eat." He 

 gave a whistle, and his herd started trotting toward 

 him from a half-mile away. 



But there is life up there. Another member of 

 our team, Steven K. Schmidt, a microbiologist at 

 the University of Colorado at Boulder, and his 

 graduate students have shown that many high 

 slopes of bare-looking sand and scree teem with 

 previously unsuspected microscopic life. Bacteria, 

 fungi, and protozoa all thrive — in such volume 

 that they may play major roles in the water chem- 

 istry of the surrounding lowlands and even in the 

 cycling of global nutrients. 



At about 16,000 feet, after crossing a mile-long 

 jumble of newly melted-out glacial debris, we 

 reached the fast-wasting ice front close to the head 

 of the valley I hopped onto a solid-looking sand- 

 bar — and promptly sank to my knees in quicksand. 

 That hazard, I learned, is common in the fine de- 

 bris eroding out of ice fronts. After I wrenched 

 myself free, Schmidt told me that the microorgan- 

 isms in the mud now mucking up my boots prob- 

 ably originate in or under the ice. The ice is also 

 releasing pollen, trapped in the glacier as it 



46 



NATURAL HISTORY September 2006 



