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Living the high life: the mountaintop environment of the Andes harbors a Noah's ark of previously undocumented species
Natural History, Sept, 2006 by Kevin Krajick
Wind-driven hail lashes Preston Sowell and me as we top a 17,500-foot ridge in Peru's Cordillera Vilcanota. An avalanche thunders from a slope above--or was that real thunder? This close to the clouds, it can be hard to tell. I'm gasping in the thin air, and Sowell, a biogeochemist and mountaineer who works as a consultant in Boulder, Colorado, is on his twelfth ibuprofen for his throbbing, oxygen-starved brain. We're on what is perhaps an insane quest, but below we see what we are looking for--a grayish pool of water between ice cliffs and boulder fields. It might be the world's highest frog pond.
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We're part of a month-long expedition, pushing through the central Andes. The mountains are home to an astonishing variety of life-forms that survive amid thin soils, low oxygen, staggering winds, powerful ultraviolet rays, and surface temperatures that can plummet 90 Fahrenheit degrees when night falls. In this high zone there are hummingbirds with oversize wings to beat air that largely isn't there; spiders that wait for lowland insects to arrive on long-distance updrafts; microorganisms that eat rocks. The mountains around us are monstrous, but only the loftiest of them are cloaked in glaciers, thanks to the moderate precipitation and, just fourteen degrees south of the equator, the long days. (Not that ice stops life; biologists have found algae and invertebrates in and on Himalayan glaciers at least as high as 18,400 feet.)
"Mountains are hard to beat for biodiversity," Stephan R. P. Halloy, our chief scientist, has told me. One reason is that every 1,000-foot rise in elevation is the rough equivalent of a 150-mile journey away from the equator--so ecosystems in the mountains get stacked vertically. And the land area decreases as you climb, so new climate zones at successively higher elevations are confined to successively smaller plots. The highest zone, the alpine zone, covers only 3 percent of Earth's landmass, yet perhaps 10,000 plant species live there--many evolving on just one or two islandlike peaks, separated by oceans of lowlands.
Halloy, an alpine ecologist who consults for the World Wildlife Fund and teaches at San Andres University in La Paz, Bolivia, seems specifically evolved, too. A Belgian raised in Africa, the United States, and Argentina, he was just twelve when he started helping his herpetologist father with high-elevation work. While others in our party labor upward with heavy boots and trekking poles, and sleep in all-weather tents, he lopes along in frail canvas sneakers, hands behind his back, chatting away as if giving a tour of his lab. He wears an altimeter around his neck like a religious medal, and sets his sleeping bag out under the stars most nights.
The co-leader of our expedition is Anton Seimon, a Columbia University geographer and climber who has organized scientific treks like this one through the Vilcanotas for the past five years. In 2004 he and his wife Tracie A. Seimon, a cell biologist also at Columbia, discovered tiny, unidentified tadpoles near our pond--apparently the world's highest known amphibians. Sowell and I hope to spot adults, to prove they are breeding here.
The higher you go, of course, the thinner the air. Animals and peoples of the high Andes (and in other high regions such as the Himalayas and the high Ethiopian plateau) have evolved bigger lungs or beefed-up blood chemistry for delivering more oxygen. Many low-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 11,000 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 invading 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 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 numbers 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 grazing 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.
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