Title: Uphill Battle
Author: Michael Tennesen
Source: SMITHSONIAN, August 2006 pp 78-83
Data Base: C

Uphill Battle

(As the climate warms in the cloud forests of the Andes, plants and animals must climb to higher, cooler elevations or die.)

by Michael Tennesen

On the crest of the Eastern Andes, about an eight-hour drive on a dirt road from Cuzco, Peru, is an expansive vista of the most diverse forest on earth. I look out over the mountains and see 10 or 20 miles into the Amazon Basin before the view disappears in the rising mist. Storm clouds boil up in the pink evening sky, and fog advances over the foothills. The rain and fog suffuse the mountains with the moisture that makes them so astonishingly full of life.

Miles Silman, a biologist from Wake Forest University in North Carolina, brought me to this ridge to introduce me to the cloud forests of Peru. They proliferate among clouds born of moisture rising from the Amazon Basin. The constant misting sustains a great variety of trees, which in turn support ferns, mosses, bromeliads and orchids that struggle to lay down roots on any bare patch of bark. It's these epiphytes ("epi" means "on top of" and "phite" means "plant"), plus the wet humus soils, the thick understory of plants and the immersion in clouds that distinguish cloud forests from other types of forest. Because cloud forests are so rich and varied, and difficult to explore, and because so few scientists have been here, relatively little is known about them. Only those in Costa Rica and Puerto Rico have been well studied.

Silman and other scientists are attempting to catalogue and understand plant and animal life in Andean cloud forests before it's too late. As in many wild places, the researchers who work here feel that their task is urgent. Oil companies, having found petroleum and natural gas in the surrounding lands, are cutting roads and pipelines through the cloud forest that scientists say are damaging some plant populations and localized species. Also, native farmers and ranchers harvest the cloud forest for firewood and room to expand.

Most significant, the Andes cloud forests are threatened by climate change. In other parts of the world, warmer temperatures in the past century have pushed native species toward the poles or altered their growth and migration. In North America, for example, the ranges of the blue-winged warbler and other songbirds have shifted north; barn swallows and other birds are migrating earlier in the spring than they once did; and plants are sprouting and blooming sooner. But some scientists say cloud forests are particularly vulnerable to climate change.

Of 25 biodiversity hotspots worldwide that conservation groups say deserve special protection, the high Andes is the richest and most diverse by far, says Lee Hannah of Conservation International. The region has almost twice as many plant species and four times as many endemic plants-native species found nowhere else in the world-as the next place on the list, Mesoamerica (Central America and Southern Mexico).

Many of the Andean plants have "shoestring distributions." The area where they can root, grow and reproduce stretches over hundreds of miles horizontally-but minute distances vertically. Says Silman, "I could throw a rock across the elevational range of many different species." These plants' preferred altitudes-and therefore the altitudes of the birds and other animals that feed on them, pollinate their flowers and disperse their seeds-are determined largely by temperature. And as the Andes heat up through global warming, these plants may be evicted from their natural ranges. Though there are no estimates of current warming in the Andes, all the tropical ice caps are in full retreat, and most are expected to disappear in the next 50 years.

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I head toward the cloud forest with six biologists and one field assistant. We plan to hike about 75 miles, gaining and losing 9,000 feet in elevation over passes approaching 13,000 feet. The first day we climb from the Rio Yavero west to the summit of an unnamed mountain in Peru's Manu National Park, one of the largest rainforest reserves on earth. Our goal is Callanga, a small valley in the heart of Manu. The initial pace of the hike has me breathing deeply, and I wonder if I will be able to keep up.

The Andes comprise high parallel ridges that follow the Pacific Coast of South America. In the north, these ridgelines can be moist on both sides, but in Peru, the western slopes are bone-dry and the eastern slopes are saturated by the mist and clouds from the Amazon Basin. On the drive from Cuzco to our trailhead, steep terraced farms covered the sides of these tall mountains like a mosaic. According to Silman, one of the leading causes of death of Andes farmers is falling off their land. In the canyons between ridgelines the forest are mostly pine and eucalyptus, both introduced species. Farmers going back even before the Incas have removed much of the natural vegetation. Only when you get to the ridgeline next to the Amazon Basin, where we do our hiking, do native species start to dominate.

On the first day we reach the Manu Park outpost, above the tree line, just before sundown. In the morning we fill up on oatmeal and start down the other side of the mountain. Trudging toward the trees, Silman points out that they are even farther down the mountain than they should be. For more than 6,000 years people have gathered firewood from this highest layer of vegetation and cleared the land for farming and grazing. The Incas, whose civilization flourished here in the fifteenth and sixteenth centuries, were masters of terraced farming. The polylepis tree, a member of the rose family once grew in dense groves up to 15,700 feet, 1,300 below the snow line, but disappeared about 5,000 years ago. Most trees are absent here and throughout much of the Peruvian tropical Andes at this elevation. Burning or harvesting trees is now prohibited in this national park, but enforcement on these steep, isolated slopes is difficult. "We should be walking in forest," says Silman, as we follow the muddy paths surrounded by low bunch grasses.

The trail descends into forest and clouds. In places the visibility is so poor that I can barely see the path in front of me. Everything drips. At 6,000 feet altitude, forests get up to 20 feet of moisture a year from rain. Water from the clouds may add another 5 to 20 feet. The moss, ferns, bromeliads and orchids that cover the tree limbs strip moisture directly from the clouds and hold it. At the same time, trees extend roots from their branches into these epiphytes, to get moisture and nutrients. The forest is a massive twisted tangle of roots, trees, and epiphytes, what Silman calls "stuff on top of stuff." The epiphytes act as a giant sponge. The water they collect feeds the plants and trees, all of which slow the flow of moisture as it makes its way downhill into the headwaters of the Amazon.

Scientists have described this type of forest as a nutrient-rich economy perched on a nutrient-poor substrate. The soils are acidic, cold, water-logged and nutrient poor. As a result, Silman has found, most plants put on less than a millimeter of girth a year-about the thickness of a dime. That slow growth rate doesn't portend well for the ability of cloud forests to respond to rapidly changing climatic conditions, says Silman.

We trudge down the soggy trail. At one point it opens into a wide bog covered with deep sphagnum moss. Silman takes a detour in search of a new plant, but suddenly his leg disappears into a sinkhole. He pulls it out, and backtracks to firmer ground. I stay on the trail. The biologists have their binoculars out frequently, to glimpse birds flitting by. Cloud forest is so dense that most wildlife encounters are brief. Still, the scientists spot colorful mountain tanagers, foliage gleaners, spine-tails, and ant pittas. The bird population goes up as we go down. The tropical Andes harbors 1,724 species of birds-more than double the number in Canada and the United States combined.

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Josh Rapp, a forest canopy biologist at Wake Forest, is the daredevil of our group. He uses a slingshot to shoot a small lead weight attached to fishing line over a high limb. He uses the fishing line to haul up stronger string, and the stronger string to haul up his climbing ropes. He secures the rope to the trunk of the 120-foot tree, dons his helmet, and inches up the rope. "There's just so much more variety, multiple layers, and varied structures up there than you get in a temperate forest," he says later. "And all this variety translates into some amazing habitats for epiphytes. There's big tank bromeliads shooting up red stocks with multiple yellow flowers and big clusters of pink orchids. It's incredible." The epiphytes may be particularly susceptible to climate change if the cloud level rises.

William Farfan, a biologist from the University of Cuzco, brings me a small orchid that is not much bigger than his thumb. "Look at that," he beams. "Isn't she beautiful." Indeed the tiny purple, yellow and ivory blossom is dazzling. Karina Garcia, also from the University of Cuzco, demonstrates her collecting prowess with a bunch of blossoms that trail to the ground like an enormous wild bridal bouquet. The Peruvians on our expedition compete with each other to capture the rarest and most elegant treasures from the forest; so far, she's ahead.

According to paleoecologist Mark Bush of the Florida Institute of Technology, who has worked extensively with Silman on these cloud forests, a prerequisite for understanding the ecology of tropical forest systems is "knowing what lives there." Thus collecting is a vital part of the scientific work here.

Work continues throughout the week. The biologists attach bands to trees to measure growth rates, collect specimens and stake out plots to monitor changes in the forest in response to climate change. We are not without visitors. A troop of wooly monkeys swings through the canopy, hanging onto limbs that seem barely able to hold their weight, and leaping across chasms. One morning Silman spots a pair of prehensile-tailed porcupines in the canopy that he says are even rarer than jaguars in this end of the world.

Many animals here have evolved close relationships to specific types of plants. In the dense, relatively windless cloud forest, birds and insects do most of the pollinating. Sword-billed hummingbirds, with bills longer than their bodies, feed only on flowers with long tubular blossoms. Sicklebill hummingbirds have a shorter bill with an almost 90 degree bend that fits only into similarly bent plants of the genus Heliconia. "There are more than 200 species of hummingbirds in the Andes," says Cristian Samper, director of the Smithsonian's National Museum of Natural History, "and every one of them has a story like that."

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In previous trips, Silman and Bush have hauled in, by mule and backpack, pontoon platforms that they float on lakes in the cloud forest. They lower a hollow drill from a miniature derrick into lake bottoms to gather 3-foot-long columns of sediment. These core samples are sent to Bush's lab in Melbourne, Florida for analysis. The data, which include the distribution of leaf skeletons and pollen, offers clues to how life in the region changed in response to the last Ice Age.

At Lake Consuelo, near the lower limit of the cloud forest, the researchers created a sedimentary record extending back 48,000 years. Comparing their data with different sediments analyzed by other scientists, Bush and Silman believe that during the last Ice Age, from about 105,000 to 11,000 years ago, when temperatures fell an average of 9 to 16 degrees Fahrenheit in this area, species moved down from the mountains into the Amazon Basin. "Basically the tropical forests had a much more benign climate for allowing species to survive," says Bush. "The lack of enormous ice sheets moving across the land, as happened in North America, prevented the wholesale extinctions that occurred in the north." As the earth then warmed about 19,000 years ago, species moved back up into the Andes-but at a very slow pace.

Based on that picture of the past, Silman and Bush think that these slow-growing cloud forests may not be able to keep up with this rapid climate change predicted for this century. It may require the trees to move totally outside their present ranges in just one or two generations. Scientists believe that most cloud forest species won't adapt in place to warmer climates, they'll have to move. Moving upslope will then require rapid adaptation to steeper slopes, different soils, different soil depths, and different microbial communities.

"Plants are going to have to migrate on average 2600 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 experts' predictions, the average temperatures in the cloud forest will increase by 4 to 5 degrees F.

Much of the information about the effect of changing climate on high-altitude forests doesn't come from the Andes, which have been little studied, but from Costa Rica. There, in the Monteverde cloud forest, the dry seasons have become longer since the mid-1970s, and these dry periods 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 last several decades has moved the cloud base in that part of Costa Rica TKfeet upward. If the movement continues, the clouds may rise above the crest of the Cordillera de Tilaran mountains, and the cloud forest will cease to exist.

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After working in the cloud forest above Callanga, the scientists return to camp. University of Cuzco Biologists Nati Raurau and Marlene Mamani press plant cuttings between sheets of newspaper while Luis Imunda, Silman's field assistant, makes dinner. The pressing continues into the night. Much of the load will be shipped to specialists in Peru and herbaria 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, even 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 Callanga valley, I've been staring up wearily at that 9,100-foot ascent. When Rapp and Silman announce their plan to do the climb and the 5,000 descent (a distance of 30 miles) in a single day starting at two in the morning, I decide to leave a day early, 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 it starts 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. Tito and Malta seem unaffected by the journey, but the mule and I have problems.

Our ascent travels the same upward path that the cloud forest may have to take.

When Silman and Rapp catch up with us the next day, their eyes are bleary. Silman says hello, then collapses spread-eagle on the ground. On the hills above we spot a farmer, attempting to burn the forest to make way for crops. "You can't stop them all," says Silman. Indeed, satellite photos taken over South America have shown up to 6,000 of these fires burning in tropical forest on a single night. Getting the world to slow down global warming may be an uphill battle, but this trip has taught me that uphill journeys are worth the effort.

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