A view from Iguana Island to mainland Venezula in the distance.
A view from Iguana Island to mainland Venezula in the distance.

Islands on the Brink

Although the scope of the research in Lake Guri is obviously quite large, my field work consisted, quite literally, of hugging trees.
January 31, 2002

Six of us are bunched together in a small blue boat, enjoying a cool breeze under the relentless Venezuelan sun. A maze of islands surrounds us, little green gumdrops whose reddish-brown shores slope steeply into forested interiors. Powered by a moody Yamaha motor, we chug our way toward Chiguire Island, a smidge of dry land named after the giant aquatic rodents that hang out there. As we draw closer, a ball of orange fur becomes visible at the top of one of the island's largest trees, a vigilant howler monkey not willing to share his space with other primates. This invasion of humans must be nothing short of terrifying to an animal that has lived most of its life peacefully on this little island retreat.

Our destination is just one of hundreds, maybe thousands, of islands in Lake Guri, a vast 4,300-kilometers-square hydroelectric compound in the largely uninhabited state of Bolivar, Venezuela. The most humbling statistic is that the lake is 1.6 times the size of Rhode Island, my home state. For two months this past summer, I joined a dozen or so scientists from around the world in calling this muddy oasis home. While we each had different research projects and organisms to study, we shared the goal of deciphering exactly what was going on in this system, a natural laboratory unlike any other in the world.

Lake Guri was formed artificially with the construction of the Raul Leoni Dam in 1968 and grew in size in 1986 when the second stage of dam construction was completed. Its purpose is to provide water-powered electricity to large regions of Venezuela. When the lake was enlarged in 1986, the flooding of the land formed an archipelago of green-studded islands that shed their former lives as hilltops. The remains of the trees are still visible in the "ghost forest," the chilling name given to the rings of dead trees that poke above water, their bases buried underwater some fifteen or twenty meters down like the lost city of Atlantis. A drought this summer left the water extremely low and revealed whole thickets of this ghost forest, creating magnificent graveyards of once-dominant trees now treading water. Their trunks are clumped so close together that navigating a boat between them requires ace piloting skills and, more often than not, the ability to duck and brace for collision.

Where most islands in the world were formed or separated from the mainland hundreds or thousands of years ago, these islands are a mere fifteen years old, making them ideal study sites. The plants and animals that survived the flooding are now confined to the borders of the islands, no longer able to roam the once-continuous land. This restriction on their movement has produced some unusual and ominous ecological phenomena that have been monitored by our research program for several years.

We ram our boat into the mud bank of Chiguire Island and claw our way up to its vegetated crown. The outer thickets resist our intrusion, but a few scratches later we penetrate to the interior. At just over half an acre, Chiguire is covered in trees both young and old. Save for some hardy leaves, the island is like a skeleton picked dry, a tangle of pale gray branches wrapped up by twisting vines.

John Terborgh, James B. Duke Professor of Environmental Science and leader of our group, says in his syncopated staccato voice, "Look at this God-forsaken place. And monkeys live here. It's amazing that anything can live here." The adroit veteran ecologist has thin, silvery hair pushed back straight from his long, tanned face, and a trim gray mustache. In his decades of working in the jungles of Peru and Venezuela, he seems to have found the fountain of youth. Agile and upbeat, Terborgh is often seen around camp wearing a tongue-in-cheek T-shirt that reads, "Thank God for Evolution," a gift from his graduate students at Princeton many moons ago.

 

A view from Iguana Island to mainland Venezula

Treehugger: The author and his subject.

Caught up in our exploration of the island, we forget about our howler-monkey host up above, who reminds us of his presence by attempting to air-drop yesterday's meal on our heads. Ken Feeley, a sandy-haired Duke graduate student and Terborgh apprentice, narrowly sidesteps the assault. Completely frustrated and baffled by our presence, the black-faced monkey resorts to that age-old means of escape--run, or frantically swing, as the case may be. In a few short, orange-blurred seconds, he darts through the trees, across a connecting land-bridge, and disappears into the safety of a neighboring island.

After ogling the jailbreak, the rest of us slowly turn our attention back to the trees, while Feeley stews over the implications of this event for his dissertation research. His project, an impressive web of hypotheses connecting everything from monkey dung to bird densities, relies in part on the idea that the monkeys do not move around between islands. This is normally a safe assumption, since they live in the trees and almost never come to the ground--except, that is, when a gang of bothersome biologists comes a-knocking.

The forest on Iguana Island is an imperfect tangle of life, a finger-painted canvas streaked with browns and greens, a ruddy masterpiece. A crispy carpet of leaves crunches under my feet with every step. The scene is awash in trees, some scattered large trunks, but mostly skinny trees and malleable lianas, spreading haphazardly in twists and turns, arched doorways, a gnarled mass, trip wires, monkey ladders, loops like swings, a dangling Y, an S, a C, intersections, overlaps, no beginnings, no endings. In the thicker parts, foliage blots out the sky above, so dense that you could tuck a pink school-bus beneath and never find it from the air. Among the leaves on the ground stands the occasional ant-hole, a small volcano of red dirt that spews fat-headed ants, hungry for the surrounding green in this world apart.

We leer, peer, and downright gawk at numerous trees, trying to identify them for Feeley's project. Here in the deep wild of Venezuela, there are no glossy field guides to consult, forcing scientists to rely on more unconventional, yet equally effective techniques. Approaching one particularly troublesome tree, Terborgh unveils a thick knife and shaves off a piece of bark. Leaning forward, he presses his face against the fresh white wound. Taking a deep breath of the tree's sweet smell, he concludes that it is Guatteria schomburgkiana, apparently not only part of the Annonaceae family, but also of the scratch-and-sniff family as well.

Hiking the short distance to the other end of the island, Terborgh again comments on the landscape around us: "Have you ever seen a place this trashed before? And humans didn't even do it. Usually it's bulldozers that do stuff like this, but this is ants and monkeys and other things." We don't usually think of an ant as the king of the jungle, but here on the small Lake Guri islands, this six-legged beast rules. In fact, it is mostly leaf-cutter ants that are responsible for the barren state of islands like Chiguire.

Here in Guri, the health of the island depends largely on its size. On larger islands and the mainland, a wide variety of predatory and large-sized animals thrive. Some are familiar, like the jaguar, puma, predatory birds, and wild cats, and others strange and unfamiliar, like the agouti, the tayra, the tapir, and the coati-mundi. But the smaller islands are unable to sustain these large-bodied animals.

Without vertebrate predators and seed-dispersing animals, the small islands have experienced population explosions of certain herbivores, creating a glut of lizards, rats, iguanas, and leaf-cutter ants. In addition, howler monkeys stranded on the small islands when the lake was created have lived on them predator-free for many years. This over-abundance of herbivores is having devastating effects on the island vegetation, stripping the trees bare. Such an avalanche of ecological dysfunction is called a "trophic cascade," or alternatively, Terborgh's more dramatic term, "ecological meltdown."

While the scope of the research in Lake Guri is obviously quite large, my field work consisted, quite literally, of hugging trees. Armed with a tape measure, some maps and a tool-belt, I worked on several islands measuring the diameter of adult trees that had been initially measured five years ago. The purpose of this work was to quantify scientifically the vegetation damage that was clearly visible all around us.

My mentor for this task was a garrulous Peruvian, Percy Nuñez, who works as a kind of freelance botanist, dabbling in eco-tourism here, writing field guides there. Known for his "hands of silk," he has a broad, padded face with wings of black hair that protrude from his baseball cap. Though he is nearly forty, his smile flashes a mouth full of braces. He speaks with a kind of wise serenity, and whenever I asked him a question, he rubbed his thick hand over his face, as if waking up the cells in his brain to think a little harder. Nuñez is one of the world's most knowledgeable tropical botanists, and has seen 10,000 different tree species in his career. He even has discovered and helped describe ten new species, including his favorite plant of all, Styrax nunezii (named for him).

Although the awkwardness of my last name may preclude the honor of ever having a species named after me--Balukjianii does not exactly roll off the tongue--I look forward to a career of discovery among the world of islands. I have been an "islephile" ever since the mullet-haired days of elementary school, when I pored over maps dotted with islands and declared that in my lifetime, I would visit every island in the world.

Islands have always captured people's imaginations, not only for their physical beauty but also for their symbolism as a secluded entity. Sir Thomas More saw water on all sides around him when he sketched out his vision of Utopia. And while poet John Donne declared that "no man is an island," we are time and again lured into the isolation afforded by islands' simple pleasures.

No matter where I drift, I hope never to stray far from the world of islands, those self-contained little worlds isolated from the smear of civilization. Island biogeography is my own self-designed curriculum, put together under the auspices of Duke's Program II, which provides students the opportunity to design an interdisciplinary curriculum without being limited to one of the conventional majors. That opportunity is what brought me to this team, and to Lake Guri.

Today's islands are often associated with white beaches and resort hotels; life on Lake Guri was not so glamorous. Our research team was divided between two camps, one on the large island Danto Machado and the other on Iguana Island, so tiny that John Elway could probably heave a football over half its length. The only permanent structure in either camp was a small shelter made of logs spaced far apart and held together by wire. A plastic tarp draped over the top of the shelter kept us dry during the torrential rains.

Words like "clean" take on a whole new meaning when you live in a tent for two months on an island where there is no running water, no electricity, no buildings, and, of course, no toilets. Food was simple, cooked over either a campfire or a gas stove, and inevitably consisted of some combination involving sauce and beans, rice or pasta. Every day after working in the field, we bathed in the murky lake water, jumping off trees in the ghost forest and withstanding the nibbles of little fish that enjoyed snacking on our bare bodies.

Scientists shuttled in and out of the camp over the course of the summer. They studied all sorts of things, from rats to land tortoises to the most pungent of all study organisms, dung beetles. Days were filled with collecting data on different islands, and nights were spent playing cards, writing, and chatting, while rowdy bugs flew into camp and pesky moths fluttered and flopped around as if someone had spiked their nectar. The whole while, life teemed around us--the horrid grunts of far-off howler monkeys in the distance and the screeching and squawking of parrots tearing through the air like squirrels in a china closet. The soft, continuous hum of hidden insects was occasionally interrupted by the whirling sound of a cicada, like an overcharged sprinkler.

A view from Iguana Island to mainland Venezula

One island's healthy forested interior.

Many of the processes and phenomena occurring on islands reflect those that occur on the mainland. But the isolation of islands has produced some pretty wacky results. Only certain intrepid species are able to colonize isolated islands (e.g., Hawaii), and once there they may remain separated from their native population for several generations. The isolation allows organisms to evolve into the outlandish and the bizarre, producing such fanciful creatures as Komodo dragons and the giant tortoises of the Galapagos. These are the island eye-catchers that any channel-surfer recognizes from brief flashes on the Discovery Channel. Although not as stunning, the leaf-cutter ants and howler monkeys of Lake Guri proved to be just as interesting.

The leaf-cutter ants are particularly effective in defoliating the small islands. While doing my field work one day, I saw a parade of leaf fragments dancing in a nice orderly line down the forest floor. An ant was underneath each leaf, clasping it tight with its mandibles. Ants stash great gobs of foliage in underground burrows and feed off of a fungus that grows on them.

Although things seem peachy for the ants and their vegetarian accomplices, the island trees will not be able to withstand this assault much longer. In the near future, we predict that a large number of tree species will go extinct on the islands (some already have), and that the only survivors will be snarling vines and inedible plants loaded with chemical and physical defenses. Without any more food, the ants, monkeys, and other herbivores are destined to crash, leaving the island a virtually empty wasteland.

At first glance, it might seem that while this obituary-to-be is a shame, it is at least confined to some obscure islands in the middle of nowhere in Venezuela. The bad news is that this same phenomenon is occurring all over the world. As our planet's natural habitats become increasingly fragmented because of human expansion and development, mainland landscapes are being chopped up into mosaics of "islands." Studying the Lake Guri islands is like looking into a crystal ball to see what looms for the rest of the world.

Balukjian is a senior from Greenville, Rhode Island.