The Silence of Amazonian Forest Fragments

Original article written in 2007

Looking down on the Brazilian Amazon, photo by Jake Kheel

“When we started the project, all of this was rainforest” observes our host Tom Lovejoy, eminent conservation biologist and environmental problem-solver. We have been skidding along a slick clay road, surrounded by dense tropical rainforest for the last hour and a half, when suddenly we emerge into a brightly lit pasture littered with grazing ghost white cows, who occasionally look up uninterestedly at our caravan of rickety trucks. The change from forest to pasture is jarring. The forest is cool and dank and we are accompanied by the sound of macaws, toucans, and parrots flying overhead. The pasture is dry and desolate and the fields are virtually silent. “Once they cleared the forest, they planted all of the grass by hand, tuft by tuft, like hair plugs.”

Tom Lovejoy the creator of the Biological Dynamics of Forests Fragments Project, photo by Jake Kheel

The project Lovejoy refers to is the “Biological Dynamics of Forest Fragments,” the largest and longest running ecological experiment in the world. He conceived of the experiment in 1979 to lend clarity to a fierce, scientific debate known simply as “SLOSS: Single Large or Several Small.” The debate originates with the realization that before long, nearly all of the world’s remaining wilderness will be carved up or shrunk into fragments or “islands” of habitat. This sobering thought forces scientists and resource managers to make difficult decisions about which islands to invest in and protect in order to preserve habitat for wild plants and animals. The SLOSS debate comes down to whether conservationists should prioritize islands of habitat that are as big as possible, or whether many small, isolated patches are preferable in order to hedge against potential disasters in the single fragments and accommodate more specialized organisms.

With the protection of nature already a chronically underfunded endeavor, the allocation of these already limited resources is not trivial. As program director for World Wildlife Fund in 1973, Lovejoy was in the position of making decisions about the design of nature reserves and the question of SLOSS was basic to his work. “I used to worry about it a lot, and discuss it with my scientific colleagues.”

Bumping along the clay-lined roads of the Amazon, photo by Jake Kheel

If a nature reserve becomes isolated from similar habitat, or contains insufficient area to support the needs of the organisms that reside there, over time “ecosystem decay” takes place, where gradually the ability of organisms to survive in that particular island of nature diminishes, leading to an ecosystem that is protected yet biologically impoverished. As the islands of habitat become more isolated from similar habitat, for example when a forest is surrounded by highways or cornfields, the patch of forest will lose its original richness and diversity, and even organisms that are protected on paper may be doomed to extinction.

“I always suspected that the answer would be large reserves. But at that time we lacked sufficient data.” While the debating camps shouted each other down in scientific journals and conferences, a “brilliantly simple” idea occurred to Lovejoy. In Brazil in the late 70’s, where he had spent the early part of his career studying birds, laws gave incentives to clear Amazonian rainforest for more “productive” purposes such as timber or cattle, however landowners were required to leave 50% of the land as intact forest. Seeing opportunity where most environmentalists saw only tragedy, Lovejoy convinced first Brazilian government officials, then cattle ranchers to carefully plan the clearing of forests, creating isolated “islands” of differing sizes with the government mandated patches of remaining forest. The fragments, divided into 1, 10, and 100 hectare plots, would simulate the reaction of forests ecosystems to fragmentation and provide conservationists with important clues about the best approach to designing nature reserves. Lovejoy then recruited teams of local and international scientists and researchers to carefully document the forest fragments and their inhabitants before, during, and after isolation.

The Rainforest Machine, photo by Jake Kheel

“The value of the project grows in time,” says Lovejoy, like a proud father. Now in its 29th year, the project has been as scientifically productive as it has been influential to conservation. The project has trained hundreds of American and Latin American scientists and researchers and a cadre of Brazilian government officials, resource managers, and conservationists, armed with deeper understanding of the complex dynamics of the Amazon rainforest and tools to protect it. The project has also churned out close to 500 peer reviewed papers, articles, and books, and been the subject of over 100 graduate theses. Turning conventional understanding of studying nature on its head, the Forest Fragments project allows students and researchers to study the complex web of life of the rainforest, and equally important the profound impact humans are having on it.

As for SLOSS, the project produced some predictable and some surprising results, but all told the experiment has shown that bigger is clearly better. In the experiment, predictably, larger mammals such as jaguars and monkeys that require expansive ranges quickly disappeared. More adaptable species of plants, birds and insects increased in the fragments. Animals and plants that don’t require a lot of room could survive in the interiors of the larger fragments where conditions stayed relatively unchanged and disappeared in areas where they did. Plants requiring the help of other organisms also suffered as the pollinators they depended disappeared, particularly from the smaller fragments.

The view from inside Camp 41, photo by Jake Kheel

But some results were less intuitive, such as the disappearance of a significant number of large trees, particular along the edge of forests and proportionately more in the smaller fragments. In contiguous rainforest, the dense forest canopy, created primarily by the big trees, keeps most of the intense equatorial sunlight from reaching the forest floor. As a result the understory is mostly shaded, moist and protected from wind. Fragmentation creates new edges to the forest and exposes trees on the edge of forests to more intense sunlight, wind and heat. We could see this as you drove through the forest fragments project.

The changes in environmental conditions and especially the increased exposure to wind took down the big trees relatively quickly. This drastically altered the complex forest architecture that ultimately had a cascade impact on the complexion of all the species that occupy the forest. “When you walk around the smaller fragments, you can feel, and even hear the dryness of the material on the ground,” observed Lovejoy, as he leads us along one of the forest fragment edges. “The difference between the fragments and contiguous forest is obvious.” Where scientists had long suspected the potential for “ecosystem decay,” in the Amazon they had quantifiable data demonstrating it.

Possibly the most important contribution to the SLOSS debate was the fact that even the biggest 100-hectare fragments were not big enough. In a defining study using accumulated data from the project, researchers found that 50% of all forest-dwelling bird species disappeared within 10-15 years in the larger fragments, and even faster in the smaller patches. In the 1980’s, extrapolating on some of the ideas of the fragments project, William Newark found that in American national parks, in 42 instances over the last 100 years, mammal species have gone locally extinct after the founding of the park, without taking into account direct human interference such as hunting. Ecosystem decay seems confirmed and the role of the size of the reserves is undeniable. Recent work suggests that the minimum critical size of nature reserves is in the neighborhood of 1,000 hectares, or ten times the size of the largest fragments in the experiment.

The trails of Camp 41, photo by Jake Kheel

Shortly before dawn, our group follows Portuguese ornithologist Gonçalo Ferraz through wholly intact rainforest, along trail “B4” in a grid of pathways carved into quadrants, a network of trails obviously designed by the enterprising mind of a scientist. This forest is “probably one of the largest stretches of intact rainforest in the Amazon, extending all the way to the Atlantic Ocean.” The birds are just waking up and the sounds of the forest are continuous. We are accompanied by the screech of the screaming piha (Lipaugus vociferans), the gurgling “gulup” sound of the Mott-mott (Momotus momota), and the harmonic songs of the Musician Wren (Cyphorhinus arada) that calls back to Ferraz’s whistling. Occasionally an iridescent Blue Morpho butterfly (Morpho achilles) flits by. The trees come alive as a group of Saki monkeys crash through the canopy overhead, following the lead monkeys’ imaginary trail through the trees. Ferraz explains how certain groups of distinct bird species hunt together through the forest understory in “mixed species flocks,” a phenomena that provides strength in numbers without the competition for food. When we surprise a Gray winged trumpeter (Psophia crepitans) and it takes off hurtling off in the brush ahead of us.

Though the SLOSS debate has quieted, in no small measure due to the mediation skills of Lovejoy and the results of the Forest Fragments project, the ongoing threat to the rainforest has not. Now the President of the Heinz Center for Science, Economics, and the Environment, Lovejoy is no less dedicated to the Amazon, though the emphasis of his argument has shifted to a more systematic, global perspective of the importance of rainforest protection. Recently he has taken to peppering the editorial pages of prominent Brazilian and International journals with pleas to protect the “Rainforest Machine” of the Amazon for the benefit of the global climate and the economies of a large portion of South America countries.

Scientists have known for over 20 years that the Amazon acts as a giant self sustaining “Rain machine,” taking ocean moisture headed towards the Andes and cycling it through its massive tangle of vegetation, producing over 50% of its own rain. New studies fear that continued deforestation of the rainforest could lead us to a “tipping point” at some unknown moment in time, disturbing the hydrological machinery of the rainforest, causing untold harm to Brazilian and numerous South American country economies that depend on this water farther downstream for industrial agriculture crops and hydro-electric generation. Ironically, the industrial agriculture that serves as a primary threat to the rainforest is entirely dependent on the water it produces. While trying to encourage economic growth through development of the Amazon, the Brazilian government may be guaranteeing its own economic demise.

Despite the somewhat astonishing fact that close to 40% of the Brazilian Amazon falls under some category of legal and effective protection, despite near constant pressure to clear and develop it for different activities such as timber, cattle and more recently settlements for the Manaus Free Zone, research suggests that the “tipping point” of deforestation for the breakdown of the Rainforest Machine may be around 40%.  However, when potential drought events such as El Nino and the Atlantic drought of 2005 are considered, that tipping point of deforestation may be closer to 20%. Remote sensing analysis estimates that already in Brazil alone about 17% of the rainforest has been cleared, not to mention lesser-known rates of deforestation in other Amazonian countries. We may be dangerously close to the tipping point already.

Lovejoy, while still concerned about the birds, butterflies, and monkeys of the rainforest, talks a lot more these days about protecting the Brazilian economy and avoiding deforestation for the equilibrium of the global climate. Roughly one-fifth of the annual increase in greenhouse gases concentrations in the atmosphere comes from deforestation, making Brazil one of the top half dozen emitters in the world. “The great forest nations” as Lovejoy refers to them, should be compensated for “keeping carbon in forests and out of the atmosphere,” and he keeps quite busy developing international strategies and cajoling politicians, decision-makers, and countries to do this.

On our last dawn with Lovejoy, we climb a rusting research tower before first light, and stand perched on a platform 120 feet high, looking down on the lush carpet of rain forest below. As the sun comes up, the sound of water is palpable. A fog rises up from the distant tree line, then can be heard dripping down on the leaves below and all around us, without ever raining, and then turns back into fog. As it gets lighter, birds criss-cross in front us on the tower, howler monkeys engage in heated arguments echoing in the distance, but throughout the sound of water moving and changing forms is unmistakable. “That’s the sound of the Rainforest Machine,” says Lovejoy cheerfully. We can only hope that we are not unknowingly running our own ecological experiment on it.

Your truly in 2007

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