Fragments of the forest

Natural History, July-August, 1998 by William F. Laurence

To Portuguese explorers of the sixteenth century, the rainforest of the Amazon was a vast, verdant hell. But they pressed forward eagerly in search of gold and rare woods, while missionaries looked for heathen souls for conversion to Christianity. Soon after Europeans claimed the land, they established plantations and enslaved thousands of Indians to work them.

Historically, the Amazonian rainforest remained nearly intact because of its sheer size, its soils that were unsuitable for agriculture, and the deterrent of such endemic diseases as malaria and yellow fever. Recently, however, the tide has turned against one of the last great forested areas remaining in a largely deforested world. In the Brazilian Amazon, annual forest loss from all causes rose from less than 3 million acres in 1991 to an average of 4.8 million acres during each of the past three years--the equivalent of seven football fields a minute. In 1995 alone, more than 7 million acres were destroyed--an area roughly the size of Belgium.

Using chain saws and bulldozers, industrial loggers go after such valuable timber trees as mahogany, but they also kill many other kinds of trees in the process. In logged areas, up to half of the protective canopy is destroyed, drying out the remaining forest and increasing the likelihood of fires. Loggers also create roads, opening up forest tracts for settlers who clear plots for farming or cattle raising, and for hunters who slaughter peccaries, tapirs, monkeys, and jaguars.

Companies from Malaysia, Indonesia, China, South Korea, and Singapore are stripping the Amazon's most valuable timber in record time. Their major customers are the United States, Europe, and Japan. In 1996 alone, Asian companies invested more than half a billion dollars in the Brazilian timber industry, and they now own or control more than 30 million acres of rainforest in Brazil, Suriname, and Guyana. Until recently, major deforestation was concentrated along the southeastern arc of the Amazon--in the Brazilian states of Acre, Rondonia, Mato Grosso, and Park, as well as in Bolivia.

But now new roads have been cut into the heart of the Amazon Basin, providing access to areas once considered too remote for development. One such highway runs from the city of Manaus, in the central Amazon, 600 miles north to the Venezuelan border. Last year, Brazilian president Fernand0 Cardoso announced that approximately 15 million acres of forest along the highway would be opened to settlement, creating a farming area "so colossal that it would double the nation's agricultural production." Large expanses of forest have al ready been cleared along fifty miles of the new road.

With a burgeoning population that now exceeds 1.5 million, Manaus is the hub of development in the Amazon. Home to the infamous "rubber barons" at the turn of the century, Manaus was, for a few brief decades, one of the world's wealthiest cities, where legendary high-rollers flaunted their wealth by lighting cigars with paper currency and sending their soiled laundry to Europe. A grand opera house still stands as a testament to its past opulence. The rubber boom that fueled the city's rise collapsed long ago, but today, money and people are again pouring into the city as tropical timber is converted into cold cash.

Logged and fragmented forests--and the scrubby regrowth that colonizes unused fields and pastures--are rat more prone to fires man are intact rainforests. And since the traditional method of clearing land is to hack down vegetation and then burn what remains, the danger is ever present that farmers' fires will rage out of control--especially in drought years. According to archaeologists who have studied charcoal deposits in Amazonian soils, four catastrophic fires during the past 2,000 years coincided with droughts caused by El Nino. Now, even minor droughts have catastrophic potential. In the first three months of 1998, in the northern Brazilian state of Roraima, fires lit by farmers and ranchers swept through more than 2 million acres of savanna and deciduous forest. In Manaus, the smoke from fires lit in local forests became so severe that the airport was temporarily closed and hospitals reported a 40 percent rise in the incidence of respiratory problems.

Decades ago, when ecologists and other life scientists realized that this kind of development would inevitably reduce and fragment the Amazonian forest, they began to wonder if any plants and animals could withstand such an onslaught. If reserves were to be set aside, how large would they need to be to ensure the survival of rainforest species into the next century?

With such questions in mind, ornithologist Thomas Lovejoy initiated the Minimum Critical Size of Ecosystems Project in 1979. (Some years later, it was renamed the Biological Dynamics of Forest Fragments Project.) Lovejoy was soon joined by fellow ornithologist Richard Bierregaard and several Brazilian colleagues in what was to become one of the world's longest-running ecological experiments. Their efforts were facilitated by a Brazilian law stipulating that 50 percent of the land in any Amazonian development project must be retained as uncut forest. After learning that four experimental cattle ranches were to be sponsored by the Brazilian government near Manaus, Lovejoy proposed that the ranchers divide the required portion of uncut forest into isolated patches of various sizes, ranging from 2.5 to 25,000 acres. Researchers could then study the communities of trees, birds, mammals, frogs, butterflies, and other animals in the areas, both before and after creation of the patches, to learn how each was affected by fragmentation.