Magazine article International Wildlife

CASE OF THE DWINDLING CLOUD FOREST - Something Is Amiss in Costa Rica's Famous Fogged-In Hilltops, and Global Climate Change May Be the Cause

Magazine article International Wildlife

CASE OF THE DWINDLING CLOUD FOREST - Something Is Amiss in Costa Rica's Famous Fogged-In Hilltops, and Global Climate Change May Be the Cause

Article excerpt

Naturalist Michael Fogden had lived in the cloud forest of Monteverde, Costa Rica, for nearly 15 years before he began to realize that gradually, subtly, the forest was changing. The signs were easy to overlook: Even at the height of the winter dry season, clouds still settled among the trees in this narrow zone of wet forest that straddles the spine of a mountain range 5,000 feet above sea level. Orchids, mosses and bromeliads still festooned the branches of the mist-shrouded trees, and every leaf and frond dripped with moisture. But for those who knew where to look, the signs were there. Many of the water-loving frogs that used to fill the forest had vanished. And as new species crept into the area, the fauna of Monteverde had grown to look more and more like that of drier habitats lower on the mountainside.

Through painstaking detective work, Fogden and an unlikely group of colleagues-including biologists, climatologists and even an astrophysicist-may have discovered what's behind these changes. Their findings indicate that as global climate change warms the nearby ocean, the cloud layer that gives the forest its name visits less and less often, especially at lower altitudes, leaving the flora and fauna thirsting for its life-giving mists. If they're right, the cloud forests of Central America could be among the first entire ecosystems to fall casualty to global warming.

Fogden didn't set out to study global climate change. An Oxford-trained ornithologist, he had walked away from his university career in the late 1970s so that he and his wife, Patricia, could start a new life as natural history photographers and writers. They settled in Monteverde, Costa Rica, a small community in the cloud forest. "We've become tropical derelicts," Fogden jokes. But old habits die hard, and he began keeping count of the birds of the forest year after year.

By the early 1990s, he was noticing that blue-crowned motmots, brown jays, golden-crowned warblers and other birds of drier, lower-elevation rain forests had begun nesting in his study area. He had even seen keel-billed toucans, also from lower elevations, breeding side-by-side with the symbol of the cloud forest, the resplendent quetzal. In all, Fogden's notes meticulously document the arrival and breeding of 15 new bird species from downslope, plus others that have moved in but have not yet begun to breed-a rate of nearly two new invaders per year.

Most of the original cloud forest birds are still there, too, though a few high-elevation species that once were common, such as the fiery- throated hummingbird, the collared redstart and the ruddy treerunner, now show up rarely if at all. But Fogden expects a lot more species to vanish from his study area in the years to come. "Most cloud forest birds are long-lived and territorial," he explains. "It's easier to stick to their territory even though it's not as good as it used to be." But when the current occupant dies, no other member of its species may be willing to occupy a territory that's no longer high-quality cloud forest.

Nor are birds the only ones following such patterns. One lowland squirrel species, for example, had never been seen in Fogden's study area until 10 years ago, only in drier, lower parts of Monteverde. Now, people see the squirrels every day in the study area. The same is true for the brilliant blue morpho butterflies. "They were very rare when we first arrived," says Fogden. "Now you can see them any sunny day."

Meanwhile, Fogden's neighbor Alan Pounds, an ecologist and long-time Monteverde resident affiliated with the Monteverde Cloud Forest Preserve, had his eye on another problem. In 1987 alone, 20 of 50 frog species had vanished from his study area near Monteverde, and other extinction episodes came in 1994 and 1997. Most of the missing species have not returned. "If you walk through the forest, you don't see any frogs. You used to see lots," says Pounds. …

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