COSTA RICA: Paying the Price for Deforestation
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October 22, 2001
"It drips," said ecologist Robert Lawton in a Nature.com interview, describing the Costa Rican cloud forest, "and it's plastered with plants of all sizes climbing over each other. Stand still for long and they're growing on you." But the lush life he so colorfully describes may be threatened. Satellite pictures show that deforestation at the foot of western Costa Rican mountains is drying out swirling summit mists.
Warm, wet tradewinds blow off the Caribbean and are forced upwards by the mountains, cooling and condensing into a damp fog, which supports 4,572 square miles of forest at heights above 4,921 feet.
In places where agriculture has eroded lowland forests, the fluffy cumulus clouds that feed the peaks' forests no longer form, according to Lawton and his colleagues at the University of Alabama in Huntsville. Water evaporating between the trees normally lowers the air temperature. Without it, air is warmer and has to be lifted higher before it cools into mist. "It's extremely worrying," says conservationist Philip Bubb of the Tropical Montane Cloud Forest Initiative in Cambridge, UK. The findings may explain why the base of the cloud forest has begun to dry out, killing many species of frogs and toads.
If the forests are lost, unique plants and animals will die with them, as the peaks are isolated nests of biodiversity: "species of orchids might be found on only one mountain top," says Bubb. Cloud forests also channel clean, fresh drinking water to people in towns below. Tropical cloud forests on the mountain ranges of Central and South America, Africa and Asia could face a similar fate. Trees are being cleared quickly in these countries to make plantations and animal pasture. Most of lowland Costa Rica has already been cleared.
Lawton worked together with atmospheric scientists to photograph cumulus clouds across Costa Rica and nearby Nicaragua with the Landsat and Geostationary Environmental Satellite (GEOS). Atmospheric models confirm that clouds which form above a treeless landscape form at a greater height than those over forest.
Declining species and mist in the Costa Rican rainforest have been attributed in the past to climate change warming air over the sea, explains Alan Pounds of the Monteverde Cloud Forest Preserve and Tropical Science Center in Costa Rica. Deforestation complements this idea, Pounds believes. Removing a buffer of trees may exacerbate the effects of global warming.
The satellite findings indicate that conservation plans must now consider the entire landscape: "You can't create a series of parks and expect biodiversity to be preserved," says Pounds.