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Amazon Rain ForestWorkers clear a road through Brazil's Amazon rain forest—one of the world's ten most threatened forests, according to an international conservation group.This weekend, people around the world will plant trees in their neighborhoods as part of Earth Day celebrations. (See pictures of quirky Earth Day stunts.)But Earth Day efforts won't be enough to replace the trees in forests like the Amazon, which are disappearing due to human activities, said Richard Donovan, vice president of sustainable forestry at A Rainforest Alliance."We're very supportive of tree planting, but tree planting by itself is not enough—we need to conserve forests, not just trees," Donovan said.(Explore an interactive map of the embattled Amazon in National Geographic magazine.)While the rate of Amazon deforestation has slowed somewhat in recent decades, it's still among the highest of any forest in the world, he said.Large tracts are being cleared annually to make way for cattle ranches and cash crops such as soy beans and, more recently, palm oil.Another concern are the growing number of roads through the rain forest, which are aiding loggers and serving as entry points for everyone from farmers and developers to oil and mineral prospectors.—Ker Than

Photograph by Bruce Dale, National Geographic