Brazilian river dwellers ferry açaí berries to a market in the Amazon's northern estuary. The antioxidant-rich palm fruit, grown throughout the Amazon, has become a global superstar—a ''Cinderella fruit,'' in the words of Amazon expert Nigel Smith.

A multimillion-dollar export, açaí is found in juices, smoothies, and energy bars. But some conservationists fear skyrocketing demand for this super-berry could hurt Amazon forests. Others note planting açaí along the river protects against slash-and-burn farming.