The Amazon's "flying rivers"—humid air currents that deliver water to the vast rain forest—may be ebbing, which could have dire consequences for the region's ability to help curb global warming, an expert said this week at the Copenhagen climate conference.

Rising temperatures in the Amazon region, in large part due to climate change, are creating more arid savannas, which disrupt the water cycle vital to Brazil's farming and energy industries.

Deforestation also plays a role. As more of Brazil's rain forests fall to logging and agriculture, there are fewer trees to release the water vapor that creates these flying rivers.

Until recently, Amazon forest loss has been primarily linked to the trees' role in trapping greenhouse gases, such as carbon