The Foamy Rio Tietê

Ecologist Greg Asner chases droughts, measuring the effects using 3-D maps. All over the Western Amazon, he's seeing huge loss in tree canopy. The mega-droughts in Brazil are damaging the rivers that fly above the forest and causing problems elsewhere. Because of the drought, there was not enough water to flush pollutants, like this toxic foam, out of the Rio Tietê.