People in the Andes "lead vertical livelihoods," says Jeffrey Bury of the University of California at Santa Cruz. They take advantage of every ecological niche, growing crops in valleys and grazing llamas and alpacas on to bleak mountaintops. But farmers are being squeezed by warmer temperatures that shift crops up mountainsides and the expansion of mountaintop mining that destroys high wetland pastures, Bury says. Photo by Daisy Carlson Ref.  Scientific America