Author and activist Bill McKibben paddles toward Follensby Pond in New York's Adirondack Mountains, along the route followed by Ralph Waldo Emerson in the summer of 1858. Julia Ferguson/NCPR hide caption

itoggle caption Julia Ferguson/NCPR

A helicopter flies near the Lake Fire in California's San Bernardino National Forest on June 19. Firefighters mobilized to combat the wildfire from the air, but they had to be grounded to avoid drones in the area. David McNew/Reuters/Landov hide caption

itoggle caption David McNew/Reuters/Landov

Many homes in the mountains of Kittitas County, Wash., are at severe risk for a wildfire. Fire managers are worried that parts of typically "wet" Washington state are years behind other places in the West when it comes to fire mitigation and prevention. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR
Stephen Buchmann/Scribner

"Our degree of oil dependency is our degree of vulnerability."--Rob Hopkins James Duncan Davidson/TED hide caption

itoggle caption James Duncan Davidson/TED

"We've under-priced water, we've over-exploited it, we don't regulate how people pump groundwater out of the ground.... we just use too much."--Jonathan Foley Courtesy of TEDxTC hide caption

itoggle caption Courtesy of TEDxTC

"There's a saying in Suriname that I dearly love: 'The rainforests hold answers to questions we have yet to ask.' But as you all know, it's rapidly disappearing."--Mark Plotkin Ryan Lash/TED hide caption

itoggle caption Ryan Lash/TED