Call of the Wild

We speak to a Latino activist about why most of the visitors to US national parks are white and how that is not good for the future of the parks. We visit the largest naval base in the world, which is threatened by rising sea levels. Next, we visit the American south-west where some have to travel 20 miles for clean water.

Also, we search for what may be the world's most valuable fish, go undercover to find out where our old electronics end up, and overhear a group of Andean women sing in the back of an Inca temple on Machu Picchu.

(Photo: Tourists watch the The Old Faithful geyser at the Yellowstone National Park in Wyoming. Credit: Mark Ralston/AFP/Getty Images)