Bike sharing is all the rage in Europe. Now, Washington D.C., Chicago and San Francisco are among a handful of cities implementing bike-sharing programs in an effort to tackle traffic problems, reduce greenhouse gas emissions and boost eco-cachet. Learn more about bike sharing, and watch a video about one of the first bike sharing programs in North America.

In a major report published Friday, the World Wildlife Fund (WWF) says that Earth’s wildlife populations have plummeted by about 25 percent overall since the 1970s, despite increased awareness about …

During the past century, the rhinos of Africa and Asia have been pushed out of their habitats and hunted nearly to extinction for their horns, which are believed — erroneously — to possess healing properties.

In Zimbabwe, the number of endangered rhinos killed by poachers has increased dramatically over the last few years. Since 2000, an estimated 72 black rhinos have been shot in the southeastern part of the country. Compare that figure to the years between 1993 and 2000, when not one black rhino was poached in the area. Why the sudden increase?

Jason Margolis travels with producer Loren Mendell to the heart of rural Mexico to discover how a former schoolteacher, Pati Ruiz Corzo, is using carbon trading to preserve the Sierra Gorda Biosphere and revitalize a region.