Plankton make up 98 percent of the biomass of ocean life and provide half of the oxygen on the planet. Scientists are working to figure out how climate change may be affecting these important microorganisms.
M. Ormestad/Tara Oceans
Polar bears in the Beaufort Sea in northern Alaska. Scientist Charles Monnett caused a stir with a 2006 report on polar bears that were drowning, apparently owing to a lack of ice.
Steve Amstrup/Fish and Wildlife Service
In October 2010, a tiger walks past a vehicle carrying tourists at Ranthambore National Park in India. India's top court has banned tourism in parts of tiger reserves across the country in an effort to save the endangered big cat.
Researchers say that springtime snow is melting in the Arctic even faster than Arctic ice. That means less sunlight is reflected off the surface. Bare land absorbs more solar energy, which can contribute to rising temperatures on Earth. Above, a musher races along the Iditarod in the Alaskan tundra in 2007.