Residents of Times Beach, Mo., were forced to leave their town in December 1982 because the chemical dioxin was found in the soil. Thirty years later, the Environmental Protection Agency can't decide how dangerous the chemical is. Bill Pierce/Time & Life Pictures/Getty Images hide caption

itoggle caption Bill Pierce/Time & Life Pictures/Getty Images

This young mountain yellow-legged frog, seen in San Bernardino County, Calif., is less than 1 1/2 inches long. Adults measure about 2 to 3 inches long. Scientists are trying to revive the frog population that has been decimated by drought, fire and diseases. USGS hide caption

itoggle caption USGS

Like this forest in Colorado, Whitebark Pines turn red when after being killed by the Mountain Pine Beetle. Jen Chase/AP. Jen Chase/AP/ASSOCIATED PRESS hide caption

itoggle caption Jen Chase/AP/ASSOCIATED PRESS

Many dead trees appear gray and red on the high-mountain slopes of Union Pass Bridger in Teton National Forest in Wyoming. W. W. Macfarlane hide caption

itoggle caption W. W. Macfarlane

Shell's Nanuq was built especially for oil spill response cleanup in the Arctic Ocean. It can store 12,000 barrels of recovered oil. The 300-foot vessel is docked at Dutch Harbor, Alaska, for the winter. Jeff Brady/NPR hide caption

itoggle caption Jeff Brady/NPR

Solar panels like these in England turn energy from the sun into electricity. But researchers are looking to capture the sun's energy to make liquid fuels for cars and trucks, by combining carbon dioxide, water and the chemical element cerium. Matt Cardy/Getty Images hide caption

itoggle caption Matt Cardy/Getty Images