Channel-billed toucans are important seed dispersers in rain forests. Courtesy of Lindolfo Souto/AAAS/Science hide caption

itoggle caption Courtesy of Lindolfo Souto/AAAS/Science

Colonists built the original glass-blowing kiln in Jamestown, Va., at this beach for easy access to the sand. Now the site is just inches above the water level. John W. Poole/NPR hide caption

itoggle caption John W. Poole/NPR

The four cuts at the top of this skull "are clear chops to the forehead," says Smithsonian forensic anthropologist Douglas Owsley. Based on forensic evidence, researchers think the blows were made after the person died. Donald E. Hurlbert/Smithsonian hide caption

itoggle caption Donald E. Hurlbert/Smithsonian

Doctors at a hospital in Aleppo, Syria, treat a boy injured in what the government said was a chemical weapons attack on March 19. Syria's government and rebels accused each other of firing a rocket loaded with chemical agents outside of Aleppo. George Ourfalian/Reuters/Landov hide caption

itoggle caption George Ourfalian/Reuters/Landov

Wind turbines at the San Gorgonio Pass Wind Farm in Whitewater, Calif., in 2012. Bloomberg via Getty Images hide caption

itoggle caption Bloomberg via Getty Images

Thousands of "fairy circles" dot the landscape of the NamibRand Nature Reserve in Namibia. Why these barren circles appear in grassland areas has puzzled scientists for years. N. Juergens/AAAS/Science hide caption

itoggle caption N. Juergens/AAAS/Science

This photo from a Kyodo News helicopter shows a flame of natural gas from a Japanese deep-sea drilling ship on Tuesday. This successful extraction of methane from the seafloor was a world first. Kyodo/Landov hide caption

itoggle caption Kyodo/Landov

Scientists say they have put together a record of global temperatures dating back to the end of the last ice age, about 11,000 years ago. This historical artwork of the last ice age was made by Swiss geologist and naturalist Oswald Heer. Oswald Heer/Science Source hide caption

itoggle caption Oswald Heer/Science Source

In this Sept. 1, 2008, photo released by Wildlife Conservation Society, a male forest elephant strides across Langoue Bai, Gabon. Elizabeth M. Rogers/Wildlife Conservation Society via AP hide caption

itoggle caption Elizabeth M. Rogers/Wildlife Conservation Society via AP

American Electric Power's natural gas-burning plant in Dresden, Ohio, is one of the energy company's new investments in alternatives to coal-burning plants. Michael Williamson/The Washington Post/Getty Images hide caption

itoggle caption Michael Williamson/The Washington Post/Getty Images

The Boston Tea Party museum sits right on the edge of the harbor. With rising sea levels and the increasing threat of strong storms, buildings like these are at particular risk of flooding. Christopher Joyce/NPR hide caption

itoggle caption Christopher Joyce/NPR

Plosky Tolbachnik volcano erupts in Russia's Far Eastern Kamchatka Peninsula on Jan. 6, 2013. It's not a so-called "super volcano," but every million years or so scientists say the Earth burps up volcanoes that can erupt for thousands of years. Alexander Petrov/AP hide caption

itoggle caption Alexander Petrov/AP