The city of Gladstone near the Great Barrier Reef is the world's fourth largest coal-export hub. Dredges, like one seen here, have turned the harbor brown as they work to expand the coal port. Richard Harris/NPR hide caption

itoggle caption Richard Harris/NPR

Ken Caldeira of the Carnegie Institution for Science takes a water sample during his experiment out on part of the Great Barrier Reef. The water is slightly pink because his team is using a dye to trace an acid-neutralizing chemical as it flows across the reef. Richard Harris/NPR hide caption

itoggle caption Richard Harris/NPR

On Australia's Heron Island, buff-banded rails like this one have become the avian equivalent of a weed. Richard Harris/NPR hide caption

itoggle caption Richard Harris/NPR

Heron Island is located on the southern end of the Great Barrier Reef, about 25 miles off the northeast coast of Australia. Ted Mead/Getty Images hide caption

itoggle caption Ted Mead/Getty Images

Perch exposed to the anxiety drug oxazepam were more daring and ate more quickly than fish that lived in drug-free water. Courtesy of Bent Christensen hide caption

itoggle caption Courtesy of Bent Christensen

An official with the Korea Meteorological Administration shows a seismic image of a tremor caused by North Korea's nuclear test, in Seoul on Tuesday. Kim Jae-Hwan/AFP/Getty Images hide caption

itoggle caption Kim Jae-Hwan/AFP/Getty Images

Vegetation like the kind growing here at Michigan State University's Kellogg Biological Station could one day be used to feed small biofuel refineries spread throughout the Midwest. J.E.Doll/Michigan State University hide caption

itoggle caption J.E.Doll/Michigan State University