Marina Silva, shown here in Rio de Janeiro on Wednesday, is tied in polls with incumbent President Dilma Rousseff. Silva, the candidate for Brazil's Socialist Party, says if elected next month, she would be "the first social environmentalist president." Silvia Izquierdo/AP hide caption

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James Cameron talks about how his fascination with the world around him has driven his film career. James Duncan Davidson/TED/Courtesy of TED hide caption

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"The State of the Birds" 2014 report found that red knots (above) and other shorebirds are among the most threatened groups in the U.S. More than half of U.S. shorebird species are on the report's Watch List — species that are currently endangered or at risk. Gerrit Vyn/The Smithsonian Institution hide caption

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A Baltimore oriole perches near apple blossoms in Mendota Heights, Minn. Universal Images Group via Getty Images hide caption

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Opponents of Michigan fish farms say there is no room for them in the lakes because of sport fishing and other recreational activities. sfgamchick/Flickr hide caption

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Off the coast of Southern California, a crowd watches a blue whale rise to the surface earlier this summer. A new study says the population of blue whales off the West Coast is close to historic levels. Nick Ut/AP hide caption

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Chicks in the Perdue hatchery in Salisbury, Md. The company says an increasing number of its chickens are now raised using "no antibiotics, ever." Dan Charles/NPR hide caption

itoggle caption Dan Charles/NPR