Callery pear trees in Pittsburgh. The smell of the invasive trees has been compared to rotting fish and other stinky things. Luke H. Gordon/Flickr hide caption

itoggle caption Luke H. Gordon/Flickr

Austin Holland, research seismologist at the Oklahoma Geological Survey, gestures to a chart of Oklahoma earthquakes in June 2014 as he talks about recent earthquake activity at his offices at the University of Oklahoma in Norman, Okla. The state had three times as many earthquakes as California last year. Sue Ogrocki/AP hide caption

itoggle caption Sue Ogrocki/AP

A cherry tree and its blossoms are covered with snow in an orchard near Traverse City, Mich. Three years ago, almost every fruit crop in Michigan was frozen out when cold temperatures followed some 80 degree days in March. John L. Russell/AP hide caption

itoggle caption John L. Russell/AP

"Part of the reason we're here is because climate change is threatening this treasure and the communities that depend on it," Obama said Wednesday of his visit to Everglades National Park in Florida. "If we don't act, there may not be an Everglades as we know it." Mandel Ngan/AFP/Getty Images hide caption

itoggle caption Mandel Ngan/AFP/Getty Images