Guided by biologists, volunteers briefly catch, band and release some of Delaware's visiting red knots each spring to monitor the health of the species. Maggie Starbard/NPR hide caption

A sign at the old Kerr-McGee uranium mill site in Grants, N.M., warns of radioactive material. This week, the Justice Department announced a $5 billion settlement against the mining company to pay for the cleanup of toxic sites the company left across the U.S. over a period of more than eight decades. Susan Montoya Bryan/AP hide caption

An oiled murre passes the darkened shoreline near Prince William Sound, Alaska, less than a month after the March 1989 spill. Erik Hill/Anchorage Daily News/MCT/Landov hide caption

Not all energy producers find fault with the EPA's rules. Calpine, which helped build the Delta Energy Center in Pittsburg, Calif., says the permitting regulations aren't overly cumbersome. JAKUB MOSUR/AP hide caption

Fishers are among the small carnivores threatened by rat poisons used to guard plants at illegal marijuana farms. John Jacobson/U.S Fish & Wildlife Service hide caption

A protest of the Keystone XL pipeline last March along its proposed route near Bradshaw, Nebraska. NH/AP hide caption

Al Jones of the West Virginia Department of General Services tests water as he flushes faucets and opens a rest room at the State Capitol in Charleston, W. Va., on Jan. 13, four days after a chemical spill into the Elk River. It wasn't until Jan. 21 that state officials were told by Freedom Industries that a second contaminant had also entered the river. Steve Helber/AP hide caption

A northern spotted owl in a Redwood forest. Michael Nichols/Getty Images/National Geographic Creative hide caption

The sea ice that polar bears use as a platform to catch seals is shrinking, threatening the species' existence. U.S. Fish and Wildlife Serivce/AP hide caption