Polar bear at the Arctic. Original from NASA. Digitally enhanced by rawpixel. Free Image from public domain license 
Sand dunes in Southern California. Original image from Carol M. Highsmith’s America, Library of Congress collection.… Free Image from public domain license 
Brown pelicans search for fish in brackish water at NASA's Kennedy Space Center in Florida around dawn. Original from NASA .… Free Image from public domain license 
Along the southeastern coast of Greenland, an intricate network of fjords funnels glacial ice to the Atlantic Ocean. Original… Free Image from public domain license