"Caves are home to some of the planet's most unusual creatures and important drinking water supplies. Now these underground resources are being polluted by surface activities, ranging from sewage spills to old factories. Experts call the problem 'extensive and serious.' Mammoth Cave National Park in Kentucky, Crevice Cave in Missouri and Whispering Canyon Cave in Alaska are examples. 'People need to be aware that there’s a subterranean ecosystem and that what happens on the surface impacts these unique ecosystems in a very real way,' said David Culver, a biologist at American University."