Meet Dr. Ellen Strong, a zoologist at the Smithsonian's National Museum of Natural History. Learn about the risks faced by snail populations in rapidly-changing freshwater ecosystems. Consider the ecological impacts of human activities such as damming and mining, which supply people with resources. Follow Ellen to freshwater streams around the U.S. as she studies vulnerable snail populations. See how Ellen discovers new species as she races to catalogue the biodiversity of freshwater snails, even as some species are faced with extinction.