The Last Frontier

摘要

Since the Conservancy first hired Lewis four years ago to survey Tennessee caves, he's explored dozens like, this one, which lies in central Tennessee's Sequatchie Valley, on the Cumberland Plateau. Lewis is a throwback to the naturalists of yesteryear, who combed frontier wilderness and found new species almost everywhere they looked. In their 1804 journey up the Missouri River, 19th-century naturalists Meriwether Lewis and William Clark observed and reported on 122 animal species and subspecies newto science, including the grizzly bear, California condor and black-footed ferret. But the continent's wild places have mostly been tamed, its wild species already tallied. Only two new bird species, for example, were discovered in the United States during the entire 20th century.