With many national parks across the country in trouble from such myriad threats as climate change, overcrowding, energy exploration, invasive species, and poor air quality, National Parks Traveler’s  new “Threatened and Endangered Parks” lists identify parks that are struggling to retain the very essence that led to their inclusion in the National Park System in the first place. In this week's show, Phil Francis of the Coalition to Protect America's National Parks and Mark Wenzler from the National Parks Conservation Association discuss the threats facing the parks.