National Parks probably have never been entirely immune from political influences, whether they came out of Washington, D.C., or close to a park's boundaries. But there's an argument that can be made, one backed up by evidence, that the past 50 years have seen the most attempts to subvert the mission of the National Park Service to preserve and protect natural resources unimpaired for the enjoyment of future generations.

Jon Jarvis, the 18th director of the National Park Service under President Obama, and his brother Destry, who has a long career tied to conservation and the national parks, to discuss their new book, National Parks Forever, 50 Years Of Fighting And A Case For Independence. In it they call for the National Park Service to be broken out of the Interior Department in a bid to reduce political interference on the agency.