There are too many people coming to parks doing the wrong things. They treat the parks like popcorn playgrounds. They don't understand what the national parks mean.

One of the most unusual shuttles operates at the Lyndon B. Johnson National Historic Site in Texas, carrying visitors on a one and one-half hour trip past Johnson's birthplace, the family cemetery and ranch house, and through the ranch.

A boundary is really something artificial we made up. The ecosystem and landscape continue.

It's better to go to one place and stay put and see it than run around a lot of territory and see nothing.

You may or may not agree with Obama's policy prescriptions, but they are, by and large, serious attempts to deal with the biggest issues we face: a failing health care system, oil dependency, income stagnation, and climate change.

Doing all we can to combat climate change comes with numerous benefits, from reducing pollution and associated health care costs to strengthening and diversifying the economy by shifting to renewable energy, among other measures.

Many environmental battles are won by delaying a destructive project long enough to change the conversation - to allow new economic, political and social dynamics to emerge.

Governments have to conclude a fair, universal, and binding climate agreement, by which every country commits to reducing emissions of greenhouse gases.