The nation's front yard -- the National Mall in Washington, D.C. -- is hammered pretty hard each year by more than 25 million visitors. To reduce their impact on the grassy expanse, Interior Secretary Ken Salazar has directed the National Park Service to better manage the promenade that stretches from the Lincoln Memorial to the U.S. Capitol.

Canada's government is lagging behind much of the world when it comes to protecting marine areas along the country's borders, according to the Canadian Parks and Wilderness Society.

As Yosemite National Park officials work to draw up a defensible plan for managing visitors in the Yosemite Valley, they are striving to delicately balance preservation of resources against recreation.