There are external and internal influences that can impact units of the National Park System. Urban sprawl can strangle parks and their natural resources. Wildfires can sweep across boundaries and into parks. Rivers can flood and wash out trails and roads, as we saw last June at Yellowstone National Park.

Today we're going to be talking about looming threats to Yellowstone and Cape Hatteras National Seashore.

In the case of Yellowstone, it's a gold mine proposed to be sunk into a mountain towering over the park's northern entrance at Mammoth Hot Springs.

At Cape Hatteras, it's the Atlantic Ocean and the natural dynamics of barrier islands, which were not designed by nature to remain in one place. Instead, they shift as the ocean erodes beaches and moves sand about.

In both of these cases, there are solutions in sight. The question is whether they'll succeed.