Across the National Park System, there is an estimated half-a-billion-dollars of obligations owed concessionaires who run lodges, restaurants, and even some activities, for the National Park Service.

It’s a sum that, while Park Service officials say is manageable, has seemingly stifled concessions competition in some parks and led the agency to divert tens of millions of dollars from some parks to others to reduce the debts.

At Grand Teton National Park in Wyoming, the outstanding amount is more than $57 million. At Glacier National Park in Montana, it’s $22 million. At Grand Canyon National Park in Arizona, it’s nearly $100 million. At Yellowstone National Park, the sum is $21.5 million.

Read more at National Parks Traveler