UNITED STATES - 2015/08/07: A young woman is sitting on a rock near Yavapai Point on the South Rim overlooking the Grand Canyon with clearing clouds after a thunderstorm in the Grand Canyon National Park in northern Arizona, USA. (Photo by Wolfgang Kaehler/LightRocket via Getty Images)

The Grand Canyon, brought to you by Budweiser. Verizon signs throughout Yellowstone. The thought of advertising in our national parks is nauseating. But it could happen.

Earlier this month, the National Park Service released a proposed plan to begin aggressively seeking private sponsorship for park projects to make up for dwindling public funding. Park leaders would be encouraged to spend official time soliciting donations from individuals and corporations. Anything from sponsoring a bench to designing, building, and even operating a park building would be allowed.

The plan stirs up a fundamental debate about our public goods -- what they are, who owns them, and how they should be managed.

On one side, private interests are vying to influence and control America's untapped public space and resources. Like Coca Cola, which in 2011 tried to halt a planned ban on the sale of plastic water bottles in Grand Canyon National Park. The company owns Dasani, the most popular U.S. brand of bottled water, and considered the ban a hit to their bottom line. The National Park Service's new proposed plan would allow even more private influence on policies and decisions to protect our public resources.

On the other side, communities across the country are standing up to corporations that want to control and profit off of the things we own in common. Just last week, after an eight-year fight, a coalition of advocates in Oregon blocked the multi-national corporation Nestlé from bottling water from the Columbia River Gorge. Their unprecedented county ballot measure that bans all commercial water bottling passed by 69 percent and paves the way for other communities looking to protect public resources.

Our public parks and resources allow everyone -- from working families to the wealthiest -- to enjoy and experience nature and live healthy lives.

Things we hold in common -- parks, public buildings, public resources -- are a big part of what makes a society. They need protection and more public investment, not private influence.