Visitors to a National Park in West Virginia / WPublic Broadcasting

At the Center for American Progress in Washington, D.C., U.S. Interior department Secretary Sally Jewell said national parks had their highest visitation rates ever in 2014, with more than 400 million visits, and those numbers are expected to only increase in the next year, after the launch of President Obama's Every Kid in a Park program, which will eliminate park fees for every 4th grade kid and their family for a year. "This sends a message that parks are not just for wealthy white people, but for everyone."

National parks contributed $26 billion directly to the economy last year, said Jewell. And a few years ago, the entire outdoor recreation economy — covering everything from tent purchases to ski rentals — was estimated to be valued at $646 billion, and responsible for 6.1 million jobs.

These numbers show how outdoor jobs aren't just related to extractive industries, like fracking. "Communities can chose between jobs in the extractive and recreation and conservation industries. It's just not about extraction."

To preserve and grow the outdoor recreation economy, she called for a more thoughtful balance between conservation and development. She said one way to achieve this is "acting at the landscape level." For example, depending on the site, a place may be "appropriate or inappropriate for development; there are certainly places that are too special to develop." Landscape level planning, Jewell argued, can help create "long term health for both habitats and communities."

Other speakers weighed in on the outdoor recreation economy:

Paul Smith, a venture capitalist, is behind a group called Conservation for Economic Growth, which argues that open spaces have a direct economic impact. "And they have an economic value beyond their tourism value." He pointed to how real estate with a view of the water or another open space is always worth more than one without the view; how a higher-level floor in an apartment building is always worth more than one on a lower floor. "There's a value to wonderful views." Smith said the Commerce Department is expected to launch a study exploring open space's value.

Margaret Walls, senior fellow, Resources for the Future, said with climate change, the scenic natural systems that also provide crucial ecosystem services are only going to be worth more. The gorgeous wetland that protects a community from storms, or that scenic river headwaters that improves water quality, will be worth more the more it's needed.

Cam Bresinger, NEMO Equipment, said "numbers are powerful" and should be used by progressive candidates to promote the outdoor recreation economy in legislatures. "Give them the data they can use to build the argument." It should be that if a representative is from a part of the country where there are lots of ski resorts, hiking areas, or trails, it will be "inconceivable if they don't mention this."

Lastly, someone from the audience proposed more rigorous studies on the health benefits of nature. Specifically, he called for a National Institute of Health (NIH)-funded study comparing the benefits of drugs, therapy, or exposure to nature for veterans for post-traumatic stress disorder (PTSD). "Vets with severe PTSD could be given the opportunity to join the Conservation Corps, where we could study how well they respond to the medicinal effects of being out in nature." One day, national parks could be considered part of our healthcare system, too.