There are 59 national parks in the U.S. and 8,565 state parks and a lot of local and city parks. The map looks full:

So at first glance, you might wonder why access to nature is part of the Green New Deal. And once again, the answer is equal parts poverty and inequality.
Although it would be nice for everybody to have a chance to see Yellowstone or Yosemite, what is at issue is access to nature for the poor and for those in distressed urban zones. Parks–and safe parks–are in short supply.
Some cities are blessed with either very large or very large numbers of parks within the city limits–Manhattan, San Francisco, Portland, for example. But where Minneapolis has 15% of its city surface reserved for parks, Indianapolis only has 5%. An organization called ParkScore puts Charlotte, North Carolina at the bottom of their list.
A city like Detroit, current population of 673,104, has 2.7 playgrounds per 10,000 residents and 0.5 public restrooms per 10,000. (Madison, Wisconsin has 11.6 parks per 10,000 residents while Hialeah, Florida has 1.2 per 10,000.) Detroit is right in the middle regarding parks per resident with 6 parks for every 10,000 residents, but how many of those parks are used, or even usable?
Urban parks tend to get taken over by drug dealers, gangs and the homeless. Reclaiming them for the rest of the population takes a concerted effort by the police, the community and the fabled Parks and Rec departments. All of whom are busy, so getting the resources to focus on the issue would require extra money for planning, reclamation, maintenance and security.
The Green New Deal could provide federal funding for this purpose, although it could be classed as normal infrastructure funding if any administration wanted to.
The National Park Service launched its Urban Agenda in 2015, with two-year pilot projects in 10 cities across the country. More than one-third of the parks they maintain are in metro areas. They are engaged in 1,500 urban park recovery projects.
The current administration has proposed funding the National Park Service at $2.7 billion in 2019. The National Park Service says it has an $11.6 billion backlog of deferred maintenance.
Recommendation for Green New Deal: Provide a one-shot funding allocation to cover the deferred maintenance. Secure federal funding for urban park reclamation, restoration and security for least-served urban areas at $5 billion a year.