By 2030, the city of Pittsburgh wants more residents to easily access to places to walk, bike and enjoy nature. The goal is for every resident to be a 10-minute walk from a green space, and parks are just one part of that, said Chief Resilience Officer Grant Ervin.

"We're also looking at kind of existing green and open spaces that we have, like parks and parklets, as well as greenways that are already kind of part of the city's footprint, as well as vacant land and open space that might be designated as ... green space."

The effort is part the city's OnePGH plan, which was unveiled in April and will be funded by private companies, non-profits and foundations. The collaboration is also expected to tackle problems like homelessness and hunger, and create a map for eventual universal pre-K.

According to the Trust for Public Land, 91 percent of Pittsburghers do live that close to a park or green space, compared to 54 percent of Americans as a whole. Still, that means more than 28,000 Pittsburgh residents don't live within a 10-minute walk of green space.

One-third of U.S. residents don't have access to a park within a half mile, according to the 10-Mile Walk campaign. Researchers have found that access to green space improves mood and mental health, especially for low-income residents.

The 10-minute walk goal has been picked up by dozens of cities across the country, including Ann Arbor, Mich., Portland, Ore., and Philadelphia and State College, Pa.