green lung
noun1
An area of natural parkland within an urban region, supposed to replenish the air with oxygen.
- The Magaliesberg became something of a green lung to which people escaped, particularly over weekends.2006, Christof Mauch, Nathan Stoltzfus, Douglas R. Weiner, Shades of green: environmental activism around the globe, page 76:
- After the Games, the Park will remain protected, serving as a green lung for the surrounding boroughs and the Olympic Village residential area.2007, United Nations Environment Programme, Beijing 2008 Olympic games: an environmental review, page 74: