green skeleton
n. The parkland, gardens, playing fields, and recreation areas that course through a city or region.
For these and innumerable other reasons, utilizable parks and urban green areas will continue to be at a premium in towns that value each square foot of space in terms of development opportunity. These places are most effective when they function as a network, and ideally provide a green "skeleton" that affords continuous access to recreation and nature.
—Maxwell Vidaver, “Green Parks Are More Than Green Recreation,” Global Site Plans, April 18, 2013
The planners want to see Torontonians come together on a set of planning values . . . Agreement, for example, on the broad precepts of design, transportation, on the meaning of economic prosperity, on the so-called "green skeleton" (parks and recreation areas) and on housing choices.
—Michael Valpy, “City's chief planner a man with a vision,” The Globe and Mail, March 02, 1999
1991 (earliest)
One goal of ecologists is "biodiversity." To understand their vision, imagine flying over the Pacific Northwest in an airplane today. The human population below has doubled the past 40 years and could easily double again in the next 40. The landscape often looks as if it has been sprayed with buckshot. Clear-cuts, clumps of farms, and subdivisions have cut holes in the forest fabric like measles and mange.

In the future, a new pattern of forest clumps and connecting corridors could overlay this like a green web.

Political boundaries might become geographic ones. Instead of straight lines that cut across the landscape, jurisdictions might be based on watersheds, an area of land drained by a river system. A county line might ramble along ridges, for example, an idea contained in an environmental philosophy called "bioregionalism."

Scientists tossed out the idea of a "green skeleton" of natural habitats designed to promote as many species as possible.

The skeleton's backbone would be the parks, wildernesses and old-growth forest preserves along the region's mountain chains.

Its bones, or arteries, would be tree-filled "riparian zones" that would follow streams and rivers to saltwater.
—Bill Dietrich, “Blueprint for wildlife, trees in the works,” The Seattle Times, July 07, 1991