Built areas and systems
water, reduce stormwater runoff, cool the building and air, and provide a bit of
biodiversity (Hienet al.2007).
Metro-area border and inner urban-region ring
Awide greenbelt outside the metro area constrains outward urbaniza-
tion, while providing a trail system, cool clean air for the metro area, and con-
venient market-gardening areas (Munton1983,Pandellet al.2002,Whitehand
and Morton 2004, Bengston and Youn2006). A ring-of-parks, analogous to a green-
belt sliced by radial transportation corridors, loses the greenbelt connectivity,
but has more neighboring residents who can use and care for the parklands
(e.g., Budapest). Greenways or trails could connect the parks. Greenways partic-
ularly facilitate walking and biking recreation, but also provide water and habi-
tat protection (Briffettet al.2000,Briffitt2001,Fernandez-Juricic2000,Erickson
2006,Binford and Karty 2006). A green wedge projecting into a metro area pro-
vides proximity to greenspace for many residents, but especially facilitates recre-
ational movement between city and countryside. Green wedges also enhance
clean air flows in the city, and the movement of species from countryside to
urban greenspaces.
Narrowstream corridors in this metro-area border area are mostly straight-
ened, even discontinuous with water flows in underground pipes. A pipeline
corridor may be especially effective for wildlife movement, and maintenance
activities usually result in creating a strip of common edge species. Astring of
pearls,asatree-lined trail connecting small semi-natural patches (Forman 2004a),
facilitates walking recreation and some species movement between the small
patches or parks, which are easier to establish and protect than are greenways.
Patches around the metro-area border are extremely diverse. A golf course
is an intensive water, fertilizer, and pesticide user, and usually is biologically
impoverished because in construction the natural habitat heterogeneity was
largely homogenized, and now shrub cover, dead trees, and logs are scarce.
Anursery-plants area also pours on the water, fertilizer, and pesticide, while
serving as a major source of non-native and invasive species which are widely
dispersed across residential and commercial areas. A botanical garden, also using
water, fertilizer, and pesticide, grows an exceptionally rich collection of native
and non-native plants, and presumably is also a source of dispersing exotic and
invasive species. A market-gardening area, perhaps using still more water, fer-
tilizer, and pesticide, provides convenient fresh food and sometimes family and
social benefits, while often polluting the groundwater beneath. A wetland com-
monly absorbs stormwater which reduces flood hazard, supports rich biodiver-
sity, and provides swarms of seasonal mosquitoes. Finally a lake here usually is
ringed by development for the relatively wealthy, is polluted, and offers boating
and fishing recreation.