Greenspaces 111Atafiner scale, a community garden provides family food, social benefits,
and rich food for wildlife. A sewage-treatment facility cleans human waste, but
is often a source of pollution overflows in heavy storm events and air-borne
pathogenic microorganisms. A solid-waste/recycling site also addresses the prob-
lem of societal wastes, and is a magnet for concentrations of rats, gulls, or other
scavengers, often including people who recognize wastes as economic value.
Outer urban-region ring
In the outer portion of an urban region, a broad-scale pattern of corri-
dors, often connected into networks, is superimposed on the matrix and large
patches. A river corridor upriver of the metro area may be quite clean or be
heavily polluted by agricultural runoff, whereas downriver of the city, river
water ispollutedbyurbanandindustrial processes. Highway corridors have
traffic-noise-created degradation zones on each side, and serve as major barriers
to walkers and wildlife movement (Cuperuset al.2001). The emerald network of
large natural-vegetation patches connected by green corridors is an effective flex-
ible solution to sustain wildlife in the face of urbanization and climate-change
processes.
Forest/woodland, grassland, desert, and especially cropland are the back-
ground matrix and landscapes in urban-region (urb-region) rings. As such, they
are predominant sources of species and form the framework for water con-
ditions. Forest/woodland is particularly valuable for recreation in addition to
wood production and wildlife cover, though flooding, erosion, and sedimen-
tation are chronic problems (Theoboldet al.1997, Konijnendijket al.2005).
Grassland and desert are both subject to erosion, sedimentation, and loss of
wildlife. For low-density residential areas, medium or relatively small house-lot
sizes overwhelmingly degrade biodiversity and water conditions, whereas very
large house lots may maintain only moderately degraded ecological conditions.
The latter, therefore, may be suitable as buffers around large protected natural
areas.
Atthefine scale, a dendritic stream-corridor network is especially important
in the outer urban-region ring. The stream network within large natural areas
has a connected integrity which facilitates fish movements. On the other hand,
in an agricultural area the stream network usually has narrow strips of ripar-
ian vegetation that provide shade and fallen wood as fish habitat, but that do
relatively little to prevent stream pollution from runoff of eroded sediment and
excess fertilizer. Trees and other woody vegetation along stream/river channels
is largely removed by seasonal floods in some mountain areas (e.g., Santiago,
Chile), and by human action in parts of England where channels are managed
somewhat like large stormwater drains. Hedgerows often facilitate species move-
ment across the landscape and reduce agricultural runoff. Lakes and especially