18 0Built systems, built areas, and whole regions
which may provide accessible recreation opportunities and are major multi-
directional sources of species moving into the city.
The problem to be overcome is that the city almost certainly will grow, e.g.,
from small to medium. About a century ago Frederick Law Olmsted designed
Boston’s much-heralded emerald necklace near the edge of the city, and Antoni
Gaudi designed Parque Guell (Color Figure40)onthe outskirts of Barcelona.
Analogously, the establishment of greenspaces, including large ones, on the
edge of small cities is apriority.Such parks will well serve the larger city of the
future.Metropolitan-area form
[A4]Half of the metro areas adjoin major physiographic features, often on two
sides, that constrain outward urbanization spread(Figure7. 9).
Adjacent seacoasts (San Diego, Barcelona) and lakeshores (Chicago) tend to
produce elongated metropolitan areas, and consequently long stretches of pol-
luted seawater, of damaged or destroyed coastal ecosystems, and of degraded
recreational resources. Adjacent mountain ranges (Sapporo, San Diego/Tijuana)
tend to have considerable development on nearby slopes, with associated flood
hazards, erosion/sedimentation problems, reduced visual quality, and so forth.
The regional geometry also makes major transportation networks particularly
difficult. Protecting nearby slopes with natural vegetation and establishing
coastal natural areas and parks long enough to maintain clean water areprior-
ities.Focusing development around satellite cities or other locations away from
slopes and coastlines is also a key part of the solution.
[A5]About half of the metropolitan areas are compact with 0--2 major built lobes, while
metropolitan areas with several (4--9) lobes have a highly convoluted form(Figure7. 10).
Acompact metropolitan areahas a minimal perimeter and hence degrades
outside greenspaces the least. Without strip-development corridors it also poses
theleast disruption of regional connectivity for wildlife and major stream/river
corridors. With people of a compact metro area being closer, on average, to
thecity center, public transport can be efficient. In contrast, several built
lobes projecting outward from a metro area suggest prominent strip develop-
ment along major radial transportation routes, with associated shortcomings
as described above. The long metro-area border means that much surrounding
greenspace is degraded. Maintaining a relatively compact form provides impor-
tant benefits.
[A6]Metropolitan areas, on average, have 3.5 major built lobes and 2.3 major greenspace
wedgeson their perimeter, with lobe and wedge number positively correlated(Figure7. 10).