Urban Ecology - Ecological Systems - page 280

designers and developers will be required. These examples suggest a principle to test
in further application:

Principle 7 : Urban designs and development projects at various scales can be
treated as experiments to expose the ecological effects of different design and
management strategies.

Principles Concerning Urban Function

The tradition in both the social and biophysical sciences to see urban areas as
distinct and opposed to nature has resulted in a bias against finding natural pro-
cesses in City-Suburban-Exurban systems. Both the pioneering research in land-
scape architecture and urban ecology [ 5 ] as well as the more recently established
projects [ 13 ] have, however, confirmed and extended the understanding of ecologi-
cal processes as parts of cities and their more extensive urban mosaics. Several
examples show the power of bioecological phenomena in urban contexts.
In Philadelphia and Boston, buried floodplains, thought to have been engineered
in a reliable stormwater management structure or filled to provide substrate for
building, continued to manifest higher levels of soil water and were associated with
property damage and abandonment [ 32 ]. In Philadelphia, the collapse of the sewer
that had replaced Mill Creek was a catastrophic outcome of ignoring the function of
the urban landscape. Landscape designs envisioned with the participation of neigh-
borhood residents account for hazard and vulnerability, and provide an opportunity
to convert a disturbance prone site to an open space amenity. Such sites can
contribute constructively to regional stormwater management, recreation, and
education.
A second example shows the capacity of open space to perform biogeochemical
ecosystem functions in the urban matrix. Nitrate pollution in streams can be used as
an index of environmental quality to assess ecosystem function. Researchers who
started the Baltimore Ecosystem Study expected suburban lands to be detrimental
to the environmental quality of the urban mosaic. This hypothesis was suggested by
the large amounts of nitrogen fertilizer and water applied to many American lawns.
When small watersheds that drain areas having different amounts of green space in
their landscapes were studied however, it was discovered that the suburban

subwatersheds exhibited relatively high nitrate retention [ 18 , 33 ].
A third example of the role of ecological processes is shown in the net carbon
flux between surface and atmosphere. In a location near the boundary between
Baltimore City and County, an atmospheric flux tower assesses the upward versus
downward movement of moisture, temperature, and carbon dioxide, among other
factors. Although the urban area is a net generator of carbon dioxide to the
atmosphere due to the use of fossil fuels for heating and transportation, there is
lower net flux on weekends and when the wind blows across areas of higher
vegetation cover compared to winds from areas or greater built cover.