Urban Ecology - Ecological Systems - page 291

Examples of urban ecosystem services include the mediation of local climate by
trees, the tempering of human behavior by green views, the reduction of stormwater
flows, provision of recreation, conversion of some pollutants to neutral forms, and
the sequestration of carbon dioxide in biomass, soils, and organic litter [ 56 ].
Cultural benefits also accrue to the biotic components of urban ecosystems. These
include a sense of place provided by ecological structures such as particular patches
of vegetation or streams. Environmental justice can be enhanced by a broader
understanding of the spatial distribution of hazards such as fire and exposure to
winds, and to the potential for mitigation and other positive services provided by the
biotic components of urban ecosystems.
Sustainability and Adaptive Processes
An emerging frontier in urban systems is the nature and processes of sustainability.
Sustainability is defined in two main ways. One definition suggests that
sustainability is the capacity to meet present needs without compromising the
ability of future generations to meet their own needs. A second definition focuses
on the reconciliation of demands within economic, social, and environmental
spheres that permit the entire integrated system to persist and continue to adapt to
change. This second definition is important for giving equal weight to the three
facets of the global hybrid system as well as accommodating social justice as a key
aspect of the social dimension. Indeed, some scholars define sustainability in terms
of economy, environment, and equity, following the assumption that a social
system that does not provide for equity is less likely to persist.
Sustainability, as the ability to adjust to changing conditions originating within
and beyond the system of interest, is closely related to the concept of resilience.
Resilience is the capacity of systems to experience disturbance and shocks and still
remain within a given structural or functional domain. Such resilience requires
adaptive processes ( Fig. 15.2 ). Adaptive processes are both social [ 57 ] and
bioecological [ 58 , 59 ], in keeping with the understanding of most contemporary
ecosystems as human ecosystems ( Fig. 15.2 ). Adaptive processes bring the
components of human ecosystems into the dynamic realm of sustainability and
resilience.
Sustainability has become a goal of many urban jurisdictions. This development
is the latest stage in an ongoing evolution of cities in industrial countries. The
industrial city was the epitome of overcrowding, contaminated water, and industri-
ally generated pollution, for example. Reformers followed two paths to correct the
flaws of the industrial city. One was to abandon it altogether. This strategy
motivated the establishment of suburbs, or of garden cities in green sites well
outside the shadow of the dark Dickensian industrial city. The second strategy
was to alter the industrial city itself. Providing clean water, removing waste,
alleviating overcrowding, and reducing the local impact of pollution were
hallmarks of this second strategy, which can be labeled, following historian
Martin Melosi [ 60 ], the “sanitary city.” The sanitary city installed infrastructure