Urban Ecology - Ecological Systems - page 283

One important aspect of urban function is how equitably the ecological benefits
and risks in urban systems are distributed across the human population. This
concern, labeled environmental justice, first emerged in communities of color or
economically disadvantaged communities that were adjacent to contaminated sites,
or sites that produce hazardous pollution. The frequent locations of such
communities in topographic positions subject to flooding or landslides are other
cases of environmental injustice. An example is the disproportionate damage
suffered by low-lying neighborhoods such as the lower 9th Ward of New Orleans
during 2005 in the wake of Hurricane Katrina, or the location of informal
settlements with their flimsy construction in some South American cities on
erodible slopes. Poor and disempowered populations may be actively excluded
from desirable sites, as was the case with segregation practices historically in some
US cities, or they may be indirectly priced out of locating to sites on higher ground,
more distant from polluting businesses, or from facilities that process waste. The
patterns and mechanisms of environmental injustice suggest a principle:

Principle 11 : Bioecological processes are differentially distributed across the
metropolis and the limitation of services and excess of hazards is often associated
with the location of populations that are poor, discriminated against, or otherwise
disempowered.

Methodological Principles

Two methodological principles of urban ecology complete the survey of guiding
concepts for contemporary urban ecological science. These principles draw on
conceptual and empirical principles outlined above and can help shape future
urban research.
The first methodological principle deals with setting the boundary and scope of
the study system. This step is key to quantification and comparison within and
across urban systems. However, there is no a priori, universally correct scientific
specification of an urban system [ 40 ]. Using legally set municipal or town borders
may be convenient for policy purposes, but they may not be appropriate limits for
scientific research [ 28 ]. This is because a large urban system may be made up of
many such legally distinct jurisdictions. In addition, materials, energy, and infor-
mation that are important in structuring an urban system are likely to move across
political boundaries. For example, while it is possible and useful to measure species
richness in a city, the collection of species so identified may depend on and interact
with the larger, regional species pool [ 14 ]. A second example compares boundaries
chosen for watershed-based studies with those chosen for a policy analysis. The
17,150 ha Gwynns Falls Watershed, which extends from its headwaters in
Baltimore County to its confluence with Baltimore Harbor near downtown in the
City of Baltimore, provides a sampling transect. Measurements of stream water
quality and flow integrate across the two jurisdictions

[ 18 ]. In contrast,