Urban Ecology - Ecological Systems - page 274

A new wave of urban ecology is currently on the rise. It is characterized by
several features that differentiate it from prior instances of urban ecology, and make
it more comprehensive than earlier approaches. First, it attempts to unify social and
biological knowledge, concerns, and approaches [ 12 ]. Second, it acknowledges and
exploits spatial heterogeneity and fine-scale dynamics as a feature and cause of
urban change. Third, it seeks to understand the controls of biogeochemical pro-
cesses throughout urban systems, including retention, fluxes, and leakage of limit-
ing nutrients and pollutants. Contemporary urban ecology brings the three
previously separate goals together for the first time.
Will this current interest in urban ecology wane, as did the previous ones in the
USA? One difference between the current manifestation of urban ecology and the
previous ones is institutional support. The pioneers of urban ecology in Europe,
Japan, and the USA did not have long-lasting research support. As a result, their
pioneering efforts were sometimes short-lived. Now there are two urban Long-
Term Ecological Research (LTER) sites in the USA, and International Long-Term
Ecological Research programs and Zones Ateliers are including urban areas
among their rosters. Already the US LTER urban sites are 13 years old. Such
longevity promotes interdisciplinary collaboration, continued use of research
areas, developing ongoing relationships with communities and decision-makers,
and accumulation of lengthy data runs which can expose causal links and the role
of pulse events [ 13 ]. Acknowledging that urban areas both contribute to and are
vulnerable to global changes [ 13 ] will tend to keep them in focus in ecological
science.
Examples
Urban ecology is such a diverse science that examples are required to give a sense
of its breadth.
Patterns of diversity and abundance associated with urbanization are complex
and competing explanations exist. Tests of island biogeography theory in urban
areas find that species-area relationships are preserved in urban patches [ 14 ].
However, in some studies, patch size influenced species composition rather than
species richness as a result of organisms at higher trophic levels being preferentially
lost from smaller patches [ 15 ]. Attempts to directly quantify the extinction and
colonization processes that island biogeography relies on have shown that immi-
gration and extinction characterize different kinds of patches [ 16 , 17 ]. The species
composition in a patch is the result of species colonizing the novel habitats formed
by urbanization along with those remaining after local extinctions due to isolation
or habitat alteration. One prediction of the view of complex causes of urban
biodiversity is that urban habitats are not always less diverse than rural patches.
Rather, diversity depends on the sum of extinction and colonization rates, which
differ regionally and taxonomically. At moderate levels of urbanization, species
richness may actually be higher than in nearby wild lands.