Page 372 - Environment: The Science Behind the Stories

to 100 times saltier, even in summer Rural Suburban Urban environment as well. Some research
when salt is not applied. Such high salin- measures how natural amenities affect
ity kills organisms (FIGURE 2), degrades 600 1998 1999 property values. One study found that
habitat and water quality, and impairs 500 2000 2001 proximity to a park increases a home’s
streams’ ability to remove nitrate. 2002 property values—unless crime is per-
To study contamination of ground- 400 vasive. If the robbery rate surpasses
water and drinking water, researchers Mean annual chloride concentration (mg/L) 300 Chronic toxicity to 6.5 times the national average (as it
are using isotopes (p. 42) to trace freshwater life does in Baltimore) then proximity to
where salts in the most polluted 200 a park begins to depress property
streams are coming from. Baltimore is 100 Damage to values.
now improving water quality substan- land plants Other studies focus on environ-
tially with a $900-million upgrade of its 0 mental justice concerns (p. 158). These
sewer system. 0 10 20 30 40 50 have repeatedly found that sources of
Urbanization also affects species Percent impervious surface industrial pollution tend to be located
and ecological communities. Cities in watershed in neighborhoods that are less afflu-
and suburbs facilitate the spread of FIGURE 2 Salt concentrations in ent and that are home to people of
non-native species, because people Baltimore-area streams are high enough racial and ethnic minorities. Phoenix
introduce exotic ornamental plants and to damage plants in the suburbs and researchers mapped patterns of air
to kill aquatic animals in urban areas.
because urbanization’s impacts on pollution and toxic chemical releases
the soil, climate, and landscape favor Adapted from Kaushal, S.S., et al., 2005. and found that minorities and the poor
Increased salinization of fresh water in the
weedy generalist species over more northeastern United States. Proc. Natl. Acad. Sci. are exposed to a greater share of these
specialized native ones. In Baltimore, USA 102: 13517–13520, Fig 2. ©2005 National hazards. As a result, they suffer from
non-native plant species are most Academy of Sciences, U.S.A. By permission. higher rates of childhood asthma.
abundant in urban areas. In Phoenix’s In how many years did mean salt In Baltimore, researchers found a
dry climate, pollen from some non- concentrations in urban areas more complex pattern. Toxic release
native plants causes allergy problems surpass the level of chronic toxicity to sites were more likely to be in working-
for city residents. freshwater life? class white neighborhoods than in
Community ecologists study- African American neighborhoods. This,
ing the wild animals and plants that the researchers concluded, was a result
persist within Phoenix are finding ornamental vegetation shelter animals of historical inertia. In the past, living
that urbanization alters relationships from extreme conditions, and irrigation close to one’s workplace—the factories
among them. Compared with natural in yards and gardens provides water. that release toxic chemicals—was
landscapes, cities offer steady and In a desert city like Phoenix, watering something people preferred, and white
reliable food resources—think of boosts primary productivity and lowers workers claimed the privilege of living
people’s bird feeders, or food scraps daytime temperatures. Together, all near their workplaces.
from dumpsters. these changes lead to higher popula- Whether addressing the people,
Growing seasons are extended tion densities of animals but lower spe- natural communities, or changing
and seasonal variation is buffered in cies diversity as generalists thrive and ecosystems of the urban environment, CHAPTER 13 • THE URB AN ENVIR ONMENT : CREATING SUSTAIN ABLE CITIES
cities, as well. The urban heat island displace specialists. studies on urban ecology like those in
effect (p. 369) raises nighttime tem- Urban ecologists in Phoenix and Phoenix and Baltimore will be vitally
peratures and makes temperatures Baltimore are studying social and informative in our ever-more-urban
more similar year-round. Buildings and demographic aspects of the urban world.

Urban ecology helps cities toward Researchers in the field of urban ecology hold that cit-
sustainability ies can be viewed explicitly as ecosystems and that the fun-
damentals of ecosystem ecology and systems science (Chapter 5)
Cities that import all their resources and export all their wastes apply to the urban environment. Major urban ecology projects
have a linear, one-way metabolism. Linear models of production are ongoing in Baltimore and Phoenix, where researchers
and consumption tend to destabilize environmental systems and are studying these cities explicitly as ecological systems (see
are not sustainable. Proponents of sustainability for cities stress the THE SCIENCE BEHIND THE STORY, above).
need to develop circular systems, akin to systems found in nature, To help cities reduce their environmental impacts while
which recycle materials and use renewable sources of energy. improving quality of life for their citizens, urban sustainability 371

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