Populations worldwide are increasingly concentrating in cities. A rural
exodus, combined with overall population growth, has led to this unprecedented
and rapid growth of urban populations, reaching a rate of 4% per year in
certain Asian and African cities (Jegasothy, 1999). Will such population
migration and concentration lead to increased environmental damage? Population
growth on its own heightens the global environmental impact of humans. The
question of concern is whether changing population distribution patterns,
resulting from economic and social forces, will increase or decrease per
capita degradation. A selection of studies suggest that the influence of
urbanization patterns on the surrounding environment can be negative or
positive depending on the development, economic and political circumstances
within which urbanization takes place. Additionally, the pace of urbanization
affects its environmental outcomes.
Why Urbanization Matters
Cities have the potential to cause greater environmental degradation than
less dense population structures, because the concentration of people overwhelms
local resource capacity, creating demand for the importation of a vast array
of goods. The consumptive resource demands of cities are especially acute
in the case of energy. The transport of food and water into the city, as
well as of waste away from the city, creates transportation energy demands
in excess of those found in rural communities, where resources are supplied
and disposed of more locally (Brown & Jacobson, 1995). In addition to
requiring the transport of water, cities can be especially water-intensive
due to waste and misuse of imported or scarce local water resources (Brown
& Jacobson, 1995). Furthermore, urbanization accelerates the exploitation
of local water resources due to population concentration (Jegasothy, 1999),
often at rates beyond natural replenishment. Many urban residents pay little
for water, while agricultural users may be more acutely aware of its true
cost and scarcity, leading to more efficient use. Similarly, rural water
users who must pump their own well or retrieve their daily water from a
local communal supply will have a vested interest in water conservation
not shared by urban users who must simply turn on the faucet. Additionally,
the concentration of people in urban environments often leads to overshoot
of the assimilative capacity of local air, water and land (Brown & Jacobson,
1995). Up to a certain population density and level of emissions, the surrounding
environment can absorb and assimilate human wastes without degrading the
environment. However, cities rapidly exceed this critical threshold. In
contrast, cities may also have the potential to decrease per capita environmental
impact as people reduce vehicle miles traveled and the amount of land consumed
per household (Kahn, 2000). This is largely a MDC phenomenon, however, as
it requires infrastructure and urban planning capacity.
Overview: Factors Influencing the Impact of Urbanization on the Environment
The effect of urbanization on the environment varies greatly with the developmental,
economic and political characteristics of the growing city and its inhabitants.
As in rural areas, poverty is a primary driver of environmental degradation
in cities (Hope & Lekorwe, 1999) as personal wealth affects one's locational,
resource consumption and waste disposal patterns. The promotion of economic
development and industries of certain types will also affect the form and
extent of environmental challenges faced as a result of urban growth (Marcotullio,
2003). Finally, government policies that influence urban and economic growth,
and those that directly impact resource consumption and waste disposal practices
(i.e. subsidies and infrastructure) will shape the consequences of population
agglomeration (Hope & Lekorwe, 1999; Marcotullio, 2003; Jegasothy, 1999;
Kahn 2000).
Urban Poverty
The migration of the rural poor to urban areas of the developing world,
where they hope to find greater economic opportunities resulting from an
urban development bias, has created a growing population of urban poor (Hope
& Lekorwe, 1999). Urban poverty tends to enhance the environmental stress
of urbanization due to the urban poor being forced to live on ecologically
fragile lands and unsustainably harvest surrounding resources (such as fuelwood
and marginal agricultural land) (Hope & Lekorwe, 1999). Additionally,
poor urban communities lack the infrastructure necessary to accommodate
such dense populations, leading to environmental and human health degradation
from poor solid waste management and water sanitation. Such locally acute
environmental problems affecting poor cities are called "brown"
environmental problems (Hope & Lekorwe, 1999: 841; Marcotullio, 2003:
229). As urban slums develop on the outskirts of coastal cities, severe
coastal and marine pollution may result from urban development and lack
of infrastructure to accommodate poor inhabitants (Hope & Lekorwe, 1999).
The way to address urban poverty-induced environmental degradation is to
help people to "work their way out of poverty" (Hope & Lekorwe,
1999: 854).
In contrast to the effects of poverty, which lead both urban and rural peoples
to mine their local resources to attain minimal consumption levels, wealth
can lead to over consumption, but also the capacity to manage and mitigate
human impact. The distinct set of environmental problems that result from
wealthy urban societies have been coined "green" problems (Marcotullio,
2003: 229). These problems tend to involve less acute environmental degradation
and more regionally and temporally dispersed consequences having greater
ecosystem destruction potential, as opposed to detrimental human health
effects (Marcotullio, 2003: 229). Wealthier cities can provide the infrastructure
necessary to accommodate the consumption demand and waste generated by their
urban population. Additionally, technologies developed and adopted by wealthy
nations can mitigate the impact of increased resource consumption. One illustrative
example is the increase in urban air quality in California as a result of
vehicle emissions reductions, despite an increase in urban populations and
vehicle miles traveled (Kahn, 2000). Wealth may also decrease the pressures
of urbanization on the environment by reducing urban population growth.
The US has seen increasing wealth lead to suburbanization after initial
urbanization. However, the suburbanization trend has had its own set of
increased environmental impacts (including greater fuel oil and land consumption
as well as vehicle travel) (Kahn, 2000).
Urban Development
Cities promote and are promoted by economic development and growth, as concentration
of human and physical capital increases the efficiency of the production
of goods through economies of scale and agglomeration economies (Jegasothy,
1999). The type and pace of development, which is dictated by local resources,
government priorities and the global market, will shape the environmental
consequences resulting from the selected urban development path. One study
finds that the urban and industrial development of Asia, associated with
globalization, has created a layering of environmental challenges (Marcotullio,
2003). The speed of recent urbanization and industrialization in many Asian
economies, that study suggests, has produced the concurrent onset of previously
temporally spaced causes of environmental degradation. In contrast to the
slower industrialization of Western nations, the recent globalization boom
has hastened the urban transition in some economies, such that industrializing
cities are still learning to solve "brown" environmental problems
as rapid development throws "gray" and "green" environmental
problems into the degradation mix simultaneously (Marcotullio, 2003: 229).
Additionally, the market-determination forces of globalization have dictated
the type and intensity of industrialization and associated infrastructure
development associated with urbanization (Marcotullio, 2003). Cities that
emerge in the global economy as manufacturing hubs will have more intensive
and environmentally disruptive infrastructure and byproducts, such as massive
transportation networks and chemical waste (Marcotullio, 2003), than will
cities developed around human-intensive industries or areas that remain
rural and agricultural.
Government Policy
Government policies that promote or react to urbanization substantially
shape the impact of population concentration on the local and global environment.
Governments may inadvertently increase urbanization's environmental degradation
through subsidizing the growth of cities and promoting inefficient use of
natural resources (Brown & Jacobson, 1995). In contrast, governments
can take (and many have) important policy steps towards urban sustainability.
In urban areas facing "brown" environmental challenges, adequate
provision of infrastructure can mitigate both environmental and human health
consequences of urban concentration (Marcotullio, 2003). In developing and
developed nations alike, governments may seek to promote low-cost mass transit
as opposed to individual vehicular travel or inordinately expensive light
rail systems, and may preserve open space and fragile environments through
land use planning (Brown & Jacobson, 1995). Effective land management
and appropriate housing provision "are crucial for mitigating the impacts
of urbanization on environmentally fragile land and other resources,"
especially in cities where poverty drives unsustainable land and resource
exploitation (Hope & Lekorwe, 1999: 851). As previously noted, government
policies aimed at lessening poverty are the best way to sustainably reduce
the degradation resulting from poverty-driven urbanization (Hope & Lekorwe,
1999). Government capacity to effectively respond to urbanization and environmental
degradation is shaped not only by funding, but also by the degree of government
decentralization. Decentralized governments may be better suited to quickly
address the local "brown" challenges of urbanization facing much
of the developing world and to mitigate further effects of rapid population
growth (Marcotullio, 2003).
Conclusions
In sum, the pace and economic context of urbanization will dictate the extent
and character of its environmental impact. Rapidly urbanizing communities
composed largely of poor people will tend to have greater environmental
consequences than will slowly urbanizing rich communities with the time
and capacity to plan for and mitigate the environmental impact of additional
people. Environmental degradation results from most any human activity,
such that urbanization concentrates these effects, overwhelming the capacity
of the environment to assimilate pollution. Urban residents use more energy
than do rural residents as a result of the transportation costs to obtain
food, fuel and water inside a city. In contrast, cities can constitute a
more efficient use of space, such that urban planning in wealthy nations
promotes population density in order to control sprawl, which has harmful
environmental repercussions of its own. Thus, urbanization's nuances dictate
the precise impact of current trends towards increasing population concentration.
It is not impossible to have a sustainable city. However, it will take foresight
in planning, significant government capacity, and a level of wealth and
commitment among its inhabitants to make the system work. Finally, in assessing
the impacts of urbanization we tend to overlook the utility of fostering
sustainable rural economies and promoting fertility reduction in order to
decrease the economic and population pressures that drive urbanization in
the first place, thereby reducing environmental degradation at one of its
sources.
Brown Lester R. and Jodi L. Jacobsen, "The Future of Urbanization:
Facing Ecological and
Economic Constraints", in Population and Environment , D. Heddy
(editor), 1995, Ch. 10, pp.132-149.
Hope, Kempe Ronald, Sr.; Lekorwe, Mogopodi H. (1999), "Urbanization
and the Environment
in Southern Africa: Towards a Managed Framework for the Sustainability of
Cities", Journal of Environmental Planning and Management v42,
n6 (November 1999): 837-859.
Jegasothy, K. (1999), "Population and Rural-Urban Environmental Interactions
in Developing
Countries", International Journal of Social Economics v26, n7-8-9
(1999): 1027-1041.
Kahn, Matthew E. (2000), "The Environmental Impact of Suburbanization",
Journal of Policy
Analysis and Management v19, n4 (Fall 2000): 569-586.
Marcotullio, Peter John (2003), "Globalisation, Urban Form and Environmental
Conditions in
Asia-Pacific Cities", Urban Studies v40, n2 (February 2003):
219-247.
PS - see http://www.msnbc.msn.com/id/17966852/site/newsweek/ for a recent Newsweek global rating map that looks at how successfully countries have addressed "green" and "brown" issues - the developed nations are clearly the green leaders and the developing nations are clearly struggling to address their increasing load of new "brown" issues.