Environmental Effects of Cities

Direct and indirect impacts, near and far, of urbanization on subsystems of Earth systems.

A city’s “urban environment” is the area the city occupies, directly impacted by the city’s use of materials, air, water, and land. A city’s “ecological footprint” is the space needed to support the city, equivalent to the physical and biological regions disturbed to provide resources to the city and accept its wastes. A city’s “metabolism” is the sum total of materials, fuels, water, and goods that flow into a city to sustain its populace and economy. Cities vary in size, from agglomerated urban settings of 5000 people or more to megacities, agglomerated urban settings with greater than 10 million population. Global cities are a subset of megacities, cities that set global economic and cultural trends. All cities impact the environmental impact. Large cities tend to have disproportionately greater environmental impact than less populace ones.

At the turn of the 21^st Century, cities occupied only 3% of Earth’s land surface; however their impacts extended across the globe. Cities’ voracious appetites for resources and their dispersal of pollutants into air, water and on land result in local, regional, national and global environmental degradation. For example, the city of Los Angeles, California in 2000 had a population of about 4 million people and city limits covered an area of 1290 sq km. The Los Angeles metropolitan area had over 12 million people and covered Los Angeles and Orange Counties. The greater Los Angeles area, a megacity, covered much of five counties and included over 17 million people. Direct effects of Los Angeles within the five counties of the megacity are city smog, displacement of native habitats, contamination of surface and unconfined ground waters, and deposition of litter on city streets and beaches. The megacity’s direct environmental impacts to the western United States include air pollutants that diminish visibility at national parks of the Intermountain west, mountains of landfills for urban waste, and diminished flow and increased salinity of the Colorado River. However, the direct impacts to the region are only the beginning of the megacity’s environmental impacts. Coal fired plants in the West and Midwest provide electricity to Los Angeles with associated environmental effects of surface and underground mining, coal combustion, and waste disposal. Power plant emissions send sulfur dioxide across national boundaries impacting Canada’s forests. The impact of cars driven in Los Angeles is not limited to their emissions. Materials for cars come from mines, chemical plants, manufacturing centers, and cities that dispose of wastes on land, in the air and into water. Beyond the impacts to local, regional, and global physical and biological environments are the impacts to local, regional, and global populaces to sustain the city’s appetite for goods and services. Los Angeles is one of 24,000 urban areas globally. It can be argued that the uneven distribution and unequal per capita consumption of Earth’s resources exemplified by Los Angeles exacerbate rifts among rich and poor nations and lead to war, famine, and pestilence.

Geographers study webs of relationships among people, places, and environment. Almost every field of geography address an aspect of urban environmental geography including: physical geographers who explain (a) some of the reasons cities are located where they are, such as, regional resources and connectivity to transportation corridors, and (b) probable consequences of urban development to Earth systems; and human geographers who explain (a) the growth of cities, such as, by migration and natural increase, and (b) probable consequences of urban development to social and behavioral systems.

History of Environmental Effects of Cities

In less than a few hundred years, the environmental effects of cities have grown from largely-absorbed-by-their-locale to globally pervasive and pernicious. Three hundred years ago, the world’s population of approximately 600 million lived in what today would be considered rural setting with scatterings of villages and towns and about two dozen cities with over 100,000 inhabitants. Even at their worst, the environmental effects of most cities were largely confined within city limits, local environmental sinkholes of misery, disease, stench, smoke-filled interiors, and outdoor scenes of rotting refuse and human feces; ecosystems supporting rats, vermin and disease; and social structures vulnerable to recurrent famine.

Cities changed irrevocably in response to widespread consumption of fossil fuels introduced during the Industrial Revolution and increased crop yields of the Green Revolution. Commerce and trade provided jobs. People migrated to cities. With more people, cities consumed more resources, and attracted more people. In 1800, only 3 percent of the world’s 800-900 million people lived in towns of more than 5000. Fewer than 45 cities had populations over 100,000. In 2008, over half of the world’s 6.5 billion people are urban. Cities have evolved from local and regional centers of trade into today’s drivers of national and global economies.

The history of environmental effects of cities is inseparable from the history of environmental effects of the 20^th Century. During the 20^th Century, cities' appetites for goods and services grew at a faster rate than their increase in population due to (a) increased per capita consumption, (b) socio-economic factors, such as cultural migrations, and (c) political and economic policies such as treating the costs to the environment as economic externalities. The metabolism of cities varies among developed versus developing nations and even within nations. An estimate of the daily intake and output of energy, air, and water for a city of million people in the United States in the 1980s estimated intakes of over 500 million kilograms of water, almost 10 million kilograms of energy, and almost 2 million kilograms of food. The daily output included somewhat less than 500 million gallons of sewage, almost a million kilograms of air pollutants, and 10 million kilograms of solid waste. Calculating and analyzing cities’ metabolisms and their ecological footprint challenge geographers to agree on methodology as well as to model flows of materials into and from cities.

Environmental Effects on Earth Systems

Every city on every continent impacts Earth. The cumulative environmental effects of cities are innumerable with feedback loops that make a full assessment of the total environmental impact of a city almost impossible. Assessing even the local effects of cities on their urban environment includes assumptions of costs and benefits, intangible values of quality of life, and issues of social justice. Although the litany of effects is long, it is possible to get a sense of the diversity of impacts and their scale by listing example of impacts for each of the subsystems of Earth systems: the geosphere, hydrosphere, atmosphere, biosphere, and anthrosphere.

Future Options

Environmental effects of cities are pervasive, persistent, and population driven. They are not inexorable. In fact, it can be argued that environmental impacts of populace concentrated in cities should be less than populace spread more evenly across Earth’s surface. Cities’ environmental problems challenge modern society’s mores because recent advances in quality of human life have been tied to per capita consumption, gross national product, and fuel consumption, all of which negatively impact the environment. Cities can and have reversed environmental degradation of their air, water, and land. The ‘’environmental miracle” of Japan of 1965-1985 not only cleaned up the fouled air and water of Japan’s rust belt but strengthened Japan’s economy establishing its reputation as the premier manufacturer of pollution control equipment. Collaborations of government, industry, and individuals, including scientific elites, has reduced acid rain from coal fired plant in Europe, banned CFC (chlorofluorocarbons), and reversed eutrophication of the Great Lakes.

Geography Matters

Environmental issues are issues of human geography as well as physical geography. The study of geography provides ways to appreciate differences among cities and their impacts. Urban environmental geography examines how physical geography influences the viability and vulnerability of urban settings. Human geography helps explain why migrations into and among cities has had greater impact on the environment than equivalent growth by natural increase.

The 20^th Century at first was ignorant of, and then denied environmental effects of cities, relegating debates to concerned scientists and environmental activists. Disparities among rich nations and poor nations driven by consumption now affect world balance of power and undermine world stability. Issues of environmental and social justice include the dynamics of international aid, consequences of famines, and politics of population policies. In 2007, former US vice president Al Gore and the UN International Panel on Climate Change received the Nobel Peace Prize for work to identify, quantify and publicize effects and probable consequences of human impacts on the environment. That the prize was given for peace is a signal that the 21^st Century may recognize that environmental effects of cities extend beyond city boundaries and beyond their global ecological footprint to the social welfare of the human species.

Genevieve Atwood

Cross-references:

Environmental History; Globalization; Industrialization; Inequality and Geography; Population Increase, Environmental Consequences; Rural Urban Migration; Social and Economic Impacts of Climate Change; and Urban Environmental Change.

Further readings and references:

Goudie, A. (2005). The human impact on the natural environment: past, present, and future (6th ed.). Malden, MA; Oxford: Blackwell Publishing.

McNeil, J. R. (2000). Something new under the sun: an environmental history of the twentieth-century world. New York: W.W. Norton & Company.

Population Reference Bureau. (2007). World population highlights: key findings from PRB's 2007 World Population Datasheet. Population Bulletin, 62(3) Retrieved 11/30/08, from http://prb.org/pdf07/62.3Highlights.pdf.

The Earth Institute at Columbia University. (2005). The growing urbanization of the world. Earth Institute News Archive Retrieved 11/30/08, from http://www.earth.columbia.edu/news/2005/story03-07-05.html.

U N Population Fund. (2007). State of the world population 2007: unleashing the potential for urban growth. Retrieved 11/30/08, from http://www.unfpa.org/swp/2007/english/chapter_1/index.html.

World Resources Institute, U.N.E.P., United Nations Development Programme, and the World Bank. (1996). World resources 1996-97: The urban environment. Retrieved 11/30/08, from http://www.wri.org/publication/world-resources-1996-97-urban-environment.