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Urban environment

Urban areas do not have only local environmental impacts but also large so-called 'ecological footprints' (WWF 2000). In their immediate vicinity, cities have a variety of impacts: conversion of agricultural or forest land for urban uses and infrastructure, reclaiming of wetlands, quarrying and excavation of sand, gravel and building materials in large quantities and, in some regions, deforestation to meet fuel demand. The use of biomass fuel also causes indoor and outdoor air pollution. Other effects can be felt further afield such as pollution of waterways, lakes and coastal waters by untreated effluent. Air pollution from cities has an impact on residents' health as well as on vegetation and soils at a considerable distance. Urban transport contributes to air pollution and the large concentration of cars and industries in cities causes the lion's share of urban global greenhouse gas emissions.

Cities are often located in prime agricultural areas. If this land is converted for urban uses, this puts additional pressure on nearby areas that may be less suitable for agriculture. Urbanization in coastal areas often leads to the destruction of sensitive ecosystems and can also alter the hydrology of coasts and their natural features such as mangrove swamps, reefs and beaches that serve as barriers to erosion and form important habitats for species.

Low to medium density residential areas (urban sprawl) around urban centres are common in the developed world. Well developed infrastructure and the increasing use of the car have facilitated this trend. Urban sprawl has an especially damaging effect on the environment associated with the increase in use of private motorized transport. Furthermore, low density development occupies proportionally larger areas of land per capita.

Facts about cities
  • In cities of the developing world, one out of every four households lives in poverty; 40 per cent of African urban households and 25 per cent of Latin American urban households are living below locally defined poverty lines
  • Fewer than 35 per cent of cities in the developing world have their wastewater treated
  • Between one-third and one-half of the solid wastes generated within most cities in low and middle income countries are not collected
  • 49 per cent of the world's cities have established urban environmental plans
  • 60 per cent of the world's cities involve civil society in a formal participatory process prior to the implementation of major public projects
  • Buses and minibuses are the most common (used by most people) mode of transport in cities; cars are the second most common and walking the third
  • 5.8 per cent of children in cities of the developing world die before reaching the age of five years
  • some 75 per cent of the world's countries have constitutions or national laws that promote the full and progressive realization of the right to adequate housing
  • One out of every four countries in the developing world has constitutions or national laws which prevent women from owning land and/or taking mortgages in their own names
  • 29 per cent of cities in the developing world have areas considered as inaccessible or dangerous to the police
Sources: GUO 2001 and Panos 2001

The ecological footprints of cities

An ecological footprint is the area of productive land and aquatic ecosystems required to produce the resources used, and to assimilate the wastes produced, by a defined population at a specified material standard of living, wherever that land may be located.

London Trust Co-founder Herbert Girardet has calculated that the ecological footprint of London - with 12 per cent of the UK population and covering just 170 000 ha - comes to some 21 million ha or 125 times the surface area of the city itself, equivalent to all the productive land in the United Kingdom.

William Rees - Professor of Community and Regional Planning at the University of British Columbia - has made an ecological footprint analysis of his home city of Vancouver, Canada. This indicates that Vancouver appropriates the productive output of a land area nearly 174 times larger than its political area to support its lifestyle. Other researchers have found that the aggregate consumption of wood, paper, fibre and food by the inhabitants of 29 cities in the Baltic Sea drainage basin appropriates an area 200 times larger than the cities themselves.

Scientists have calculated that a typical North American city with a population of 650 000 people would require 30 000 km2 of land, an area roughly the size of Vancouver Island in Canada, to meet its domestic needs without including the environmental demands of industry. A similarly sized city in India would require only 2 900 km2.

Sources: Global Vision 2001 and Rees 1996

Water is a key issue in urban areas. The intensity of demand in cities can quickly exceed local supply. The price of water is typically lower than the actual cost of obtaining, treating and distributing it, partly because of government subsidies. As a result, households and industries have little incentive to conserve water (UNEP 2000). Pollution from urban run-off, sewage and untreated discharges of industries has adversely affected many water bodies, leaving many cities with unsafe water supply.

Although local environmental problems tend to diminish with increasing income levels, other environmental problems tend to become worse (McGranahan and others 2001). The most obvious are high levels of energy use and increasing levels of consumption and waste production. Urban residents rely heavily on fossil fuels and electricity, and wealthy cities tend to use more energy and produce more waste.

Inadequate waste collection and waste management systems are the cause of serious urban pollution and health hazards, especially in cities in developing countries. Cities in industrialized countries are now also facing the consequences of past environmentally damaging production techniques and inadequate waste disposal. This has resulted in many different forms of pollution and in particular the formation of brownfields: abandoned, vacant or underused former industrial areas where redevelopment is hampered by environmental problems and lack of adequate information on contaminated land management (Butler 1996). Another problem emerging in developed countries is the lack of suitable landfill sites to cater for the increasing demand for solid waste disposal.

Population of selected major cities of the world by region (millions)

Ten of the world's megacities are in Asia and the Pacific - Tokyo, with more than 26 million inhabitants, is currently the world's largest city

Source: United Nations Population Division 2001a

Worsening environmental conditions can have serious effects on human health and welfare, particularly for the poor (Hardoy, Mitlin and Satterthwaite 1992). Poor sanitation creates environmental and health hazards particularly by direct exposure to faeces and drinking water contamination. Air and water pollution cause chronic and infectious respiratory disease, water-borne diseases such as diarrhoea and intestinal worm infections, increased mortality rates particularly among children and premature deaths - especially among the poor (OECD-DAC 2000, Listorti 1999, Satterthwaite 1997, McGranahan 1993, Hardoy, Cairncross and Satterthwaite 1990). However, worldwide epidemiological and demographic information suggests that survival rates are better in cities than in rural areas because of better access to health services (UNCHS 2001b). The urban poor are particularly exposed because of their location and because they have limited resources with which to compensate for these problems by buying potable water, securing medical care or escaping floods.

There are many other less quantifiable but nonetheless important environmental impacts, such as loss of green space in urban areas, destruction of special local ecosystems, noise pollution, and aesthetically unpleasant sights and smells. These not only constitute a genuine loss of well-being but they can also erode civic pride and lower morale, leading to indifference and cynicism locally and to a negative image externally.

The relatively disproportionate urban environmental footprint is acceptable to a certain extent because, for some issues, the per capita environmental impact of cities is smaller than would be made by a similar number of people in a rural setting. Cities concentrate populations in a way that reduces land pressure and provides economies of scale and proximity of infrastructure and services (Hardoy, Mitlin and Satterthwaite 2001). Urban areas therefore hold promise for sustainable development because of their ability to support a large number of people while limiting their per capita impact on the natural environment (UNCHS 2001b).

Environmental problems occur because of the concentration of environmentally negative impacts. Good urban planning can reduce these impacts. Wellplanned, densely populated settlements can reduce the need for land conversion, provide opportunities for energy savings and make recycling more costeffective. If cities are properly managed, with adequate attention paid to social development and the environment, the problems present as a result of rapid urbanization, particularly in developing regions, can be avoided. A first step in this direction would be for national governments to incorporate a clear urban component in their economic and other policies.

Successes in urban environmental management include increases in resource efficiency, reductions in waste generation, improving urban infrastructure for water supply, the management and conservation of water resources in urban areas by improved waste water treatment and through legislation, setting up of recycling schemes, development of more effective waste collection systems, strict legislation for the treatment of hazardous waste, waste collection through public-private partnership, adoption of energy technologies by industry and households, and restoration of brownfields.