them in poorer countries, generating huge new demands for goods and services and affordable shelter and housing and requiring faster economic growth and higher energy use. It is widely recognized that faster economic growth is the key to meeting the Millennium Development Goals by 2015. But if growth is not achieved in an environmentally sustainable way, its effect on poverty and human well-being will be disastrous.

      Economic development has led to dramatic improvements in the quality of life in developing countries, producing gains unparalleled in human history. But the gains have been unevenly distributed, and a large part of the world’s population remains desperately poor. Natural resources—land, water, and air—are being degraded at alarming rates in many countries. And environmental factors such as indoor and outdoor air pollution, waterborne diseases, and exposure to toxic chemicals threaten the health of millions of people. These concerns can be addressed by achieving the Millennium Development Goals.

     A healthy environment is an integral part of meeting the Millennium Development Goals, which call for integrating principles of sustainable development into country policies and programs and reversing environmental losses. The environmental Goal sets a target of halving by 2015 the proportion of people without sustainable access to safe drinking water and basic sanitation. It also calls for achieving a significant improvement in the lives of at least 100 million slum dwellers by 2020, bringing to fore the inadequacy of shelters and housing conditions in many poor countries (see table 3.a for selected indicators of housing conditions). All this requires measuring and monitoring the state of the environment and its changes—with better data on access to safe water and sanitation and a minimum set of indicators to monitor the conditions of shelters and housing. It also requires measuring and monitoring the links between economic growth and environmental change.

     Many such indicators are presented here. But despite greater awareness of the importance of environmental issues and efforts to improve environmental data, information on many aspects of the environment remains sparse. Data are often uneven in quality, cover different periods, and are sometimes out of date. The lack of adequate data hampers efforts to measure the state of the environment and to design sound policies. Many environmental indicators are not meaningful at the national level. Climate change has impacts that go beyond national boundaries. Environmental factors such as air and water pollution may have relevance only to the locality where they are measured. So global, regional, or city indicators (tables 3.11 and 3.13) are often more meaningful than national aggregates.

Indicators of economic growth and environmental change

     Human activity and economic growth affect the natural environment. In a chapter dedicated to environmental protection, the 2000 Millennium Declaration explicitly referenced climate change, desertification, biodiversity, and forest and water management and established a set of indicators to monitor the state of natural resources and to measure environmental change. Most of these indicators are covered in the tables in this section.

Forest coverage and protected areas. Forests are shrinking, and with them the diversity of the plants and animals they support. With growth and development, forests are being converted to agricultural land and urban areas. At the beginning of the 20th century the Earth had some 5 billion hectares of forested area. Now it has less than 4 billion hectares. The loss has been concentrated in developing countries, driven by the growing demand for timber and agricultural land, exacerbated by weak monitoring institutions. Low-income countries lost some 60 million hectares—about 7 percent of their forest—in the 1990s. By contrast, high-income countries reforested about 8 million hectares of forest in the same period (table 3.4).

     Closely linked to changes in land use is biodiversity, another important dimension of environmental sustainability. Many countries have designated a share of their land as protected areas (table 3.4). But even where protected areas have expanded and environmental regulations are respected, losses of biologically diverse areas cannot be reversed. About 12 percent of the world’s nearly 10,000 bird species are vulnerable or in immediate danger of extinction, 24 percent of 4,800 mammal species, and 30 percent of fish species.

Energy use and carbon dioxide emissions. Energy, especially electricity, is important in raising people’s standard of living. High-income countries use more than five times as much energy per capita as developing countries, and with only 15 percent of the world’s population they use more than half of its energy (table 3.7). Energy use and electricity generation also have environmental consequences. Generating energy from fossil fuels produces emissions of carbon dioxide, the main greenhouse gas contributing to global warming. Anthropogenic (human-caused) carbon dioxide emissions result primarily from fossil fuel combustion and cement manufacturing, with high-income countries contributing half (figure 3a and table 3.8). Among countries in all income groups, per capita emissions vary widely (from 22 tons in Kuwait and 20 tons in the United States to 0.016 tons in Chad). How energy is generated largely determines the environmental damage. Burning coal releases twice as much carbon dioxide as burning an equivalent amount of natural gas (see About the data for table 3.8, and table 3.9 for the sources of generating electricity).

Access to safe water and sanitation. While water supply and access to safe drinking water receive considerable attention at the international level, sanitation problems are seldom mentioned. Yet water supply issues are closely linked to sanitation. Evidence suggests that sanitation is at least as important as water supply in preventing diseases, and many of the health benefits from 

Source: Carbon Dioxide Information Analysis Center data

Source: United Nations Population Division 2004.

     The world is becoming increasingly urban. Urban areas are home to 48 percent of the world’s population—two of five people in low- and middle-income countries and almost four of five in high-income countries. Most of Latin America is as urbanized as Europe, with 77 percent of the population living in urban areas. Asia is urbanizing rapidly. Even such traditionally rural countries as China, India, and Indonesia now have hundreds of millions of people living in urban areas, with both the number of people and the share of the population in cities growing rapidly (table 3.10).

     In 1950 only 18 percent of people in developing countries lived in cities. In 2005 the proportion exceeded 40 percent, and by 2030 it is forecast to be 56 percent. Most future urban growth will be absorbed by urban centers in developing countries, which have a high average annual urban population growth rate of 2.2 percent, in contrast with the less than 1 percent rate in high-income economies.

Expanding cities serve many needs—with many consequences. Urbanization can yield important social benefits, improving access to public services such as education, health care, and cultural facilities (table 3.11). It can also lead to adverse environmental effects that require policy responses. Greater urbanization usually means greater pollution, which can overwhelm the natural capacities of air and water to absorb pollutants. The costs of controlling pollution can be enormous. And pollution exposes people to severe health hazards. Several major urban air pollutants—lead, sulfur dioxide, suspended particulate matter—are known to harm human health (table 3.13). A big source of urban air pollution is motor vehicles, whose numbers are strongly linked to rising income. The number of passenger cars increased from 16 cars per 1,000 people in 1990 to 27 in 2002 in developing countries and from 400 cars per 1,000 people to 440 in high-income countries, with New Zealand having the highest number, at 613, up from 438 in 1990 (table 3.12).

     While there is no evidence of a population threshold beyond which cities generate more negative than positive effects for their inhabitants, the rapid pace of population growth and enormous size of the population in many cities have overwhelmed the capacity of municipal authorities to respond. Millions of people in cities in developing countries cannot meet their basic needs for shelter, water, food, health, and education.

Demand for housing and emergence of the slums. Ever since there have been cities, there has been demand for housing and shelter and there have been poor living quarters. But only since the sixteenth century have there been slums—places that are “squalid, overcrowded, and wretched.”

     The unmet demand for affordable housing, along with urban poverty, has led to the emergence of slums in many poor countries. Slums have been the only large-scale solution to housing for low-income people. In cities, where competition for land and profits is intense, slums are the only type of housing that is affordable and accessible to most poor people.

     In 2001, 924 million people, or 31.6 percent of the world’s urban population, lived in slums (UN-HABITAT 2003). The majority were in developing economies, accounting for 43 percent of the urban population, with Sub-Saharan Africa having the largest proportion of the urban population living in slums (72 percent). The expected growth rate of the urban labor force far outpaces the rate of creation of formal sector urban jobs, so in all likelihood the majority of new urban residents will eke out a living in the informal economy and many will end up living in slums.

Most future urban growth will be absorbed by developing economies