Snapshots of our Urban Future.

Sometime in 2008, the United Nations predicts, we'll reach the point at which over half of the world's people live in urban areas. More than at any time in history, the fate of humanity, our economy, and the planet will be influenced by cities.

In the period from the Industrial Revolution through the 20th century, populations in Europe, North America, and then Japan passed the half-urban point. Most of the world's future population growth is expected to come in the rapidly growing cities of Africa and Asia, two regions that are set to become predominantly urban, and in Latin America, already 77 percent urban.

As urban numbers have grown, the ranks of the urban poor have surged as well. Of the 3 billion urban dwellers today, roughly 1 billion live in "slums," defined by UN-HABITAT as areas where people cannot secure one or more of these necessities: clean water, sanitation, sufficient living space, durable housing, or "secure tenure," which includes freedom from forced eviction.

In State of the World 2007: Our Urban Future, released in January, researchers find that urbanization is not only the defining demographic trend of our time, but also an important environmental phenomenon. Cities and suburbs are becoming the main human habitat. Although cities may strike us as unnatural landscapes--"concrete jungles" of buildings and pavement that supplant trees and grass--cities are in fact tied directly to nature, providing us with water, food, and shelter from the elements. Population growth may well cease in this century, but cities and their environmental pressures appear likely to expand.

Analyzing the links between cities and the environment, Kai Lee, a State of the World 2007 contributor, reviews evidence that the environmental challenges of urban areas vary with wealth. The poorest cities, and the poorest slums within them, tend to house the worst local hazards, such as disease spread by dirty water and lack of toilets. As a city industrializes, problems at the scale of the metropolitan area, such as air pollution from industry and traffic, tend to worsen at first and then improve as economic growth yields the resources to mandate cleaner technologies. However, a city's burden on the global environment tends to worsen with economic growth, as its residents are able to buy more cars, move into bigger houses that require more energy, and accumulate more stuff.

The stories that follow, excerpted from State of the World 2007, show how six cities are grappling with these trends. In sub-Saharan Lagos, Nigeria, local environmental threats are multiplying, as the government has proven unable to provide basic services to its population of more than 10 million. Other stories offer more hope. In rapidly industrializing China, home to some of the world's worst coal pollution, the small city of Rizhao has gone solar. Even with relatively low per capita income, Rizhao has spurred widespread use of solar hot water heaters, reducing coal use and improving air quality. And in a new section of Malmo, Sweden, high-income living takes less of a toll on the environment: all energy comes from local, renewable sources, and organic waste is re-used as biogas for cooking and to fuel vehicles.

For decades, many policymakers and environmentalists have looked at cities as the source of many problems, from the unhealthy living conditions of the urban poor to the air pollution that choked people of all income levels. But history has shown that cities can also generate solutions, which is why Jaime Lerner, the former mayor of a city known for its green urban design and planning (Curitiba, Brazil), writes in his foreword to State of the World 2007, "It is in our cities that we can make the most progress toward a more peaceful and balanced planet, so we can look at an urban world with optimism instead of fear."

--Molly O'Meara Sheehan, Worldwatch senior researcher and State of the World 2007 project director

CITYSCAPE:

LOJA, ECUADOR

An Ecological and Healthy City

When Jose Bolivar Castillo was elected mayor of Loja, Ecuador, in 1996, this impoverished Andean city of 160,000 was sprawling uncontrollably. Deforestation resulted in flooded rivers, and buses and cars burning leaded fuel polluted the air. Garbage filled the city's waterways, overflowed in collection bins, and overwhelmed a dumpsite across the street from the world-renowned Podocarpus National Park.

[ILLUSTRATION OMITTED]

[ILLUSTRATION OMITTED]

For Mayor Castillo, the inspiration to turn the city from an average Ecuadorian city into a "ciudad ecologica y salud-able"--an ecological and healthy city--came from within Loja itself: "I remember when I was a child, before the city became so polluted." In his eight years as mayor, Castillo worked with the municipality to implement policies that underscore the correlation between a healthy ecosystem, a healthy human population, and a healthy economy.

Comprehensive land-use planning and environmental policies at the county level limited degradation of the land, improved public health, and facilitated the management of necessary infrastructure--all while saving material and construction costs for important municipal projects like adding water lines to the poorest neighborhoods. As scientist Ermel Salinas explained, the water became drinkable "because our rivers have been cleaned up, protected, and are treated to United States ... requirements," preventing many illnesses caused by dirty drinking water.

A well-enforced ordinance required real estate developers to set aside 20 percent of their land for public open space, resulting in popular parks with multiple benefits. Architect Jorge Munos Alvarado, Loja's director of city planning, explained that the greenery "acts as a sponge by retaining stormwater, which prevents the rivers from flooding." And Humberto Tapia, director of public health, noted that exercising in parks reduces preventable illnesses such as obesity, diabetes, and heart disease.

The city's air quality improved following the use of cleaner public buses and the implementation of a new transportation policy mandating all cars to run on unleaded gas, with catalytic converters. Residents were also receptive to a new recycling program that required them to separate organic from inorganic trash every day, resulting in a 95 percent adherence rate. The municipality collected all city trash at least once daily and swept streets several times a day.

The benefits of...