• Urbanization is a byproduct of economic development.

As regions develop, more people move from rural areas to cities.

Within the last few years, more people are living in cities than in rural areas.

Many of the large cities will surpass 20 million by 2025; most of the world's megacities will be found in Asia.

• Dense living in large cities usually results in smaller per capita ecological footprints.

Most large cities exhibit smaller per capita carbon footprints than the national average.

• Urban sprawl occurs as people move away from urban centers to suburbs and exburbs.

Larger homes and longer commuting distances often result in larger ecological footprints.

Less dense living also reduces habitat for wildlife.

• As cities become congested, wealthier individuals move out to the suburbs.

Often this leaves a low-income inner city with heavy minority populations surrounded by wealthier suburbs of white populations.

Thus urban flight often becomes white flight.

• New urbanism neighborhoods are designed on a walkable, bike-friendly scale.

Mixed zoning allow a tight-knit neighborhood that places residential and commercial areas close together.

• The U.S. Green Building Council promotes buildings with reduced ecological footprints.

Its Leadership in Energy and Environmental Design certifies buildings that comply with its standards:

• use sustainable materials for building and furniture

• minimize energy use

• recycling wastes

• green roofs reduce runoff

• Greenbelts are corridors of connected parklands in urban areas.

In addition to open space that provide recreation areas, the South Bronx Greenway includes bikeways and green streets that provide alternative transportation options.

The forest preserves operated by counties around Chicago comprise the largest holding of locally owned public conservation land in the U.S.