Over half of humans now live in cities. Environmental scientists have often criticized cities for expanding into farmland and for their tremendous consumption of energy, water, food, concrete, and land. But the environmental cost per person is usually lower for urban living than for suburban or rural living, especially in wealthy countries. Because they are compact, cities require fewer miles of roads, water and sewer lines, less heating, and fewer private cars per household. Because distances are shorter, roads and utility infrastructure are shared, apartments or row houses share heat, and public transportation reduces the need for driving to work. Polluted cities can be unhealthy, but well organized cities can provide cultural resources and preserve environmental resources in many beneficial ways.
High-density areas can afford to support reliable, efficient transit systems, where many riders share the cost of getting around, such as this bus-rapid transit system in Curitiba, Brazil. Public transit uses far less space, energy, and materials than does private travel. Furthermore it decreases the levels of pollution caused by the usage of commuter vehicles.
Safe walking and bike routesFreedom from dependence on cars increases mobility for young people, old people, and others without cars. Cities with separated walk-ways and bikeways are friendly for children and families; they also provide exercise and save money.
Compact building A compact urban design greatly increases efficiency of land use, reduces transit distances, and increases heating or cooling efficiency, as buildings share walls. Reduced dependence on cars, and car sharing, can help control the problem of parking shortages.
Mixed-use planning Integrating housing with shopping, entertainment, and office space provides jobs and services where people live. These neighborhoods can encourage walking and build community, as people spend less time in travel to shopping and work.
Green space Recreational space has physical and emotional benefits for urban residents. Living vegetation and soils cool the local microclimate, store nutrients and moisture, and provide habitat for birds and other wildlife.
Recycling programs Recycling collection is easiest where transportation is minimal and where recyclable materials are abundant. Recycle bins present in bins in Kuala Lumpur, Malaysia accept all kinds of recyclables.
Green infrastructure New techniques moderate the impact of impervious surfaces, including permeable pavement, green roofs, and better building design. A “green” parking lot in Chengdu, China supports both traffic and vegetation, allowing rainfall to percolate into the ground.
Energy efficiency Alternative energy is easier to use right at the source. Rooftop solar energy, district heating, and other strategies aid efficiency.Biomass-burning plant in Copenhagen, and others like it, provide nearly all heating for Denmark’s major cities.
Local farm economies are more viable if farmers can sell direct to consumers—something that is much easier where there are lots of buyers in one place. Cities have become an essential income source for many produce farmers.
Farmland conservation Sprawling suburbs gobble up farmland, woodlands, and wetlands. This is the fastest type of land-use change in most developing countries. Compact cities minimize destruction of farmland, habitat, recreational space, and watersheds