Urban Development

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In the last 200 years the percentage of the U.S. population living in cities increased from 5 percent to almost 80 percent. Th is increase in urban population has also caused more urban sprawl. Urban sprawl is defi ned as the growth of human populations in areas that previously had low population density. Such outward spread results when people feel the need for more space, safer neighborhoods, aff ordable housing, and, ironically, a place where they can live closer to nature. Of course, urban sprawl usually destroys natural habitat by reducing woodlands, grasslands, desert, or wetlands. Urban sprawl also fragments habitat and pollutes it, increases the incidence of wildlife killed on roads, and increases soil erosion, which begins a breakdown of many ecosystems.

Th e spread of human populations is unlike population growth and decline in the natural world. Animals and plants adjust their birthrate in conjunction with resource availability, but people do not do the same when they build cities higher and farther. If people continue consuming resources with little regard for the future, the environment may reach a point at which it cannot sustain the number of people on Earth. Al Gore wrote in An Inconvenient Truth, “. . . death rates and birth rates are going down everywhere in the world, and families, on average, are getting smaller. But even though these hoped-for developments have been taking place more rapidly than anyone would have anticipated a few decades ago, the momentum in world population has built up so powerfully that the ‘explosion’ is still taking place and continues to transform our relationship to the planet.” More than twice as many people live on Earth today than lived here in 1950, when the earliest environmental laws were passed.

Populations with fast growth rates contain the fastest-growing urban centers; China and India provide examples of rapid urbanization. These two countries account for more than one-third of the world’s total population growth and, though most of their populations live in rural areas, both have very large rural-to-urban migrations. China and India each will soon reach a milestone that the world achieved in 2007: for the first time ever, more people live in cities than in rural areas.

Developing countries in 2007 had twice the birthrate per 100,000 people (22.1) than developed countries (11.0), and their populations increase at about 1.4 percent a year. Developing countries also possess a disproportionate amount of the world’s plant and animal diversity. The economies of developing countries are also growing quickly, signaling increases in urban centers, housing, and roads, which all threaten habitat. Booming economies also cause secondary effects on the environment: expansion of agricultural monoculture, air and water pollution, and noise and light
pollution. Despite the economic growth in developing countries, a large number of people still live in poverty in these places—people who feel they must harvest their natural resources for income. This combination of increasing economic growth with widespread poverty has had a crippling effect on biodiversity.

Part of the Biodiversity Treaty addresses the needs of developing nations while at the same time addressing biodiversity loss. The treaty made provisions for compensating developing nations so that their citizens would not be forced to destroy native plants and animals for food or income. Though the treaty may be flawed in some people’s minds, it represented an important step by calling for cooperation from more than 150 nations to preserve biodiversity in all parts of the world, not just within national boundaries.