Land Use

The character of the environment has been largely dictated by the uses to which humans have put the land. Nomadic man walked lightly on the land, roaming from place to place, taking only what was needed for survival, leaving the land largely as it was. As humans settled into more sedentary, agrarian pursuits, they began to physically transform the land to meet their needs. Transformations of the land were generally localized, and environmental impacts were minimal. The ascent of mercantilism saw the growth of villages and towns in which goods and services were produced and traded in a more highly developed, social economy, in which production methods began to have wider environmental impacts. The 19th century saw an unprecedented intensification of land use, industrial-scale agriculture, and manufacturing that has transformed the land and regional environments almost beyond recognition. More importantly, the introduction of carbon-based fuels—wood and coal to power early industrialization, and petrochemical fuels of the 20th century—began to have transformative effects on the global climate.

Regional and global climates transform, and are transformed by, a complex dance of culture and economic development with nature. Over the past 20 years, humans have become increasingly aware of the extent to which land development is directly or indirectly responsible for the emission of numerous greenhouse gases—primarily carbon dioxide and methane—that act as forcing agents for global warming. These influences derive not only from the combustion-related emission of greenhouse gases and their accumulation in the atmosphere, but also from the local warming of the atmosphere by the urban heat island effect.

Since the 1990s, increasingly sophisticated computer models have demonstrated the tight coupling of changes in land use to subsequent changes in atmospheric and ocean temperatures. As virgin and agricultural land is transformed, attendant greenhouse gas emissions contribute to climate change at the global scale. Locally, the land’s albedo may decrease, resulting in the absorption of more of the sun’s radiant energy.

In densely developed urban environments, this leads to a heat island effect, which directly modifies local and regional climates. The 2007 Fourth Assessment Report from the Intergovernmental Panel on Climate Change recognized land-use and land use change as significant, if not primary, contributors to global climate change.

After World War II, the United States—and to a lesser extent the rest of the developed world— experienced a rapid growth in per capita income and the development of mass-market economies. Driven also by government policy (such as suburban mortgage subsidies, restriction of urban investment, urban flight, and the triumph of the automobile over transit in the United States) residential and commercial land-use development rapidly expanded outside existing urban boundaries to transform enormous swathes of undeveloped or agricultural land. The resulting low-density sprawl continues to drive—and, in turn, is driven by—the development of highway transportation infrastructure that encourages the growth of vehicle miles traveled and the attendant emission of carbon dioxide and other nonpoint source air pollutants.