<P> Due to the larger area consumed by sprawling suburbs compared to urban neighborhoods, more farmland and wildlife habitats are displaced per resident . As forest cover is cleared and covered with impervious surfaces (concrete and asphalt) in the suburbs, rainfall is less effectively absorbed into the groundwater aquifers . This threatens both the quality and quantity of water supplies . Sprawl increases water pollution as rain water picks up gasoline, motor oil, heavy metals, and other pollutants in runoff from parking lots and roads . </P> <P> Gordon & Richardson have argued that the conversion of agricultural land to urban use is not a problem due to the increasing efficiency of agricultural production; they argue that aggregate agricultural production is still more than sufficient to meet global food needs despite the expansion of urban land use . </P> <P> Sprawl leads to increased driving, and increased driving leads to vehicle emissions that contribute to air pollution and its attendant negative impacts on human health . In addition, the reduced physical activity implied by increased automobile use has negative health consequences . Sprawl significantly predicts chronic medical conditions and health - related quality of life, but not mental health disorders . The American Journal of Public Health and the American Journal of Health Promotion, have both stated that there is a significant connection between sprawl, obesity, and hypertension . </P> <P> In the years following World War II, when vehicle ownership was becoming widespread, public health officials recommended the health benefits of suburbs due to soot and industrial fumes in the city center . However, air in modern suburbs is not necessarily cleaner than air in urban neighborhoods . In fact, the most polluted air is on crowded highways, where people in suburbs tend to spend more time . On average, suburban residents generate more per capita pollution and carbon emissions than their urban counterparts because of their increased driving . </P>

What discover allowed the decentralization of american cities