International housing boom hurting nature. .

A study co-authored by Stanford (Calif.) University associate professor of biological sciences Gretchen Daily concludes that the average household is shrinking--a global trend that is fueling an international housing boom which threatens the survival of plants and animals in dozens of countries, including the U.S. According to her research, housing units throughout the world are being built at a rate that outpaces population growth, resulting in a loss of habitat, natural resources, and biodiversity.

"We had hoped to find that, where human population growth was slowing, biodiversity might be given some breathing room," says Daily. "But instead, we've found that urban and suburban sprawl are accelerating faster than population growth is decelerating."

Throughout the world, the average number of people living together in a household is shrinking, primarily because of lower fertility rates, an increasing number of divorces, higher per capita income, aging populations, and a decline in multigenerational family units, the study notes. "Reduction in average household size takes a double toll on resource use and biodiversity. First, more households means mote housing units, thus generally increasing the amount of land and materials (for example, wood, concrete, and steel) needed for housing construction." Second, fewer people per household leads to higher per-capita consumption of water, fuel, land, and other natural resources, even when the size of the population declines. "This easily overlooked trend presents a particularly serious threat to...