After decades of fretting about population explosion, scientists are pointing to a long-term hidden global menace.
The household. More specifically, the household explosion.
In the current edition of Population and Environment, Jianguo “Jack” Liu, director of the Michigan State University Center for Systems Integration and Sustainability, and former MSU students Mason Bradbury and Nils Peterson present the first long-term historical look at global shifts in how people live. One large shelter for many people is giving way across the world to ones holding fewer people – sometimes young singles, sometimes empty nesters, and sometimes just folks more enamored with privacy.
Liu and his colleagues pointed out that even though population growth has been curbed, the propensity to live in smaller households is ratcheting up the impact on the natural resources and the environment worldwide.
“Long-term dynamics in human population size as well as their causes and impacts have been well documented,” said Liu, who is the Rachel Carson Chair in Sustainability. “But little attention has been paid to long-term trends in the numbers of households, even though they are basic consumption units.”
More houses require more lumber and other building materials. Smaller homes are generally less efficient, with fewer people using proportionally more energy, land and water.
Reviewing data dating back 400 years, the researchers revealed that household size has been declining in some countries for centuries, adding a largely unaccounted for nuance to human’s impact on the environment. In this paper, Liu and his colleagues call for households to be more centrally included in calculating human’s impact on the environment. They also caution against thinking that slowing population growth is cause for celebration.
Average household size in developed countries declined rapidly from approximately 5 members in 1893 to 2.5 at present, while the rapid decline in average size in developing nations began around 1987. The number of households grew faster than population size in almost every country and every time.
“We’ve documented that the changes we’re seeing in household size across the globe essentially doubles the number of homes needed per-capita,” said Peterson, who is now with North Carolina State University. “This will put enormous strain on the environmental life support system we rely on, even if we achieve a state of zero population growth.”
The researchers point out that the environmental footprint becomes more of a trail. The new homes usually eventually require more roads, more yards and more commercial development.
Bradbury is a master’s student at the University of Montana.
The research is supported by the National Science Foundation, MSU and NCSU.