Reuters

Having children is the surest way to send your carbon footprint soaring, according to a new study from statisticians at Oregon State University.

The study found that having a child has an impact that far outweighs that of other energy-saving behaviors.

Take, for example, a hypothetical American woman who switches to a more fuel-efficient car, drives less, recycles, installs more efficient light bulbs, and replaces her refrigerator and windows with energy-saving models. If she had two children, the researchers found, her carbon legacy would eventually rise to nearly 40 times what she had saved by those actions.

“Clearly, the potential savings from reduced reproduction are huge compared to the savings that can be achieved by changes in lifestyle,” the report states.

The impact of children varies dramatically depending on geography: An American woman who has a baby will generate nearly seven times the carbon footprint of that of a Chinese woman who has a child, the study found.

The calculations take account of the fact that each child is, in turn, likely to have more children. And because the calculations derive from the fertility rate — the expected number of children per woman in various countries — the findings focus on women, although clearly men participate in the decision to have children.

“In discussions about climate change, we tend to focus on the carbon emissions of an individual over his or her lifetime,” said Paul Murtaugh, a professor of statistics at O.S.U., in a statement accompanying the study’s release. “Those are important issues and it’s essential that they should be considered. But an added challenge facing us is continuing population growth and increasing global consumption of resources.”

The full report is published in the February 2009 edition of the journal Global Environmental Change: Human and Policy Dimensions.