Jim Bob and Michelle Duggar, stars of the TLC show (currently) titled 18 Kids and Counting, just announced that they are expecting the 19th addition to their family. This enthusiastic rate of reproduction is in keeping with the family's religious convictions. The Duggars follow the tenets of the Quiverfull movement, a sector of Christianity that believes in following the biblical exhortation to have many children.

But the Duggars aren't the only ones affected by the choice to supersize their family. The world will also have to make room for this 19th child and his descendants. And according to recent research, having lots of kids may have a much bigger impact on the environment than previously thought.

Here's why:

Oregon State University researchers say that if you're serious about reducing your carbon footprint, the best way to do it is to have one less child. They claim the effect is almost 20 times greater than recycling, driving a high-mileage car, or using energy-efficient appliances and light bulbs over your entire lifetime. So even if Duggar No. 19 becomes the next Al Gore, he'll still contribute to the eventual disappearance of the Maldives.

Americans and other citizens of developed countries are a particularly big drain on the planet's resources. A 2007 study by Washington State University researcher Eugene A. Rosa found that the principal factors affecting climate change are growth of human population and consumption. And, "The effect is much higher in developed nations than in under-developed nations," Rosa says. "For instance, the ecological footprint of the U.S. is about 20 times that of a country like Bangladesh."

And finally, more people can lead to larger rodents. One group of researchers studied the evolution of white-footed mice in the Chicago area from 1855 to 2003 and found "dramatic changes in total length, with broader, longer noses and longer but shallower skulls," which the researchers said was likely caused by the large environmental changes occurring over time. This study led another researcher to look at the changes in the head shape and overall size of rodents as they relate to human population density and climate change. "Our results indicate that over the last 100+ years, rapid morphological change in rodents has occurred quite frequently...Our results also suggest that these changes may be driven, at least in part, by human population growth and climate change," the authors wrote.

While no one is suggesting that we blame the Duggars for an increase in giant rats, news of their latest addition has touched a nerve in the environmental community and elsewhere. Scripps News columnist Bonnie Erbe suggests that just as the Duggars use the media to promote their multitudinous family, "others should use the same bully pulpit to teach the Duggars what they are doing has a negative impact on their fellow citizens." And the iVillage community comments ranged from criticism over what's perceived as excessive child bearing to support for what may be a greener lifestyle than most. "For the most part, all of the large families I know...actually are more environmentally conscious then families with one or two children," says iVillager cl-trghig. "I will be honest that, for the most part, their environmental consciousness comes from being frugal, but they still reuse and recycle more things and items then most of the smaller families I know."

This isn't the first time Quiverfull families like the Duggars have faced tough questions about whether it's irresponsible to have so many kids. "[Quivers] acknowledge the criticism that having a large family exponentially increases their carbon footprint, but they tend to turn that around and say, yes, it might be a larger family, but living in this larger family encourages them to live more simply than most Americans and they don't end up using as many resources," says Kathryn Joyce, author of Quiverfull: Inside the Christian Patriarchy Movement, who has written about the Duggars.

Of course there's no way to know whether the Duggars kids have a smaller ecological footprint than the average American child. Though if each of the 19 Duggar kids also pursue the same philosophy as their parents and have 19 of their own children, it's possible that the prolific Mr. and Mrs. Duggar could be responsible for 380 new people on the planet. And big or small, that's a lot of footprints.

To find out how big your carbon footprint is, go to MyFootprint.org

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