Carpooling and recycling are good, easy ways to reduce your carbon footprint, but there are other ways to do it that may make your footprint a whole lot smaller.

For instance, having one fewer pair of small human feet padding around your home will do the trick.

At least those were the findings of a study published in the journal Environmental Research Letters. Looking at 39 peer-reviewed articles and governmental reports, the researchers determined that the best way to reduce your personal carbon emissions was to have one fewer child.

Adopting high-impact solutions

Most efforts at reducing your carbon footprint rely on easy lifestyle changes, like recycling, upgrading light bulbs and reducing your use of plastic bags. Such efforts, however, don't add up to a whole lot, according to the researchers.

For instance, the study's authors cite a textbook's recommendation of switching to reusable bags for shopping instead of relying on plastic bags to save 5 kilograms of carbon dioxide a year. That's helpful, the researchers acknowledge, but it's less than 1 percent as effective as a year without eating meat.

"Examples like this," the researchers write, "create the impression that the issue of climate change itself is trivial in nature, and represent missed opportunities to encourage serious engagement on high-impact actions."

Green salad with sweet potatoes, guacamole and olives Going vegan could help to reduce your personal carbon footprint. (Photo: Nina Firsova/Shutterstock)

These high-impact actions are what the researchers say can make a real difference, provided they're adopted on a societal level. That plant-based diet example they use in comparison to the plastic bag switch? It can result in a CO2 equivalents saving of 0.88 tonnes (0.88 tons) a year. The plant-based diet is also considered eight times more effective than upgrading your light bulbs.

A bigger savings can be found by eliminating car ownership. Living car-free, in the study representing all the emissions associated with the life cycle of owning a car, results in a 2.4-tonne CO2 savings a year. The researchers explain that using public transit can lower that savings if the person isn't walking or biking everywhere, but even eliminating a car and taking transit reduces emissions between 26 and 76 percent.

Baby bust

Perhaps most controversial, the researchers found that a U.S. family having one fewer child can reduce a parent's carbon footprint by 58 tonnes a year, or about the same reduction as having 684 teenagers engage in comprehensive recycling for the remainder of their lives.

This figure was determined by talking up the emissions of the child and all their descendants and then dividing that total by the parent's lifespan. Each parent received 50 percent the child's emissions, 25 percent of their grandchild's emissions and so on.

This may come off as a radical suggestion — have one fewer child — but the number of births in the U.S. has been declining for a number of years now. Provisional data about birth rates in 2017 published by the Centers for Disease Control in May 2018 dropped 2 percent compared to 2016, to 60.2 births per 1,000 women ages 15 to 4. This dip in birth rates continues a trend that started in 2008 following the Great Recession. While the reasons for the decline are almost certainly economic in nature, it could still lead to an environmental discussion.

A man holds a baby Not having another child could very well reduce this man's carbon footprint. (Photo: Flamingo Images/Shutterstock)

While the researchers acknowledge the idea of having one fewer child may be "politically unpopular," to them, it doesn't "justify a focus on moderate or low-impact actions at the expense of high-impact actions," like recycling or changing your light bulbs while still driving a gas-guzzling vehicle.

The idea that overpopulation is a cause of concern regarding the state of the environment isn't a new one, but it's one that may also be overblown, at least according to some. Lyman Stone, a regional population economics researcher and an agricultural economist at USDA, writes at Vox that a couple that doesn't have any children may still engage in activities that increase their carbon footprints to the same level as having a child.

"An American couple that forgoes a child might take an extra vacation, say, a road trip across Peru — burning extra fossil fuel for airfares and extra driving. The couple's plane ticket alone to Peru would produce between 3 and 7 metric-ton equivalents of CO2. Add in the couple's double consumption of housing (their home is vacant while they travel), their increase in driving (it's a road trip), their increase in eating and other consumption (it's vacation, after all) and that single vacation has about the same carbon impact as a baby in its first year (some 10 tons of carbon, let's estimate)."

For the record, the Environmental Research Letters study found that not taking one trans-Atlantic flight would reduce a person's carbon footprint by 1.6 tonnes.

A range of possible impacts

Group of kids collects recycling in a park For recycling to make a real impact, these kids would need to engage in a lifelong comprehensive program. (Photo: Rawpixel.com/Shutterstock)

As the example Stone uses above illustrates, shrinking one's carbon footprint is difficult, and conscious choices have to be made to do it.

Researchers are aware of this, advocating that textbooks shift away from advocating for the low-impact solutions, like plastic bag reduction, and put forth possible solutions that are more radical, or at the very least, will have a bigger impact.

"Though adolescents poised to establish lifelong patterns are an important target group for promoting high-impact actions, we find that ten high school science textbooks from Canada largely fail to mention [high-impact] actions (they account for 4 percent of their recommended actions), instead focusing on incremental changes with much smaller potential emissions reductions."

Of course, high impact and low impact choices can vary depending on where a person lives, something else the study points out.

For instance, switching from a gasoline automobile to an electric car still emits the equivalent of 1.15 tonnes of CO2 a year, but this number can go up if the electricity used in your area doesn't rely heavily on renewable sources of energy.

"We provide mean values for our recommended actions," the researchers write, "but we do not suggest that these are firm figures universally representative of each action, but instead best estimates."

Still, taking bigger swings to help the planet may have enough of a spillover effect to save it, the researchers believe. At least until we've all gone vegan and are walking everywhere.