We've all heard of ways to reduce our carbon footprint: biking to work, eating less meat, recycling.
But there's another way to help the climate. A recent study from Lund University in Sweden shows that the biggest way to reduce climate change is by having fewer children.
"I knew this was a sensitive topic to bring up," says study co-author Kimberly Nicholas on NPR's Morning Edition. "Certainly it's not my place as a scientist to dictate choices for other people. But I do think it is my place to do the analysis and report it fairly."
The study concludes that four high-impact ways to reduce CO2 gas emissions include having fewer children, living without a car, avoiding airplane travel and eating a vegetarian diet.
By the numbers, any of these lifestyle changes drastically reduce carbon emissions compared to more common practices like recycling, using energy-efficient light bulbs and line-drying clothes.
- having one fewer child (an average for developed countries of 58.6 metric ton CO2-equivalent (tCO2e) emission reductions per year;
- living car-free (2.4 tCO2e saved per year);
- avoiding airplane travel (1.6 tCO2e saved per round trip transatlantic flight); and
- eating a plant-based diet (0.8 tCO2e saved per year).
Nicholas says they also found that worldwide, many government resources on climate change did not focus on the top lifestyle changes in order to reduce carbon emissions.
"Something really important we found is that most government recommendations weren't really talking about what makes the biggest difference, and they weren't qualifying how big of a difference it made," Nicholas tells NPR's Steve Inskeep.
Many of the suggested changes need to be made on a large scale in order to have a substantial effect on climate change, but Nicholas says this study isn't meant to tell people how to plan their futures. (To calculate your carbon footprint, try the EPA's calculator.)
"I think the decision to become a parent is a really personal decision," she says. "I think the way people relate to it in terms of climate change depends on their view about climate change. If they don't believe or don't know the science, I feel like it makes them angry. I think if they do know the science and are overwhelmed by it, they feel guilt or despair."
There's already a word for this: climate trauma.
For some activists, climate change isn't only an intellectual problem. It's a "heart problem," says Josephine Ferorelli, co-founder of Conceivable Future. She spoke with NPR's Jennifer Ludden last year on having kids in the age of climate change last year. That story cited a study from 2010 that came to similar conclusions about the impact of slowing population growth on global carbon emissions.
But what about if potential parents know the science and want to raise their child on a healthy planet? Nicholas remains optimistic.
"Having a child in that case is a vote of hope," she says. "It's a vote that the world is going to be a better place and we can actually tackle this challenge."
Nicholas says in her own life, her and her fiancé are deciding if they want to cast that vote of hope for themselves.
"Because we care so much about climate change, it is a factor we're considering. But it's not the only one."