In general, the carbon dioxide cycle works this way- plants pull CO2 out of the air, people or animals eat those plants, and then breathe CO2 back out. Before the industrial revolution, the amount of CO2 that was pulled out of the air, and the amount returning to it, was balanced. But now that we burn fossil fuels and cut down trees, we’ve dramatically increased our emissions.

Can we plant enough trees to soak up all of these emissions? The short answer is no. We just don’t have enough space. If we wanted to reverse climate change with trees, we’d have to grow an Amazon rainforest on approximately fifty percent of the surface of the earth. Trees do play an important role in soaking up carbon dioxide; they just can’t keep up with our emissions. It’s on us to stop burning fossil fuels and start getting our energy from renewable resources like wind and solar.

Megan Hall: Welcome to Possibly, where we take on huge problems like the future of our planet, and use science to find everyday solutions.

I’m Megan Hall. This question comes from John Bender, a reporter at The Public’s Radio. He wants to know– if CO2 causes climate change and trees use CO2 to grow, would it be possible to plant enough trees to reverse climate change?

We had Alina Kulman and Molly Magid from our Possibly team look into this question. Welcome Alina and Molly!

Alina Kulman: Hi Megan!

Molly Magid: Hello!

Megan Hall: So, what did you find out?

Alina Kulman: We talked with Stephen Porder, a professor of ecology at Brown University. He also happens to be a founder of this podcast.

Megan Hall: So what did he say about this question?

Molly Magid: Before the industrial revolution, the amount of CO2 that was pulled out of the air, and the amount returning to it, was balanced. 

Alina Kulman: In general, the cycle works this way- plants pull CO2 out of the air, and people or animals eat those plants, and breathe CO2 back out.

Molly Magid: But now that we burn fossil fuels and cut down trees, we’ve dramatically increased our emissions. 

Megan Hall: So could we plant enough trees to soak up all that extra carbon dioxide? 

Molly Magid: Stephen says that would just take up too much space. 

Stephen: You would need to grow essentially Amazon rainforest on about 50 percent

of the entire surface of the land.

Alina Kulman: And that would be just enough to deal with our past and current emissions. But we keep creating more every day.

Megan Hall: But what if we regrow some of the forests that we’ve cut down? Won’t that help?

Molly Magid: Forests do have a role to play. Since large scale agriculture moved to the midwest, New England forests have started to regrow and soak up more CO2.  But as our CO2 emissions rise, the trees just can’t keep up.

Alina Kulman: According to one study, if all of the tropical forests in Central and South America that were cut down were allowed to regrow for forty years, they would only soak up ONE year’s worth of carbon emissions.

Molly Magid: Stephen made this analogy:

Stephen: It’s like biking to work vs. flying to Australia If you’re gonna go fly to Australia, biking to work doesn’t make up for it.

Megan Hall: Ok, so if planting trees isn’t the solution, what is?

Alina Kulman: The problem is on us. We need to stop burning fossil fuels that create these emissions.

Molly Magid: That means we’ll have to get our energy from renewable sources like wind or solar

Megan Hall: Great! Thanks Alina and Molly! 

That’s it for today. For more information or to ask a question about the way you recycle, use energy, or make any other choice that affects the planet, go to “the public’s radio dot org slash possibly” 

Possibly is a co-production of the Institute at Brown for Environment and Society and the Public’s Radio. 

References

1. Chazdon, Robin L., et al. “Carbon Sequestration Potential of Second-Growth Forest Regeneration in the Latin American Tropics.” Science Advances, vol. 2, no. 5, May 2016, p. e1501639, doi:10.1126/sciadv.1501639.
2. Bastin, Jean-Francois, et al. “The Global Tree Restoration Potential.” Science, vol. 365, no. 6448, July 2019, p. 76, doi:10.1126/science.aax0848.

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