Researchers Find That Carbon Dioxide Does Not Boost Forest Growth

Join Our Community of Science Lovers!

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Levels of atmospheric carbon dioxide, a potent greenhouse gas, have been on the upswing over the last century. How the earth's plant life, particularly trees, will react to the change remains unclear. Some researchers have proposed, however, that the rising concentrations will spur plant growth and thus allow them to store additional amounts of carbon dioxide, thereby mitigating the atmospheric increase to some degree. Now a report published in the journal Science disputes this claim. A four-year study of a forest in Switzerland indicates that additional carbon dioxide does not boost tree growth.

A team of researchers led by Christian Korner of the University of Basel sprayed a 500-square-meter patch of deciduous forest with excess carbon dioxide for four years. The mature trees within it were exposed to two tons of extra carbon dioxide each day during the six-month-long growing season, giving them access to almost 50 percent more of the gas than is currently in the atmosphere. Overall, there was no increase in stem growth or leaf production during the study period, although the trees did cycle carbon dioxide and rerelease in to the air more quickly. It turns out not all species reacted in the same way to the excess carbon dioxide, revealing a flaw in earlier studies that focused on a single species.

The new experiment still has drawbacks, its planners note, making it a "compromise between realism and precision." For one, the timescale may still be too short to fully understand the effects of increased carbon dioxide. It is also possible that belowground growth of root systems could potentially store additional carbon in the soil. Future work will need to ascertain whether the new results apply to conifers and tropical trees, among other varieties.

It’s Time to Stand Up for Science

If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.

I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.

If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.

In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.

There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.

Thank you,

David M. Ewalt, Editor in Chief, Scientific American