Do Trees Need Carbon Dioxide?

Scientists have long wondered how trees adapt to changing temperatures and how much carbon dioxide they need. In 2016, a study found that forests may deal with rising global temperatures by contributing less CO2 to the atmosphere than previously thought.¹

‌But, we still don’t know enough about trees and how they use and need carbon dioxide.

Do trees need carbon dioxide to survive?

Trees don’t need CO2 to breathe, but for energy and building themselves. They absorb CO2 using photosynthesis and convert it into carbohydrates, which are then used to build their leaves, trunks, and stem.² ‌In other words, trees need carbon dioxide to survive because the carbon, hydrogen, and oxygen molecules created through photosynthesis make up around 96 percent of the total dry mass of a typical plant. Without carbon, the plant or tree would die.³

Some use this fact to argue that rising CO2 levels in the air would be beneficial for trees. But this is no excuse to downplay or even welcome global warming. Carbon dioxide levels in the atmosphere are much higher than they have been for thousands of years. Higher CO2 levels cause global warming and are destabilising our climate.⁴

Do trees produce more oxygen than carbon dioxide?

Trees have an amazing capacity to produce and absorb CO2 at the same time. During photosynthesis, they absorb CO2 and water to create energy and oxygen. But they also respire like others, using energy and oxygen to create carbon dioxide and water.⁵

‌So, whether trees produce more oxygen than CO2 depends on their species, local weather, and characteristics. In some cases, forests can be net emitters of CO2. In other regions, they absorb more carbon than they produce.⁶

‌But scientists are increasingly concerned that tropical forests are losing their ability to remove CO2 from the atmosphere. This could be down to forests shrinking in size and rising global temperatures. One study found that the Amazon rainforests could become a net emitter of carbon in 15 years.⁷

Trees are still the best way that we know of to remove carbon dioxide from the air. Without them, CO2 levels would be far higher, and the Earth would tip into runaway climate change much faster. “Without them, we lose extraordinary and essential functions for life on Earth.”⁸

1. Schlossberg, T. (2016). Trees Deal With Climate Change Better Than Expected. The New York Times. [online] 16 Mar. Available at: https://www.nytimes.com/2016/03/16/science/global-warming-climate-change-trees-carbon-dioxide.html [Accessed 14 Apr. 2021].
2. Bassham, J.A. and Lambers, H. (2019). photosynthesis | Importance, Process, & Reactions. In: Encyclopædia Britannica. [online] Available at: https://www.britannica.com/science/photosynthesis.
3. Taub, D. (2010). Effects of Rising Atmospheric Concentrations of Carbon Dioxide on Plants | Learn Science at Scitable. [online] Nature.com. Available at: https://www.nature.com/scitable/knowledge/library/effects-of-rising-atmospheric-concentrations-of-carbon-13254108/.
4. Smith, B., Cuntz, M., Canadell, P. and Haverd, V. (2020). Yes, more carbon dioxide in the atmosphere helps plants grow, but it’s no excuse to downplay climate change. [online] The Conversation. Available at: https://theconversation.com/yes-more-carbon-dioxide-in-the-atmosphere-helps-plants-grow-but-its-no-excuse-to-downplay-climate-change-130603.
5. BBC Bitesize. (2019). Photosynthesis – Revision 3 – KS3 Biology – BBC Bitesize. [online] Available at: https://www.bbc.co.uk/bitesize/guides/zpwmxnb/revision/3.
6. unece.org. (n.d.). Carbon Sinks and Sequestration | UNECE. [online] Available at: https://unece.org/forests/carbon-sinks-and-sequestration.
7. Vaughan, A. (2020). Net-zero emissions target in peril as tropical forests absorb less CO2. [online] New Scientist. Available at: https://www.newscientist.com/article/2236228-net-zero-emissions-target-in-peril-as-tropical-forests-absorb-less-co2/ [Accessed 14 Apr. 2021].
8. Nuwer, R. (2019). What would happen if all the world’s trees disappeared? [online] Bbc.com. Available at: https://www.bbc.com/future/article/20190911-what-would-happen-if-all-the-worlds-trees-disappeared.