Do Trees Give off Carbon Dioxide? The Climate Facts

Humans could erase nearly 100 years worth of carbon emissions by planting a forest the size of the US and letting it mature. This was the conclusion of a study published in 2019 on how many trees the Earth could support as a way to halt climate change.¹ “Our study shows clearly that forest restoration is the best climate change solution available today”, said Tom Crowther, a researcher at ETH Zürich who conducted the study.²

Planting a forest of this size would cut atmospheric carbon dioxide by one quarter, the study found. But, some people worry that trees also give off carbon dioxide. However, how true is this? Could this turn into a problem?

Do trees release carbon dioxide (CO2)?

Trees release carbon dioxide into the air, just like humans do. But, they also take in a lot of CO2 and turn it into oxygen. Alternatively, they store it. The net result is that they are an extremely efficient way to quickly remove carbon dioxide from the air.³. This is why trees are critical for the future of our planet.

Leaves from plants and trees use the energy from sunlight to turn carbon dioxide in the air into organic matter. This process is called photosynthesis.⁴

In fact, the amount of carbon they absorb – mostly to build plant and tree structures – is more than the amount they release. In just one year, a mature tree can absorb more than 22 kilograms of carbon dioxide from the air and release oxygen in exchange. Moreover, the longer that trees live, the more mature they become, and therefore the more carbon dioxide they absorb.⁵

Since they are the most efficient way to reduce carbon dioxide in the air – which is heating up the planet – trees are vital in our efforts to stop climate change. 

Do trees breathe?

Trees take in oxygen and give out carbon dioxide, as humans do. But, you can’t technically call this breathing. Scientists call it respiration. Trees absorb oxygen through their cells, and they use it to create energy and carbon dioxide, as we do. This CO2 is then released back into the environment.⁶

But, the amount of carbon dioxide that trees emit is dwarfed by the amount they store. Some species of mature trees can absorb as much as 38 kilograms of carbon every year.⁷. It is also why scientists say we need far more trees to slow down climate change.

1. Bastin, J.-F., Finegold, Y., Garcia, C., Mollicone, D., Rezende, M., Routh, D., Zohner, C.M. and Crowther, T.W. (2019). The global tree restoration potential. Science, [online] 365(6448), pp.76–79. Available at: https://science.sciencemag.org/content/365/6448/76.
2. Environment. (2019). How to erase 100 years of carbon emissions? Plant trees. [online] Available at: https://www.nationalgeographic.com/environment/article/how-to-erase-100-years-carbon-emissions-plant-trees.
3. Pirates, C. (2019). How much Carbon does one Tree absorb? [online] CarbonPirates. Available at: https://www.carbonpirates.com/blog/how-much-carbon-do-trees-absorb/.
4. BBC (2019). What is photosynthesis? [online] BBC Bitesize. Available at: https://www.bbc.co.uk/bitesize/topics/zvrrd2p/articles/zn4sv9q.
5. Pirates, C. (2019). How much Carbon does one Tree absorb? [online] CarbonPirates. Available at: https://www.carbonpirates.com/blog/how-much-carbon-do-trees-absorb/.
6. Nature.com. (2010). Photosynthesis, Chloroplast | Learn Science at Scitable. [online] Available at: https://www.nature.com/scitable/topicpage/photosynthetic-cells-14025371/.
7. Villazon, L. (2019). How many trees does it take to produce oxygen for one person? [online] BBC Science Focus Magazine. Available at: https://www.sciencefocus.com/planet-earth/how-many-trees-does-it-take-to-produce-oxygen-for-one-person/.