How do trees affect global warming?

how do trees affect global warming

Forests are the ‘green lungs’ of our planet. Without trees, life on Earth would look very different. In addition to producing clean air and oxygen, trees keep the climate of our planet stable through the removal carbon dioxide (CO2). So how do trees affect global warming?

What is Carbon Dioxide? Why is it important?

Carbon dioxide is a greenhouse gas that has been historically linked across the world with all the key heating events in Earth’s history1. Human activities such as industry and deforestation have caused a rise in CO2 emissions to almost double pre-industrial levels. Today, CO2 levels sit at just over 400 parts per million (ppm), whereas before the Industrial Revolution started in the mid-1700s, the global average amount of carbon dioxide was about 280 ppm. Alongside this rise in CO2, global average temperatures have been steadily increasing3 and are now widely accepted by the scientific community to be the leading cause of climate change.

More than 75% of biomass is stored in forests globally4. In other words, trees are very good at storing carbon and are now being used as an important tool in the fight to limit global warming to 2°C above pre-industrial average temperatures. As part of the Paris Climate Agreement (2016)5, countries across the world pledged to protect existing forests and plant more trees. The UK alone has pledged to plant 11 million trees by 20226.

Why is deforestation a problem?

It is key to remember that trees can only store carbon whilst they are still alive. When trees die, breakdown and begin to decompose, organic carbon is re-released as carbon dioxide gas.

Trees remove carbon dioxide during the process of photosynthesis. This is the production of glucose from carbon dioxide and water which releases the waste product oxygen. Therefore, trees reduce the effects of global warming by removing carbon dioxide from the atmosphere and storing it as organic carbon.

The tropical wildfires of Brazil in 2019, where thousands of fires raged in the Southern Amazon basin, were a stark and devastating reminder of how we are struggling to protect our ancient forests. Bolsonaro encouraged loggers and farmers to clear the land to further his own agenda, one that does not align with conserving the forest or its communities7, although weather data suggests the intensity and ferocity of these fires was aggravated by a prolonged period of drought. An estimated 104-141 million tonnes of carbon dioxide8 were released into the atmosphere during this period. For some perspective, this is just under the amount of total carbon emissions for the whole of the UK in 20189.

Further importance of trees

Trees play a much larger role in global warming than simply how much carbon they store. They have massive importance in almost all cultures worldwide and have become a symbol shaping the idea of a ‘green’ revolution. Forests also play a large part in our mental and physical health, providing clean air and stimulation that researchers have found to relieve stress10. From an environmental point of view, trees help keep water clean, prevent flooding and provide ecological diversity.

In answer to the question how do trees affect global warming?, in the shortest and truest conclusion possible, trees help us to live healthy lives and help our planet breathe.


Even though trees play an important role in our environment, they are not the only solution. We will not be able to save the planet just by making sure we protect the forests. In order to face the climate catastrophe, we must drastically reduce carbon emissions from fossil fuels AND protect existing forests. 


1 Gregory J. Retallack. (2002). Carbon dioxide and climate over the past 300Myr. Royal Society. 360 (1793).
2 Lindsey, R., 2020. Climate Change: Atmospheric Carbon Dioxide | NOAA Climate.Gov. Available at: <> [Accessed 16 April 2020].

3 Herring, D., 2013. Global Warming Frequently Asked Questions. [online] Available at: <> [Accessed 16 April 2020]

Reichstein, Mark and Carvalhais, Nuno. Aspects of Forest Biomass in the Earth System: Its Role and Major Unknowns. Surveys in Geophysics. Published July 9, 2019. Accessed November 2, 2020.

5 “Paris Agreement”. United Nations Treaty Collection. 8 July 2016. Archived from the original on 21 August 2016. Retrieved 16/04/2020.

6 GOV.UK. 2019. Government Launches New Scheme To Boost Tree-Planting. [online] Available at: <> [Accessed 16 April 2020].

7BBC News. 2019. Amazon Fires ‘Increase 84% In One Year’. [online] Available at> [Accessed 16 April 2020].

8 Grant, M., 2020. New Data: Brazilian Amazon Fires Have Released 104-141 Million Metric Tons Of CO2. [online] Woods Hole Research Center. Available at: <> [Accessed 16 April 2020].

9 Department for Business, Energy & Industrial Strategy, 2020. 2018 UK Greenhouse Gas Emissions, Final Figures. [online] National Statistics, p.1. Available at: <> [Accessed 16 April 2020].

10 Ward Thompson, C., Roe, J., Aspinall, P.A., Mitchell, R., Clow, A. & Miller, D. (2012) ‘More green space is linked to less stress in deprived communities: Evidence from salivary cortisol patterns’ Landscape and Urban Planning vol 105, no. 3,pp. 221–229

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