2021: What Role Do Trees Play in Today’s Global Warming?

The main cause of climate change is the combustion of fossil fuels, such as oil, coal and natural gas.¹ They release greenhouse gases, such as carbon dioxide (CO2), which trap heat in the Earth’s atmosphere.² This begs the question, what role do trees play in today’s global warming?

To stop climate change, we must stop burning fossil fuels. Also, trees are considered to be central to fighting climate change.³ Understanding the connection between CO2 and trees is crucial to establish what role trees play in today’s global warming. 

Tree planting in 2021

Many countries around the world are committed to planting trees to prevent global warming. This year, the Ugandan Ministry of Water and Environment is organising a national reforestation campaign, Running Out of Trees (ROOTs).⁴

In the UK, the government is pledging GBP £2.7 million to increase tree planting and natural regeneration.⁵ Even oil-producing Saudi Arabia wants to plant 10 billion trees and increase the country’s tree cover 12-fold.⁶

How do trees help the environment?

Trees help the environment in many different ways. When it comes to combatting climate change, they are “our most powerful weapon”.⁷ This is largely due to their role in the carbon cycle. A firm grasp on the connection between CO2, climate change and trees is central to any insight on what role trees play in today’s global warming.

All plants pull CO2 from the air in the process of photosynthesis.⁸ They use water, sunlight and carbon to form sugars.⁹ Plants and trees use these sugars to grow. They simultaneously absorb carbon into their stems, trunks, branches, leaves and roots.¹⁰

Any excess carbon they do not use is sequestered in the plant’s biomass and the surrounding soil.¹¹ Thanks to this natural process, the Earth’s forests and soil soak up about 30 per cent of atmospheric carbon emissions.¹²

Greenhouse gases and tree planting

This is extremely important since CO2 is the primary greenhouse gas. Humans have increased the concentration of CO2 in the atmosphere by 47 per cent since pre-industrial times. It is the most important long term driver of climate change.¹³ Since the Industrial Revolution, humans have increased the Earth’s average temperature by 1.0°C.¹⁴

How many trees would we need to plant to stop global warming?

There is no figure for the number of trees needed to stop global warming. The planet’s temperature will continue to increase until we stop burning fossil fuels and causing greenhouse gas emissions.¹⁵ Tree planting can help to mitigate the effects of climate change by removing CO2 from the atmosphere. However, we must also put an end to human activity that destroys our existing forests and stop using coal, oil and gas to prevent global warming.

One study has researched how many additional trees the Earth’s landmass could support. They found that “ecosystems could support an additional 0.9 billion hectares of continuous forest”. This represents an increase in forest area of more than 25 per cent. It could also reduce the atmospheric carbon by a quarter.¹⁶ 

Yet, even these ambitious findings do not claim tree planting alone can solve climate change. Any theory that relies on planting trees alone, without reducing fossil fuel usage, fails to appreciate what role trees play in today’s global warming.

Planting trees: How efficient is it to reduce global warming?

Planting more trees does help to prevent climate change. It is one of the best climate solutions. Initiatives to plant one trillion trees and realise these goals are continuing throughout 2021.¹⁷ The non-profit organisation One Tree Planted managed to plant over 10 million trees in 25 countries last year, despite the COVID-19 pandemic. In 2021, they aim to plant 13.5 million trees. Their projects include afforesting Indonesia’s Lampung region.

This area has experienced “profound deforestation, damaged soils, contaminated water bodies, and erosion” because of deforestation. Planting 100,000 trees will help to revitalise the area and prevent further encroachment and damage to national parks.¹⁸

Similarly, the African Great Green Wall is receiving at least USD $14.326 billion in new funding in 2021.¹⁹ The ambitious project aims to prevent the encroaching of the Sahara desert, restore 100 million hectares of degraded land and create 10 million green jobs by planting trees.²⁰ But tree planting projects alone cannot stop global warming. 

What are five benefits of planting and caring for our trees?

1. Trees absorb and store carbon dioxide

A mature tree captures on average about 22 kilograms (kg) of CO2 per year through photosynthesis.²¹ Thanks to this, the world’s forests and agriculture can get us at least a quarter of the way to meeting the 1.5°C goal of the Paris Agreement.²²

2. Trees prevent soil erosion

Topsoil is critical for all life on Earth. 95 per cent of the world’s food grows in the uppermost layer of soil.²³ However, half of the world’s topsoil has been lost in the past 150 years.²⁴ The cost to global GDP is about USD $8 billion.²⁵ 

Trees serve as a windbreak and stop loose soil from being blown away. Their foliage protects soil from heavy rainfall. Likewise, deep roots hold the soil in place and aid water drainage.²⁶

3. The leaves of trees intercept pollution and clean our air²⁷ 

By trapping toxic pollutants, such as nitrogen dioxide, and harmful microscopic particles from diesel vehicles and other fumes, trees improve the air we inhale.²⁸ This benefit should not be underestimated. Nine out of 10 people breathe air containing high levels of pollutants. The WHO estimates about seven million people die annually from exposure to polluted air.²⁹

4. Indigenous trees are critical for biodiversity

For example, a single native UK oak tree can harbour 284 insect species. In contrast, just four insects will reside in non-native horse chestnut trees.³⁰ Forests support an incredible 80 per cent of all land-based species.³¹ Biodiversity is important because the loss of any single species can have disastrous effects on the wider ecosystem.

5. Trees also mitigate flooding

Their leaves and branches intercept rainfall. Raindrops falling on leaves are more likely to evaporate back into the air. This slows the rate that water flows into rivers, reducing the possibility of it bursting its banks.³² Climate change increases the likelihood of extreme rainfall.³³ Trees’ role in preventing flooding is, therefore, more important than ever.

Can we live without trees?

In short, no – we cannot live without trees. Even if they did not provide all of the incredibly useful benefits already mentioned, we would still need trees for one crucial reason. They produce oxygen. Rainforests alone account for 28 per cent of the oxygen in the atmosphere.³⁴

Oxygen is a byproduct of photosynthesis. For example, for every glucose molecule that a tree makes, six carbon atoms are stored and six molecules of oxygen are released. A mature 12-metre tall sycamore tree that grows five per cent each year will store 38kg of carbon and release 100kg of oxygen in the process.³⁵ A large tree can provide roughly a day’s supply of oxygen for up to four people, according to the US Department for Agriculture.³⁶ Even in 2021, we cannot hope to replicate the benefits that planting more trees brings.

We are clearly dependent on trees for the sake of our planet and for life itself. They produce our oxygen and make our air cleaner to breathe. Likewise, forests absorb about 30 per cent of climate change-causing emissions.³⁷ The science is clear. If there were ever any doubts about what role trees play in today’s global warming and climate solutions, it should be evident that they are crucial to limiting global warming to 1.5°C.

1. Met Office (2019). Causes of climate change. [online] Met Office. Available at: https://www.metoffice.gov.uk/weather/climate-change/causes-of-climate-change.
2. NASA (2018). The Causes of Climate Change. [online] Climate Change: Vital Signs of the Planet. Available at: https://climate.nasa.gov/causes/.
3. Carrington, D. (2019). Tree planting “has mind-blowing potential” to tackle climate crisis. [online] the Guardian. Available at: https://www.theguardian.com/environment/2019/jul/04/planting-billions-trees-best-tackle-climate-crisis-scientists-canopy-emissions.
4. Afrik 21. (2021). UGANDA: 2021 Roots aims to plant 40 million trees. [online] Available at: https://www.afrik21.africa/en/uganda-2021-roots-aims-to-plant-40-million-trees/ [Accessed 13 Apr. 2021].
5. GOV.UK. (2021). eAlert 12 March 2021 – New tree fund for local communities. [online] Available at: https://www.gov.uk/government/publications/ealert-12-march-2021-new-tree-fund-for-local-communities/ealert-12-march-2021-new-tree-fund-for-local-communities [Accessed 13 Apr. 2021].
6. www.spa.gov.sa. (2021). HRH Crown Prince Announces: “The Saudi Green Initiative and The Middle East Green Initiative” The official Saudi Press Agency. [online] Available at: https://www.spa.gov.sa/viewstory.php?lang=en&newsid=2208375 [Accessed 13 Apr. 2021].
7. Trust, W. (n.d.). How Trees Fight Climate Change. [online] Woodland Trust. Available at: https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/british-trees/how-trees-fight-climate-change/.
8. State of the Planet. (2018). Can Removing Carbon From the Atmosphere Save Us From Climate Catastrophe? [online] Available at: https://blogs.ei.columbia.edu/2018/11/27/carbon-dioxide-removal-climate-change/ [Accessed 13 Apr. 2021].
9. National Geographic Society (2019). Photosynthesis. [online] National Geographic Society. Available at: https://www.nationalgeographic.org/encyclopedia/photosynthesis/.
10. Forests, C.T. (2020). Technical Note – How do Trees Store Carbon? [online] Creating Tomorrow’s Forests. Available at: https://creatingtomorrowsforests.co.uk/blogs/news/technical-note-how-do-trees-store-carbon.
11. Forests, C.T. (2020). Technical Note – How do Trees Store Carbon? [online] Creating Tomorrow’s Forests. Available at: https://creatingtomorrowsforests.co.uk/blogs/news/technical-note-how-do-trees-store-carbon.
12. Buis, A. (2019). Examining the Viability of Planting Trees to Help Mitigate Climate Change – Climate Change: Vital Signs of the Planet. [online] Climate Change: Vital Signs of the Planet. Available at: https://climate.nasa.gov/news/2927/examining-the-viability-of-planting-trees-to-help-mitigate-climate-change/.
13. NASA (2018). The Causes of Climate Change. [online] Climate Change: Vital Signs of the Planet. Available at: https://climate.nasa.gov/causes/.
14. IPCC (2018). Summary for Policymakers — Global Warming of 1.5 oC. [online] Ipcc.ch. Available at: https://www.ipcc.ch/sr15/chapter/spm/.
15. IPCC (2018). Summary for Policymakers — Global Warming of 1.5 oC. [online] Ipcc.ch. Available at: https://www.ipcc.ch/sr15/chapter/spm/.
16. 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.
17. Plant for the Planet. (n.d.). Why Trillion Trees. [online] Available at: https://a.plant-for-the-planet.org/trillion-trees [Accessed 13 Apr. 2021].
18. Planted, O.T. (n.d.). Reforestation Projects: The January 2021 Update. [online] One Tree Planted. Available at: https://onetreeplanted.org/blogs/stories/january-2021-reforestation-update [Accessed 21 Apr. 2021].
19. Great Green Wall. (n.d.). Great Green Wall — NEWS. [online] Available at: https://www.greatgreenwall.org/news#resources [Accessed 13 Apr. 2021].
20. Great Green Wall. (n.d.). Great Green Wall — NEWS. [online] Available at: https://www.greatgreenwall.org/news#resources [Accessed 13 Apr. 2021].
21. European Environment Agency. (2012). Trees help tackle climate change. [online] Available at: https://www.eea.europa.eu/articles/forests-health-and-climate-change/key-facts/trees-help-tackle-climate-change.
22. Houghton, R., Birdsey, R., Nassikas, A. and Mcglinchey, D. (n.d.). Forests and Land Use: Undervalued Assets for Global Climate Stabilization A BRIDGE TO A FOSSIL-FUEL FREE WORLD. [online] . Available at: https://www.woodwellclimate.org/wp-content/uploads/2015/06/PB_Forests_and_Land_Use.pdf.
23. Cosier, S. (2019). The world needs topsoil to grow 95% of its food – but it’s rapidly disappearing. [online] the Guardian. Available at: https://www.theguardian.com/us-news/2019/may/30/topsoil-farming-agriculture-food-toxic-america.
24. sdgresources.relx.com. (2020). World Soil Day 2020 | Sustainable Development Goals – Resource Centre. [online] Available at: https://sdgresources.relx.com/special-issues/world-soil-day-2020.
25. Sartori, M., Philippidis, G., Ferrari, E., Borrelli, P., Lugato, E., Montanarella, L. and Panagos, P. (2019). A linkage between the biophysical and the economic: Assessing the global market impacts of soil erosion. Land Use Policy, 86, pp.299–312.
26. Granite Seed and Erosion Control. (2019). How Do Trees Stop Erosion? | Granite Seed. [online] Available at: https://graniteseed.com/blog/how-do-trees-stop-erosion/.
27. Nowak, D.J., Hirabayashi, S., Bodine, A. and Greenfield, E. (2014). Tree and forest effects on air quality and human health in the United States. Environmental Pollution, [online] 193, pp.119–129. Available at: https://www.sciencedirect.com/science/article/pii/S0269749114002395.
28. Cool Earth. (2019). World Environment Day | Trees are living air-purifiers. [online] Available at: https://www.coolearth.org/2019/06/air-quality-trees/.
29. www.who.int. (n.d.). Air pollution. [online] Available at: https://www.who.int/news-room/air-pollution.
30. www.countrysideinfo.co.uk. (n.d.). The value of different tree species for insects and lichens. [online] Available at: http://www.countrysideinfo.co.uk/woodland_manage/tree_value.htm.
31. The University of Edinburgh. (n.d.). Forest loss escalates biodiversity change. [online] Available at: https://www.ed.ac.uk/news/2020/forest-loss-escalates-biodiversity-change. [Accessed 13 Apr. 2021].
32. theecologist.org. (2019). Planting trees to tackle flooding. [online] Available at: https://theecologist.org/2019/mar/14/planting-trees-tackle-flooding.
33. Trust, W. (n.d.). Can trees and woods help reduce flooding? [online] Woodland Trust. Available at: https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/british-trees/flooding/.
34. National Geographic Society (2015). Save the Plankton, Breathe Freely. [online] National Geographic Society. Available at: https://www.nationalgeographic.org/activity/save-the-plankton-breathe-freely/.
35. 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/.
36. www.usda.gov. (2019). The Power of One Tree – The Very Air We Breathe. [online] Available at: https://www.usda.gov/media/blog/2015/03/17/power-one-tree-very-air-we-breathe.
37. Buis, A. (2019). Examining the Viability of Planting Trees to Help Mitigate Climate Change – Climate Change: Vital Signs of the Planet. [online] Climate Change: Vital Signs of the Planet. Available at: https://climate.nasa.gov/news/2927/examining-the-viability-of-planting-trees-to-help-mitigate-climate-change/.