Why Do We Need Trees?

Tom Haddon

Tom Haddon

Nov 23, 2020

Trees are the oldest living organisms on Earth, and have been changing and adapting Earth’s atmosphere for over 300 million years. There are approximately 3 trillion trees in the world [1], which provide a huge range of benefits for humans and animals alike. This article will explain why we need trees, not simply for survival, but also for how they help us in our day-to-day lives – without us realising!


One of the most important things trees do is give us oxygen. In fact a single leafy tree can produce as much oxygen in a single season as 10 people inhale in a year [2]. Not only do they produce oxygen, but they also absorb carbon dioxide, making forests some of the best carbon sinks in the world. Although different trees have different rates of absorption, estimates suggest that an average fully mature tree will absorb over 48 pounds (22kg) of carbon dioxide in the course of the year, whilst producing oxygen at the same time [3]. As well as this, trees can literally act as air filters to make the air we breathe cleaner. Particles and pollutants get trapped by the leaves and the bark, removing them from the air – this makes trees important not just in the forests and woodland, but also in the cities that we live in to clean the air. 

Fight climate change

As we know, trees absorb carbon dioxide naturally. And this is good news for us, because this means trees help to fight climate change. The less CO2 in the atmosphere means there will be less of a greenhouse effect, and so there will be less warming. For individuals, trees help keep us cool, by providing shade, but also through evapotranspiration – where water evaporates from  trees and hence cools the air around them. In hotter climates this can be more important than you think –  in the USA for example, neighbourhoods with well-shaded streets can be up to 6-10 degrees fahrenheit cooler [4], which has knock-on effects such as lower air-conditioning energy use. 

Our health

© Photo by Emma Simpson on Unsplash

At Earthly, we think being around nature feels amazing. And it doesn’t just feel good – it does good as well! There have been many studies showing that spending time outside around trees is beneficial for your health in a number of ways. In fact, contact with nature has been found to be so beneficial that it is even being prescribed by doctors…

For example, Leeds Beckett University have found that “prescribing contact with nature for people who have low mental health levels is excellent value for money by improving people’s wellbeing” [5]. Meanwhile Exeter University collated research from across the world stating that overall “medical research from around the world demonstrates that a Green Prescription can deliver physiological and psychological benefits for patients, even if the exact mechanisms by which these accrue are not yet fully understood” [6]. 

As well as being excellent for mental health, being around trees and nature facilitates naturally lower death rates and heart disease rates [7]. This may also be linked to a greater opportunity for exercise in outdoor natural areas [8]. 

Heading into winter, when people are more likely to spend longer and longer inside, especially with Covid-19 restrictions ramping up, spending some time outdoors amongst nature will have many health benefits. As well as playing a vital part in sustaining good mental health, they can also boost the immune system [9].

For more information on the health benefits of trees visit NHS Forest: https://nhsforest.org/evidence-benefits

For wildlife and habitats

Trees provide a natural habitat for hundreds of animals and birds in the UK alone, but also act as protection for these habitats. When trees are young and mature, they provide food and habitation to communities of birds, insects and fungi, and when they become ancient, species such as bats, owls and woodpeckers use the trunks to live in. One mature oak tree can provide a home for as many as 500 different species! [10]

Trees also protect against flooding, by dramatically reducing the amount of water entering watercourses. A single tree can absorb as much as 450 litres of water at one time [11]. The roots of trees also stabilise the ground, protecting against landslides or other similar impacts.

More trees please!

Trees are very important to all life on Earth. Although there are still 3 trillion trees on Earth, it is estimated that 15 billion trees are cut down each year, and the global number of trees has fallen by approximately 46% since the start of human civilisation [1]. We need to stop taking trees for granted and help care for them. After all, they’ve been caring for the planet and its inhabitants for millions of years. 


[1]  Crowther et al., (2015). Mapping tree density at a global scale. Nature, 525 (7568), pp.201-205.https://www.nature.com/articles/nature14967 

[2] Helmenstine (2019). How much oxygen does one tree produce? https://www.thoughtco.com/how-much-oxygen-does-one-tree-produce

[3] Stancil (2019). The Power of One Tree – The Very Air We Breathe.  https://www.usda.gov/media/blog/2015/03/17/power-one-tree-very-air-we-breathe

[4] The Arbour Day Foundation. (2020). How Trees Fight Climate Change in Your Community. https://www.arborday.org/trees/climatechange/fightCommunity.cfm

[5] Leeds Beckett University. (2019). Improving Mental Health at Nature Reserves is Excellent Value for Money. https://www.leedsbeckett.ac.uk/news/1019-improving-mental-health-at-nature-reserves-is-excellent-value-for-money/

[6] University of Exeter. (2014). A Dose of Nature Addressing chronic health conditions by using the environment  https://nhsforest.org/sites/default/files/Dose_of_Nature_evidence_report_0.pdf

[7] Mitchell R, Popham F., (2008). Effect of exposure to natural environment on health inequalities: an observational population study. Lancet. 372: 1655-1660 https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(08)61689-X/fulltext  

[8] NHS Forest (2020). Evidence of Benefits. https://nhsforest.org/evidence-benefits 

[9] Lem. (2013). Green time: just what the doctor ordered. https://www.evergreen.ca/blog/entry/green-time-just-what-the-doctor-ordered/   

[10] Royal Parks. (2020). Why are trees so important? https://www.royalparks.org.uk/parks/the-regents-park/things-to-see-and-do/gardens-and-landscapes/tree-map/why-trees-are-important 

[11] Trees for Cities (2020). Trees in our Cities: 10 Reasons We Need to Plant More. https://www.treesforcities.org/stories/trees-in-our-cities-10-reasons-we-need-to-plant-more





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