London Trees: Could They Be The City’s Green Aircon?
After a long hot summer I’ve been reflecting on what can be done to help keep us all cool in the city. In exploring this idea, I went down a fascinating rabbit hole online about trees and found some really positive and hopeful information I wanted to share.
We tend to think of air conditioning as something that keeps us cool inside our homes. Yet London has its own enormous, natural cooling system – millions of trees growing in our streets, parks, gardens and woodlands.
With hotter summers becoming part of our reality, could the humble tree be one of the simplest ways of making our city more comfortable to live in, lowering both the temperature and our climate anxiety?
Nervous system regulation
If you keep up with the news, you’ll know how full of panic and catastrophe it can feel. We are constantly being presented with things that are frightening, upsetting or completely outside our control, and it’s very easy for our nervous systems to respond as though we are personally under threat. Living in that state of high alert, anxiety or despair isn’t good for our health, our quality of life or our relationships.
I think it’s important to anchor ourselves in the reality of our own daily lives and surroundings, and to hold the balance of understanding that while there are terrible things happening in the world, there are also wonderful things happening too.
I find it really helpful to keep the Serenity Prayer in mind and pay attention to the things that are within my control. I like to think that if everyone makes small, meaningful changes in their own lives and communities, those actions can add up to something much bigger. Having a sense of agency matters for our mental health, particularly when the bigger picture feels overwhelming.
Trees support our mental health
One of the things I find so interesting about trees is that they give us something very tangible to connect with. We can’t individually control the global climate, but we can care for the tree outside our house, spend time in our local park, plant something in our garden or simply notice what is growing around us.
There is also something about being surrounded by trees and green space that can help us slow down and settle. Research into the health benefits of spending time in nature has found associations with reduced stress and improved mood, and you don’t have to travel to the countryside to experience it. A walk through your local park, sitting beneath a mature tree with a book, or simply taking a few moments to notice the trees around you can be a small but meaningful way of stepping out of the constant stream of information and back into the present moment.
What about our children?
I’m particularly aware that many young people experience very real anxiety about climate change and can feel despair about what their future might look like. If you have children or teenagers, encouraging them to take small, meaningful actions can be a useful way of helping them feel less powerless. That might be planting something, helping to water young street trees during a heatwave, getting involved in a local conservation project or simply spending time looking after a green space they care about. It doesn’t mean ignoring the bigger issues or pretending everything is fine; it’s about finding something constructive to do with some of that fear, frustration and anger.
There is something about the longevity of trees, sometimes living for hundreds of years, that is innately grounding. Caring for them is more than a symbolic gesture, it’s a real investment in our future security. Sometimes watering a tree is a lot more useful than trying to change the whole system!
How trees cool the environment
It turns out that like us, trees sweat to regulate their temperature, as they release water it evaporates which takes heat out of the atmosphere. When this happens at scale, due to convection, woodland not only cools itself, it draws in and cools hot air from the surrounding area which help cool beyond the park boundary.
Research suggests that parks around 3–5 hectares in size (roughly the area of 4–7 football pitches) are large enough to cool not only the park itself but also surrounding streets by up to 150–300 metres during hot weather.
Conversely, brick and concrete absorb and retain heat, slowly radiating it back out as the air temperature drops overnight meaning that the more built up an area is the hotter it is and the less it cools overnight. Pavements can literally get baking hot!
London is an urban forest
Talk of climate change can feel overwhelming and depressing but there is hope! The good news is that London already has great parks and is one of the world’s largest urban forests, containing an estimated 8.4 million trees in public and private spaces.
Each tree makes a difference to air quality, soil stability and temperature management. Around 20% of London's trees are found in private gardens, making homeowners some of the city's most important custodians of its urban forest. Taking care of our parks and gardens makes a huge difference.
So what can we do to both protect and improve our environment?
8 Ways you can enjoy and care for your local trees.
1. Spend time under trees – There is compelling research on how time with trees can soothe our nervous system. For example, you may have heard of the practise in Japan called forest-bathing where people switch off technology and engage all their senses in a woodland environment. It reduces stress and improves overall mental health.
2. Choose the greener route - Whenever you can, choose the tree-lined street rather than the shortest route. Streets with mature trees are often several degrees cooler on hot days, while also being quieter, cleaner and more restorative. That small change to your daily walk can benefit both your physical and mental wellbeing.
3. Protect the trees you already have - One of the most effective actions we can take is not only planting new trees, but looking after existing mature ones. A mature tree provides far more cooling than dozens of newly planted saplings. If you have a garden, think twice before removing a mature tree. If you are making landscaping changes, leave enough space around tree roots rather than paving over them, and if you're replacing a fence or driveway, consider leaving more ground room for planting.
4. Plant something - Not everyone has space for a tree, but every garden, courtyard or balcony has the potential to become a little greener. If you have room, consider planting a native tree that will provide shade, support wildlife and help cool the local environment for years to come. If space is limited, shrubs, climbers or even a small tree in a container can still make a difference. Allowing a corner of your garden to grow into a mini wildflower meadow, creates valuable habitat for pollinators and helps to keep the soil moist.
5. Help trees survive heatwaves -Young trees are particularly vulnerable during prolonged hot weather because their roots haven't yet reached deep water reserves. If you notice a newly planted street tree looking thirsty, taking a watering can on your evening walk can make a real difference. Many councils actively encourage residents to help water young trees during dry spells, and this simple act can help them survive long enough to become the mature trees our communities will depend on for shade and cooling.
6. Get involved locally - If you'd like to make an even bigger difference, consider volunteering with a local conservation group. In North London, organisations such as the Heath Hands, Friends of local parks, The Conservation Volunteers (TCV) and London National Park City regularly organise tree planting, habitat restoration and practical conservation days. It's a wonderful way to care for your local environment while meeting like-minded people.
7. Support organisations protecting trees - If volunteering isn't possible, donating to organisations working to protect and expand our urban forests is another meaningful way to help. The Woodland Trust, Trees for Cities, and London Wildlife Trust all play an important role in planting trees, restoring habitats and campaigning for greener neighbourhoods. I've been supporting the Woodland Trust for over 20 years and love the work they do.
8. Speak up for local trees - When mature trees are threatened by development or unnecessary removal, local voices really do matter. Responding to council consultations, supporting your local Friends of the Park group or simply asking for more street trees in your neighbourhood can help shape a greener future. Mature trees take decades to replace, making them one of our most valuable natural assets.
While none of us can solve climate issues alone, we can choose where we place our attention and energy. I hope this article has inspired you to look at the trees in your neighbourhood with fresh appreciation—and perhaps even give one a grateful hug next time you pass!
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