As temperatures continue to rise, heatwaves are becoming an increasingly familiar part of life across the UK. Recent summers have seen record-breaking temperatures, and experts expect extreme heat events to become more frequent and intense as the climate changes. For towns and cities, this presents a particular challenge.
Urban areas are especially vulnerable to overheating because of what scientists call the “urban heat island effect”. Roads, pavements and buildings absorb heat from the sun during the day and slowly release it at night. This means cities can be significantly warmer than surrounding rural areas, particularly during heatwaves. In Sussex, where much of the population lives in coastal towns and developed urban areas, rising temperatures pose growing risks to health, wellbeing and local wildlife.
Fortunately, trees offer one of the most effective natural solutions.
Nature’s air conditioners
Trees cool urban environments in two important ways. First, their canopies provide shade, reducing the amount of solar energy absorbed by buildings, roads and footpaths. Second, trees release water vapour through a process known as evapotranspiration. As this water evaporates from leaves, it cools the surrounding air in much the same way that perspiration cools our skin.
Research across 293 European cities found that urban trees can reduce surface temperatures by between 8 and 12°C compared with heavily built-up areas during summer conditions. The same study found that tree cover was two to four times more effective at cooling cities than treeless green spaces alone. Meanwhile, a review of more than 100 studies concluded that trees consistently outperform other forms of urban vegetation when it comes to reducing extreme heat.
This isn’t just a theory. Cities around the world are investing heavily in urban tree planting to protect residents from rising temperatures. In Medellín, Colombia, an ambitious programme of green corridors helped reduce temperatures in some of the city’s hottest areas by up to 2°C while also improving biodiversity and air quality.
What can we do?
The good news is that local action can make a real difference here in Sussex too.
Planting new trees is important, but caring for existing young trees is just as critical. Thousands of trees are planted across the UK every year, yet many fail to survive their first few summers because they do not receive enough water. During dry spells, a few buckets of water each week can dramatically improve a young tree’s chances of survival.
Residents can also support community planting projects, create space for trees in gardens, advocate for more ambitious tree planting policies, and encourage local councils and developers to protect and expand urban canopy cover.
Finally, local voices matter. By encouraging councils, developers and public bodies to prioritise tree planting and protection, communities can help shape cooler, greener and more resilient neighbourhoods.
At Tree Action, we believe that everyone has a role to play in creating cooler, greener and more resilient communities. Whether you volunteer at one of our community tree care sessions, help water young trees during dry weather, support our work through a donation, or simply encourage others to get involved, you can make a tangible difference.
Want to get involved?
Join one of our community events, support our work with a donation, or become a volunteer tree champion in your local area.