BEING called a 鈥渢ree hugger鈥� used to be a mild insult, but there is a growing appreciation for the benefits of trees. Their best-known environmental asset is to take in carbon dioxide from the air, but in towns and cities they have other useful qualities too.
In summer, trees cool hot streets, while in times of high rainfall, they take up water, stopping it from running into drains too quickly and causing floods. As climate change will lead most of the UK to have , trees help on both counts.
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Cities and towns are usually several degrees warmer than the surrounding countryside, mainly due to their high proportion of hard surfaces like pavements and asphalt, which absorb more heat from the sun. But streets with trees can be several degrees cooler than bare ones thanks to the shade the plants create and their ability to take up water, which evaporates from leaves, cooling the air.
carried out in Manchester in the UK suggests trees reduce radiant temperatures of hard surfaces in summer by 4掳C to 7掳C. On a large scale, that should cut deaths caused by heatwaves and the power used by air-conditioning units.
Some suggest tree-lined roads are linked with better mental health and less crime. While it is hard to show if trees are really the cause, as more affluent areas tend to have more street trees, most would agree that they make an area feel like a more pleasant place to be.
People with front gardens can do their bit to help by planting trees next to pavements where they add to street shade. When choosing a tree, 鈥渢hirsty鈥� varieties and ones with broader leaf canopies are best for cooling and soaking up water, although they do take more watering during dry spells, says Elisabeth Larsen at the UK鈥檚 Royal Horticultural Society.
Anyone without a garden can still help by joining campaigns to green urban spaces. While many local authorities let people request trees for their street, this is a poor way to allocate planting, says Jon Burke, a former councillor for the London borough of Hackney, who recently began a massive planting programme there. That is because better-off households are more likely to make requests, worsening inequalities in tree cover.
Instead of asking for a tree on their road, people should lobby councils to begin equitable urban greening programmes, says Burke. 鈥淪treet trees are a public necessity in a warming world.鈥�
There is another way to help. Local authorities may fail to water new saplings regularly and let them die. So people can join volunteer groups or just unofficially 鈥渁dopt鈥� new trees, whether in their own road or elsewhere, and regularly water them during dry weather.
If no one鈥檚 looking, you could even give them a hug.
What you need
A watering can
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