Why trees for cities?
Brighton & Hove City Council has announced today that is planning to plant over 70,000 young ash trees over the next couple of years. The hopes are these trees will be resistant to the ash dieback that has been sweeping the country since the early 2000s, a disease which has caused people to stop and reflect again on the benefits of trees. But how do these benefits translate to a city – or other urban setting where we may take trees for granted?
There are a surprising range of benefits from having trees in cities – in parks, our streets, urban green spaces, hospital grounds, housing estates, industrial estates. Despite the struggle to fund maintenance, maintain arboricultural skills, protect important trees, and plant new trees, studies generally confirm there is a net benefit for having urban trees, wherever we find them, or can plant them in the right places.
Wildlife
In terms of wildlife, trees provide homes for other species – birds, butterflies, bats for example – as well as a myriad of other invertebrates, plants and fungi. Ash trees in parks and urban woodland provide the right conditions for sensitive plants like dog violet to grow. Their seeds feed bullfinches, dead branches are home to lesser stag beetles, and they are favoured by a range of moths. Elm trees are associated with white-letter hairstreak butterflies. Oaks are host to 284 invertebrate species and 324 lichens, and are uniquely important for the caterpillars of purple hairstreak butterfly, oak lutestring, great oak beauty and the scarce merveille du jour moths. Other common urban trees like sycamore harbour a relatively low biodiversity, but a huge biomass of insects like aphids, which in turn provide food for a wide range of birds.
Nature connection
Urban trees give people a chance to be close to this wildlife – especially those who may not have the means to access rural green spaces, or have their own gardens. Research shows that taking time to notice nature when we are outside boosts life satisfaction and wellbeing, and can make it twice as likely that we take action in our daily lives which is good for the environment.
There are some surprising mental health benefits. Recent studies have shown that living within 100m of street trees is associated with a reduction in antidepressant prescriptions – particularly in areas of lower socioeconomic activity.
Climate emergency
There are a range of climate benefits – sequestering carbon is far from the only one. Trees can prevent up to 45% of rainfall reaching the ground, helping reduce the risk of urban flooding. Trees help cool urban environments – a good thing in reducing illness and deaths related to heat waves – and can also have the knock on benefit of reducing the energy required to cool or heat buildings nearby. The right trees in the right places can also improve urban air quality.
Aesthetics and performance
Given how attractive we find trees, it’s not surprising to learn that they tend to boost property prices and attract higher paying tenants. But tree-lined streets also encourage walking and cycling – both low carbon forms of transport. Walking under trees can help us feel full of ‘awe’ – an emotion that leads us to be kinder, more sociable, more neighbourly and even more generous. Views of trees from the window have also been shown to improve children’s grades, reduce stress and promote recovery for hospital patients, help restore attention of office workers, and boost creative thinking.
Culture
And last but not least, trees are part of our urban cultural heritage. Our towns and cities were often planned around significant trees or woods, our roads and neighbourhoods named after them, and most of us can think of a favourite tree we like to see from the bus window, sit under, or use to mark the changing seasons. We celebrate our trees, dress them, protect them, and campaign when they are under threat.
In Brighton, like most cities, we have place names inspired by trees. Mile Oak, Woodingdean, Wood Vale, Elm Grove, Laburnum Avenue. We have the national collection of over 17,000 elm trees, including the oldest and largest in Europe – the ‘Preston Twin’ (pictured) – and one of the oldest and oddest in the UK – the ‘Weeping Wych’ in Pavilion Gardens.
Threat of disease
Brighton is, like most cities, at risk of losing its ash trees, the third most common tree type in the UK. There are estimated to be over 170 million ash trees left in this country, and over 2 billion saplings and seedlings. Their total loss would be staggering. It would change our landscapes forever in an even bigger way than the loss of 25 million elm trees to Dutch Elm Disease did in the 1920s and 1960s.
There remains hope that disease resistant strains of ash and elm will emerge, and careful management can recover the situation. Today’s announcement from Brighton & Hove City Council is therefore very welcome and not before time.
There are a host of other pressures on urban trees. Inappropriate felling, lack of maintenance, poorly managed roadworks and a lack of replacement for example. One response, from organisations like Forest Research, has been to harness technology. The UK urban canopy map uses a free tool called i-Tree Canopy to create maps of urban trees. These can be used by planners and policy makers – even the public – to identify areas of deficiency, drive up ecosystem benefits, and decide how best to protect trees from future threats.
Here are some things you can do to help.
How you can help
- If you’re in Brighton, volunteer to plant the new ash trees. Dates are being advertised – just turn up, get some exercise, boost your mental health, and make some new friends. And don’t buy or move elm logs, timber or furniture in or out of the city.
- Plant a tree in your garden, your company estate, or your street. As the saying goes, the best time to plant a tree was 20 years ago. The second best time is today.
- Map your local neighbourhood for trees, using the free i-Tree Canopy tool.
If you can’t do those things then just go outside and make friends with a local tree.
Hug it, climb it, sit beneath it. Just don’t take it for granted.
Written in response to request for interview on BBC Sussex, 25 January 2023.