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Celebrating Urban Trees

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I’ve written in the past about the surprising amount of urban wildlife in our towns and cities. But immersed in the hustle and bustle of urban life, it’s sometimes easy to forget that we are also connected to nature by a city’s trees. Now in its sixth year, the Urban Tree Festival aims to redress by highlighting the importance of trees in our towns and cities. It also aims to connect urban dwellers, of all backgrounds, to nature. More people than ever, after all, live in cities in the UK. Running from the 13th to the 21st of May this year, what better time to delve into the benefits trees bring to our towns and cities, whether lining our streets or in our parks and gardens.

Britain’s Shrinking Woods

To help explain the importance of urban trees, we first have to step back in time. Humans have been clearing woods in the UK since they first started farming approximately 6,000 years ago. This process of tree clearing then continued over subsequent millennia. So, deforestation here is nothing new. But while tropical rainforests have been front and centre of campaigns to halt deforestation in more recent times, woodland loss in the UK is often unnoticed or ignored. This is despite the fact that according to Global Forest Watch, the UK lost 507 thousand hectares between 2001 and 2021. That amounts to a 14% decrease in tree cover since the year 2000.

Bristol urban trees
Bristol’s many trees help make it one of the UK’s greener cities

Some of the biggest drivers of deforestation here are clearance for agriculture and infrastructure development, such as roads and railways. Urbanisation is also a major cause. As our towns and cities grow and spread outside their former boundaries, developers fell more trees. The latest statistics, dating from March 2022, show that only around 13% of the UK is now wooded.

london trees
Incredibly, London’s eight million plus trees make it technically a forest

All this means that those trees that still exist in our towns and cities provide a link, however tenuous, to a time when they or their forefathers might have been part of a woodland rather than isolated standard bearers. As such, they play a part, however small, in offsetting deforestation in the UK. And many of them are far from isolated. Some of our towns and cities contain a surprising number of trees. For example, London has over eight million trees. That is so many that it can actually be classed as forest according to the United Nations definition of what constitutes one. This doesn’t mean, of course, that our urban trees are safe from felling themselves. The recent removal of more than 100 trees in Plymouth by the local council in a clandestine, overnight operation sadly bears this out.

Natural Benefits of Urban Trees

As well as helping counteract the UK’s ongoing deforestation, urban trees have a host of other benefits. Trees are vital to our efforts in combating the climate crisis. By absorbing carbon dioxide from the atmosphere and locking it away, they act as carbon sinks, helping to reduce emissions. And the opposite is also true; cutting down trees releases carbon dioxide which of course contributes to climate change. Another benefit linked to climate change is trees’ ability to provide shade and keep our warming urban spaces cooler. Trees also absorb urban pollution. A tree’s leaf pores absorb toxic particles and gases, acting as filters. The gases then break down within the tree’s structure while particulates eventually wash off into soil rather than remaining airborne. In addition, photosynthesis releases oxygen, which also improves air quality.

beech leaves
Tree leaves help filter air pollution in our towns and cities

Flood prevention is another key benefit. Trees not only absorb water from the soil, but they reduce the amount of rain reaching the ground. They also slow the rate of any rain that does reach the ground by producing a slower, steadier drip. This in turn reduces the risk of flooding. Root systems also prevent runoff and erosion.

jay urban trees
Once only found in woodlands, urban trees now attract jays in many cities

Finally, without trees, our towns and cities would be much less biodiverse. Urban trees support an enormous range of urban wildlife where otherwise there might be little suitable habitat. Invertebrates from snails, woodlice and spiders to moths, earwigs and beetles all live in, on or feed on urban trees. These then support animals and birds higher up the food chain, including birds and bats. Other bird and mammal species, meanwhile, feed directly on trees’ fruit and flowers. Trees also provide a substrate for some of the more pollution-tolerant mosses and lichens. Like the trees they grow on, these then also help capture carbon from the atmosphere.

Lichen
Many urban trees support lichens and mosses

Other Benefits of Urban Trees

There are also a range of less measurable, but equally important, benefits to us specifically as humans. Alongside the physical health benefits of pollution filtering and oxygen production, trees undoubtedly improve our mental wellbeing by reducing stress levels and lowering blood pressure. Scientists are becoming increasingly aware of how important connecting to nature is for our mental health. The Mental Health Foundation even produced a report in 2021 highlighting how vital this connection is. The report recognised that ‘nature’ isn’t restricted to remote places but can include tree-lined streets and urban parks. The bottom line is that people who are more connected to nature are often happier. The key is to make sure it is accessible to all. Urban trees, and the other wildlife they attract, play a crucial role in enabling this access. Beautiful in their own right, trees can also become part of art installations, boosting creativity.

South Bank art urban trees
Trees can be part of art installations like this temporary one on London’s South Bank

Our urban trees can also be fascinating links to the past. The placement of trees in our urban spaces can help reveal the history of a town’s planning phases. For example, the Victorians were responsible for many of our street trees as they adopted the French tradition of tree-lined urban thoroughfares in the 1850s. Cities also sometimes preserve the village trees swallowed up by suburban spread. The species chosen for various phases of planting can also reveal how different trees went in and out of fashion. Those Victorian street trees were often London plane trees, for instance, as they were versatile and took up little root space.

Brandon Hill oak
This oak was planted in Bristol to mark Edward VII’s coronation in 1902

Many towns and cities also have their own historically important trees. Some were planted to commemorate a particular event, such as a coronation or royal visit. Others became famous later by association. This includes the so-called Hardy Tree in St Pancras Old Church, London, now sadly fallen. The ash tree was enclosed by rings of tombstones, moved there to make way for the new Midland Railway, a project overseen by a young Thomas Hardy.

Common Urban Trees

As mentioned above, fashions in tree planting, as in much else, come and go. While many urban trees in the past were chosen for their hardiness and ability to cope with pollution, future planting will also have to take into account our changing climate. Trees may need to be resilient to drier conditions as well as the increasing number of new diseases arriving via plant imports. Currently, though, many of our towns and cities reveal that Victorian legacy of tree planting.

London Plane tree
Our commonest urban tree, the London plane, has distinctive mottled bark

This means that one of our commonest urban trees is the aforementioned London plane. A hybrid between American sycamore and Oriental plane, where the two species came into contact and managed to crossbreed is a bit of a mystery. It almost certainly happened in the 17th century, though, as a result of explorers bringing back exotic flora to Europe from Asia and the Americas. London planes have distinctive, mottled bark that peels away in segments, creating an army camouflage effect. This peeling helps them deal with urban conditions by periodically cleansing them of their pollution-loaded outer bark. They have round, spiky fruits which hang down and sycamore-like leaves.

Horse chestnut
Horse chestnuts produce conkers with their distinctive spiky cases

Horse chestnuts and sycamores are also common street trees. Both probably arrived in the UK in the 16th century but have become fully naturalised here. In spring, horse chestnuts are particularly attractive with their tall, white, candle-like flowers. The two species produce easily recognisable fruits in the autumn. Horse chestnuts have beautiful, shiny conkers, enclosed in spiky cases, while sycamores have double-winged fruits that hang in clusters.

Sycamore seeds
Sycamore seeds have ‘propellers’ to help them disperse

Silver birches are another popular urban tree due to their attractive white, peeling bark. Like plane trees they are also able to cope with polluted environments. They are also fast-growing. Many of our urban parks and public gardens also contain one or both of our native oak species. English and sessile oaks are both hugely important for biodiversity as they are capable of supporting hundreds of other species. Lichens, mosses, invertebrates, birds and mammals all find food, shelter or breeding spaces in our oaks.

silver birch branch
Silver birch is a popular street tree due to its attractive white bark

Urban Trees and Us

Urban trees are also vital if we are to inspire others to protect nature. A 2021 study found that the UK is one of the most nature-depleted countries in the world. But if people aren’t able to see and experience nature, they are unlikely to care whether or not this loss continues. With more people than ever living in urban settings in the UK, this connection has to be possible in our towns and cities. Preserving wildlife solely in nature reserves or in remote places will not be enough either to inspire and engage our future conservationists or indeed halt biodiversity loss. And this is partly why urban trees are so important. By providing contact with the natural world on a day-to-day basis, both with themselves and the other species they attract and support, they surely help us fight the growing disconnect between humans and nature.

Further Reading

Find out more about this year’s Urban Tree Festival here. There are walks, talks, activities and webinars galore.

The appropriately named Paul Wood’s book on London is a wonderful exploration of the capital’s trees. Combining history, myth and natural history, Wood invites the reader on seven routes through the city to showcase some of its finest and most interesting trees. The book undoubtedly backs up the Forestry’s Commission’s verdict that the city is the world’s largest urban forest.

Helen Babbs’ Sylvan Cities likewise looks at the history, folklore and benefits of urban trees but in a wider UK context. The book is also a useful identification guide to the twenty species most likely found on our city streets.

Mother and daughter team Ros and Nell Bennett have produced a handy guide to identifying 52 of Britain’s trees. Including keys to the fruit, leaves and bark, the book is a great way to get to grips with the trees you might come across in our towns and cities.

2 thoughts on “Celebrating Urban Trees”

  1. Heading for an interview sixty years ago I visited Bristol for the first time. I instantly fell in love with the city, the major reason being it’s magnificent trees.

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