Conserving our tree heritage in a time of climate crisis

Left: The classical arch at Hampstead Heath (Photo: The Woodland Trust) Right: Ancient pollarded hornbeam trees, Hatfield Forest (Photo: Tom Reed)

The historic environment is composed of buildings and their surroundings. This may include both the hard and soft townscape or landscape features of their surroundings, their gardens and, in urban settings, the spaces between buildings. Trees are a vital element of these spaces, just as they are in gardens, parks and natural landscapes. And often these trees are of historic interest in their own right, whether as part of a designed landscape setting that is of a particular age and importance, or because the trees themselves are of great age.

It is particularly pertinent to highlight the importance of the role of trees in reducing heat in urban areas, in providing nesting sites and food sources for wildlife, in cleaning the air and absorbing carbon. In particular, ancient and veteran trees are internationally important heritage assets in their own right, as well as being living carbon sinks.

This article will explore the idea that these ancient and veteran trees are an overlooked heritage asset in need of greater recognition and conservation. It will also look at wider protection and conservation of trees, both for their heritage value and as part of efforts to tackle climate change.

An ancient tree is one that has passed beyond maturity and is old in comparison with other trees of the same species. It will probably have a very wide trunk relative to other trees of the same species and it is very likely that it will be hollow. Its canopy may be small. The UK’s oldest tree is the Fortingall Yew in Perthshire, estimated to be 2–3,000 years old.

The term veteran may be applied to ancient trees and to mature trees that have developed some of the features found on ancient trees such as exposed dead wood, fungi, and hollowing and decay within their trunks, branches and roots. As a result, old and veteran trees both provide cavities and crevices which are important for wildlife.

The UK has an usually high number of old trees compared to other European countries. There are 115 recorded oak trees with a girth (circumference) of more than 9m in England, and only 96 in the rest of Europe combined. The UK also has more ancient yew trees than any other European country – 978 in England compared to 77 in France and just four in Germany. A number of these trees are likely to be more than a thousand years old.

Among the reasons for this remarkable tree heritage are a long tradition of private landownership, the near lack of destructive modern wars and successive forms of early landscape conservation, for example for hunting (medieval deer parks) or recreation and romanticism (parkland). Nowadays ancient trees are found scattered across the landscape – in road verges, parks and gardens, as well as within the boundaries of historic landscapes like medieval deer parks and wood pastures. Most recorded ancient trees are not located within ancient woodland.

For 20 years the Woodland Trust has collected recordings of these trees in the Ancient Tree Inventory, with the support of a network of volunteers. This online map is available to everyone and currently has more than 100,000 trees listed, including around 20,000 verified ancient trees. Despite their irreplaceable value and scarcity, ancient trees are still under threat – from pests and disease, from inappropriate management, climate change, and sometimes from development.

Despite their age and immense value, ancient trees are still under threat. As I write this efforts are underway to save a 700-year old oak tree in a garden in Reading, Berkshire that dates back to the English Civil War. The tree is subject to a planning application to fell it to enable the construction of a house. There are just 300 recorded oak trees of this size in the country. The oak tree has a tree preservation order (TPO) and planning policy should ensure this tree is protected. But ultimately the decision on whether to fell the tree lies with the local council, and a TPO is superceded by planning permission if it is granted.

Old trees and woods have protection through national planning policy which has been strengthened in recent years. In England paragraph 180 of the National Planning Policy Framework says: ‘Development resulting in the loss or deterioration of irreplaceable habitats (such as ancient woodland and ancient or veteran trees) should be refused, unless there are wholly exceptional reasons and a suitable compensation strategy exists’. Recently the National Planning Framework in Scotland was updated with similar wording.

National planning policy gives a basic level of protection to trees affected by development but there is no automatic right of protection for the nation’s oldest and most special trees. In this respect trees differ from other nationally important heritage and ecology, falling between the cracks of our heritage protection and wildlife protection systems.

There is a notable example of this at Hampstead Heath in London. At the north end of the heath is a Grade II listed brick wall and archway (see photo) which was the former garden entrance to Pitt House, the convalescent home of William Pitt the Elder who was Prime Minister from 1766 to 1768. Next to the wall is a towering centuries old beech tree, potentially as old as the house itself (the house was demolished in 1952 and the brick wall and archway are all that remain). A few years ago the tree was undermining the stability of the arch, and the tree was at risk of being felled to preserve the grade-listed structure. Fortunately a solution was found which enabled the retention of both the wall and the tree through the use of adjustable props at the base of the tree. This is the ideal – active conservation of both our built and natural heritage.

There are cases where trees are protected, but this is often as a by-product of protecting something else. Tree preservation orders can be an effective emergency protection for trees of high ‘amenity’ value to the local community, but they are not designed as a strategic tool for the conservation of old and special trees. Trees within conservation areas are also subject to a higher level of protection reflecting their value in terms of urban landscape character. Similarly, trees in legally protected places like sites of special scientific interest will have protection through the site designation. Felling licenses also act as a control on the indiscriminate felling of trees although, in most cases, an individual tree is not likely to contain a sufficient volume of timber to require a consent for its felling.

A number of countries in Europe now have legal protection for old and special trees. In Italy a law protects more than 20,000 monumental trees, and Romania passed a similar law this year. A number of countries including Poland have laws that protect ‘natural monuments’ including many old trees. The Woodland Trust is exploring the potential for a similar system here to help protect and conserve our oldest trees.

The history of people is writ large in our oldest trees and woods. For example the woodlands around the fringes of London literally fuelled the expansion of the city, whether by making charcoal from oak and hornbeam to provide fuel for cookhouses and metal working or the timber taken to make countless buildings and great ships like Sir Francis Drake’s ship the Golden Hind which was made from oak timber from Great Stake Pit Coppice near Norwood.

Experts can read human history in the form and shape of trees. Think of pollarded trees which have been cut repeatedly at the top of the trunk, over centuries in some cases, to form their distinctive shapes (see photo 3). But to most people trees are an artefact of nature and, perhaps, easy to overlook given their relative ubiquity in our lives. This valuing of built heritage over natural heritage reflects long standing frameworks for valuing, and exploiting, the natural world.

Climate change and the shadow of a rapidly warming world provides urgent context for redressing this imbalance. The UK is a relatively tree-depleted country. We have 13 per cent forest cover compared to a European average of 38 per cent. The UK is a densely populated and deforested country that is in a long-term trend of reforesting, but current efforts need accelerating. Trees can help to create more resilient environment in rural and urban areas. On farms they can help to reduce soil erosion, control pollution and provide shade for livestock. In cities they can provide cooling and shade and help to reduce air pollution.

We urgently need to increase the number of trees we have. But alongside planting trees it is as important to effectively protect the trees we already have. It is in the mid to late stages of life that a tree typically stores the most carbon. Studies by Forest Research on the carbon storage levels in large urban trees demonstrated that the amount of carbon stored was low in the young and semi-mature trees, and highest in the over-mature and veteran trees. Carbon storage is proportional to tree volume so it should increase as trees gain in girth and height with increasing age. How can we reduce life-shortening threats to trees and ensure our old trees live to the end of their natural life? The Woodland Trust has developed guidance with the Ancient Tree Forum based on three guiding principles:

1. Give ancient and veteran trees as much space as possible, both above and below the ground by allowing the tree crown adequate spreading room and protecting the ground surrounding a tree to prevent root and soil damage.
2. Retain dead trees and decaying wood.
3. Identify veteran trees of the future and establish any new trees well away from existing veteran or ancient trees to avoid creating competition for light, water or nutrients

The conservation and protection of old trees can have multiple benefits for preserving heritage and the historic character of places. Looking after our trees, and finding the space to plant more, can be part of the active conservation of these places helping to make them more resilient. In so many places trees have become part of our history. We now need them to help create our future too.

This article originally appeared as ‘Living legends: Conserving our tree heritage in a time of climate crisis’ in the Institute of Historic Building Conservation’s (IHBC’s) Yearbook 2023. It was written by Adam Cormack, head of campaigning at The Woodland Trust. For more information on the Woodland Trust’s Living Legends campaign go to http://www.woodlandtrust.org.uk/livinglegends

--Institute of Historic Building Conservation

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