How Long Do These Trees Have?: A Guide to UK’s Endangered Trees

The UK is renowned for its beautiful green landscape, strewn with some three billion trees and a variety of native species. It's hard to believe that this landscape for which we've become so famous could alter completely in years to come, as many of these species succumb to pests and diseases, as a result of factors such as globalisation and climate change.

So which UK trees are currently under threat, and what's being done to save them?

Oak

The mighty oak is quintessentially British and one of the best-loved trees in the UK. Although the oak is one of the most common trees in this country and is protected from over-harvesting, its existence is under threat.

Attack from pests is a major concern for the survival of the oak. In particular, the non-native oak processionary moth has been found to damage the foliage of the oak tree and weaken it, so that it becomes vulnerable to other diseases. This moth can even cause health problems to humans.

Yet, it's not just this pesky moth that can cause destruction to our beloved oak tree. In fact, a bacterial infection known as Acute Oak Decline (AOD) is more of a concern. It can completely decimate a healthy oak tree within five years. Symptoms include stems with black weeping patches and lesions, as well as branch dieback.

In order to safeguard the future of the oak tree, the Government has invested over £1 million into research to halt the spread of pests and diseases. University scientists have established a project that monitors pests and diseases that affect the oak, mapping where affected trees are in the country. Through their research, they aim to find a cure for AOD, so that the oak can remain a stalwart feature of our countryside.

Alder

Native to Britain and Europe, the alder tree is often found in wet woodland or near riverbanks. Like the oak, the alder is under threat. A type of fungus, known as Phytophthora, is attacking UK alder trees, causing lesions on stems and rotting the roots. It was once thought that this fungus was harmless to alder trees, but a new hybrid strain has developed to which the alder is no longer resistant. Once an alder tree is infected, it can die very quickly.

The number of alder trees affected by this fungus has increased since the 1990s and it's now estimated that one in five alder trees are affected by the disease.

Further alder loss can be prevented by felling affected trees and planting new trees in areas where previous disease hasn't occurred. Alders should not be planted near riverbanks prone to flooding, as this increases the risk of disease spread. Anyone looking to buy alder trees should make sure they purchase them from a reputable nursery who can trace the provenance of the tree so that it doesn't come from imported or infected stock.

Alder trees

Horse Chestnut

Although the horse chestnut tree isn't native to Britain, it has been part of our landscape since the 16th century and can be widely found up and down the country. As numbers steadily decline, the unimaginable suggestion that playing a game of conkers could become a thing of the past becomes increasingly possible.

There are two threats that could wipe out the horse chestnut. The first is a leaf-mining moth, which causes the leaves to go brown and then eventually weakens the tree. The second threat comes from a bacterial infection, called bleeding canker, which causes the tree to perish. Only four horse chestnut trees in the UK were found to have bleeding canker in 2000. By 2007, half of the UK's horse chestnut trees displayed symptoms of the disease, showing just how rapidly this virulent pest has spread.

Researchers have extensively studied the bacteria that causes bleeding canker and are using molecular technology to find ways to understand it further, in the hope of reducing its spread. In some cases, horse chestnuts can recover from bleeding canker, so removing symptomatic trees isn't always the best policy.

horse chesnut tree

Larch

One tree of particular concern in the UK at the moment is the larch tree. In recent times, over half a million of these trees in the west of Britain had to be culled due to the devastating effects of ramorum disease.

Other diseases that undermine the health of the larch include larch canker, larch bark beetle and butt rot fungus.

Larch tree

Beech

Native to southern England, this large, deciduous tree can survive for hundreds of years, yet its future in the British landscape is starting to look uncertain. Beech trees are reducing in numbers due to the fungal disease, Phytophthora, which causes the roots of the trees to rot. Infestations of an insect called Cryptococcus fagisuga can also weaken beech trees and cause beech bark disease, by sucking the sap from the tree.

The Corsican pine, Scots pine, ash, birch and juniper trees are also under threat with significant numbers already lost.

beech tree

What is being done to Tackle British Tree Decline?

Despite the worrying statistics relating to Britain’s treescape, steps are being taken to prevent further catastrophic losses, reminiscent of the impact of Dutch Elm disease during the 1970s.

A tree champion has been appointed by the Government, tasked with overseeing the planting of 11 million new trees in the UK. Experts claim this should only require 4,400 hectares of additional land to carry out. Where tree planting does take place, scientists urge that more natural forests are created, avoiding planting single-species in a regimented fashion. The tree champion will also keep a beady eye on the number of trees that are felled.

In order to combat the threat of pests and diseases, scientists are also looking at creating genetically-modified trees that are resistant to these harmful pathogens.

Much still needs to be done to tackle the problem of international plant trade, but consumers can do their bit by buying trees from reputable nurseries and finding out where the trees they purchase have originated from.

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