Tens of thousands of trees across South Lanarkshire will have to be felled over the next two decades due to the impact of ash dieback disease.
Between half and three quarters of all ash trees on land owned and managed by the council are estimated to need to be cut down due to the effects of the incurable and rapid-spreading fungus, described as “a huge threat to our environment” and “the most significant disease to affect broadleaved trees in the UK since Dutch Elm gained prominence in the 1960s”.
Arborists are working to monitor and take action on affected trees across the authority area, as well as preparing a landscape recovery plan covering the period to 2054 – with the programme of management and safety work estimated to cost between £5.1 million and £9.6 million.
Councillors on the community and enterprise resources committee were updated on the issue through a report outlining the condition of the estimated total of nearly 146,000 ash trees which are located either on council-managed land or “in private ownership within falling distance of the road [or] public area”.
Trees have been categorised into four groups according to health, with nearly 27,000 being rated in the poorest condition category of having less than 25 per cent canopy cover remaining, and a further 20,000 having less than half of their healthy foliage – meaning that already “viability is questioned” for nearly a third of all of the area’s ash trees.
Members were told that: “Ash dieback disease (ADD) has spread rapidly in South Lanarkshire [since it] was first recorded in 2012; European data continues to suggest it will lead to decline and death of 50 to 75 per cent of ash trees in Scotland over two decades and has the potential to infect more than 75 million ash trees across the country.”
Committee chair Councillor Robert Brown said: “The loss of ash trees through this pervasive disease has the clear potential to lead to long-lasting changes in our landscape, tree populations, canopy cover and the loss of ecosystem services, and may increase effects such as flooding and cause a reduction in carbon lockup.
“A significant number of ash trees grow alongside roads and will need to be removed before they reach the stage of being a hazard; as a council we have a duty to take reasonable care to ensure that falling branches or trees do not pose a danger to our residents.
“We have developed an ash dieback disease action plan to help us to tackle this issue head on. A key element is replacing the lost ash trees with appropriate native tree species which will protect and enhance the landscape and ecosystem.”
South Lanarkshire Council has told residents: “A significant number of ash trees across the area will have to be removed over the next 20 years. Where possible and where conditions allow, new trees will be replanted.”
A dedicated ADD page on the council’s website explains how the disease is spread by fungal spores which are carried by the wind, attach to ash leaves and spread through the tree, saying: “The fungus blocks the water transport systems of the tree causing leaf loss, lesions in the wood and on the bark.
“The crown of the tree suffers from gradual dieback and the branches become brittle and prone to breaking. Dead and diseased ash trees can pose real risks to human safety. Roads officers regularly inspect the public network to ensure there is no risk to users from overhanging trees.”
It adds: “Ash is an important species [and] not all ash trees will need to be felled. Some will be tolerant to ADD and it is important that these are retained; trees affected can provide valuable habitats for fungi, invertebrates, birds and small mammals and where it is safe to do so, consideration should be given to retaining declining trees for as long as possible.”
Funding of £500,000 was allocated last year and a further £200,000 in 2024-2025 for work on trees posing an unacceptable level of risk in areas including core roads, emergency access routes and busy parks and footpaths; and has been used to buy specialist equipment and employ temporary staff and contractors.
Councillors were told: “Estimates for worst-case tree works suggest that the council’s potential financial costs associated with dealing with 50 to 75 per cent ash dieback disease ADD mortality on land it manages or owns [is] between £5.1m and £9.6m – this excludes traffic management costs and replacement planting.
“Additionally, there are significant numbers of ash trees not owned by the council within falling distance of the road that could incur additional costs for the council to remove if deemed dangerous and not removed by the owner.
“There is no external funding from the Scottish Government to assist [councils] manage or mitigate ADD, despite this now being registered as a high risk for all local authorities; however, the scale of the problem is such that councils will not be able to manage ADD safely and effectively without additional financial support.”
South Lanarkshire’s action plan “prepares for a positive recovery phase to achieve a net biodiversity gain by 2034 and landscape recovery by 2054”, and officials say their approach “will also help retain more ash trees for longer so that we can reduce the impact of ADD and manage time and costs”.
The statistics for committee members and in South Lanarkshire’s action plan show that 40 per cent of the area’s ash trees are currently in the highest condition category of having canopy cover of more than 75 per cent – but that this figure has reduced by seven per cent since 2022.
More than a third of those in the bottom two condition categories are on private land, and the report notes: “The precise speed of decline of any individual ash tree is impossible to predict and will be influenced by several factors; long-term monitoring [of] health and focusing on those trees with severe symptoms, including root and stem decay, in higher-risk locations will require continued funding.”
Around 23,700 trees have been planted across the authority area in the past two years through projects including an ADD recovery scheme using £100,000 in climate emergency funding plus the ongoing development of the Clyde climate forest, with all planting projects gaining “notable community support”.
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