Thursday 4 February 2021

With around 8 million ash trees growing in UK towns and along highways, an aggressive tree disease epidemic could potentially drive a substantial increase in third-party personal injury and property damage claims against councils and highway authorities. 

In a recent article by Nick Atkinson, Research Fellow, Centre for Ecology & Hydrology, it is estimated that ash dieback (ADB) will kill 95% of ash trees in the UK over the next ten years, at a cost to the economy of £15 billion. 

According to The Tree Council, there are around 185 million ash trees across the UK and 3.6 – 4 million populate our towns and cities. Highways England estimates that over 4 million are growing next to their road network. 

Councils, highway authorities, housing associations and landowners need to be aware of the increased risk from tree branch failure, or entire trees falling. Subsequent damage or injuries can result in liability.

It is very likely that third-party personal injury and property damage claims, caused by infected and dying ash trees, will increase.

Landowners have a duty of care and must manage trees effectively where there is public access. Vegetation should be inspected regularly, and trees should be maintained so they remain healthy and safe.

Increased flood risk

First discovered in the UK in 2012, ADB is a fungus (hymenoscyphus fraxineus) that originated in Asia. There is evidence of the disease in most parts of the UK. The fungus penetrates the ash leaves, then grows inside the tree, eventually blocking its water transport system. Not all trees die from ADB, but once infected, the tree cannot be cured.

The common ash is the second most abundant large tree species in Britain.  Around 1,000 other species are associated with ash trees, including birds, insects, mosses, fungi and lichen. Forty-five of these are believed to exist exclusively on ash, so biodiversity and habitat loss is an issue. The decay and death of so many ash trees has wide implications: loss of carbon dioxide sequestration; less carbon dioxide absorbed from the atmosphere; and increased flood risk.


The UK Government has invested over £6 million in research to protect the ash from pest and disease threats. Generally, government advice is that uninfected ash trees should not be felled unless there are other overriding management requirements. Good progress has been made in screening for ADB tolerant trees, and the Government has developed management approaches and toolkits to provide guidelines for councils and public authorities with trees and woodlands under their control.

It is estimated that of the 185 million ash trees in the UK, 150 million are mature, and can reach 35 metres in height. Managing the escalating impact of ADB on these scales is a huge challenge.

High winds and storms can put even the healthiest of trees under stress. Any tree compromised by disease is highly vulnerable and, even in calm weather, has the potential to cause injury, damage or even loss of life.  

For example, a man was killed when a mature oak crashed over 20 feet down an embankment, and onto a houseboat below. A tree fell on top of a Fiat 500 travelling along a Suffolk road, and a parked Rolls Royce was flattened by a stricken tree in Hove.

Tree claims specialists

Sedgwick has a dedicated team of tree claims specialists, acting for major insurers, as well as large public sector clients, resolving third-party claims and advising on maintenance regimes.

If there is any doubt on what action to take on a tree that may be infected with ADB, or any other disease, it’s advisable to call in the experts.  The Arboricultural Association maintains an online directory of qualified and vetted tree surgeons and arborist consultants.

Sarah Harkin (sarah.harkin@uk.sedgwick.com) is Lead Specialist Adjuster at Sedgwick International UK. Sarah has over 14 years’ experience in dealing with tree root liability claims and heads up Sedgwick’s team of tree-related claims experts. 

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