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Tree Risk & Responsibility

Every time we get battered by a gale or storm force wind in the United Kingdom, it is safe to assume that limbs and branches may be shed and that some trees may fall over.

Given the fact that we have approximately 900 million trees, together with 400,000km of highways and a population of 62 million, it is certain that many of these branches and trees could fall onto roads and endanger people or property. 

Over the last few years we have regularly witnessed tragic accidents caused by falling trees, which immediately create headlines and make it onto television news. On average, around six people in the United Kingdom are killed by falling trees and limbs every year. 

However, putting this into context equates to a risk of approximately one in five million which is extremely low. Unfortunately, the low level of risk may not be perceived in this way by the general public, particularly following an accident.

The Health & Safety Executive (HSE) have stated that the average risk of trees is firmly in the 'broadly acceptable' region of the tolerability of risks triangle, published in the HSE's 'Reducing Risks, Protecting People'.

The HSE believe that public safety can be considered as part of their overall approach to tree management, which sensibly ensures the maintenance of a healthy tree stock, retention of heritage trees and sound management of the environment. 

In their opinion, an effective system is likely to contain the following elements:

  • An overall assessment of risks from trees, particularly identifying groups of trees by their position and degree of public access;

  • Where there is public access, a system of periodic, proactive checks by a competent person linked with simple record taking;

  • Obtaining specialist assistance/remedial action when a check reveals defects outside the knowledge/experience of the surveyor; and

  • A system to report damage to trees, and to trigger checks after certain activities, i.e. severe gales.

Once a tree has been identified as a specific risk, action should be planned and taken to manage or correct the risk.

Within the arboricultural industry there are many differing opinions as to exactly how the management of tree risk should be undertaken, ranging from the traditional 'defect' led approach where every possibility of risk was removed, through to a more pragmatic approach where intervention should be kept to an acceptable minimum. This latter view is one which fits with modern balance between sustainability, environment and cost effectiveness.

One thing is sure, if the United Kingdom is to retain its wooded lanes and leafy suburbs, then we must be aware that being in close proximity to trees is not without risk. However, we must be pragmatic and accept that the benefits of trees - shading, carbon sequestration, increased property values, habitats, psychological benefits etc. - simply outweigh the risk.

However, tree owners need to be aware of the law and how it applies to tree and woodland ownership. Common law imposes on everyone a duty (known to lawyers as 'duty of care') not to injure his or her neighbour (Donoghue v. Stevenson). In practice it is likely to be an action of negligence, where there has been an omission to take sufficient care of the tree, where it leads to foreseeable harm. 

The owner of a tree may be liable in negligence if: 

  • The tree falls/sheds a branch;

  • Injury or harm is caused as a result;

  • The injury or harm was foreseeable;

  • The person who was injured is someone to whom the tree owner had a duty of care; or

  • Injury or harm was caused as a breach of that duty. 

This is further reinforced by the Occupiers Liability Act 1957 and 1984. 

Case law (Poll v Viscount Asquith of Morley 2006) should be noted with interest. This case involved a motorcyclist colliding with a fallen tree. The motorcyclist made a claim against the tree owners (defendants) for damages. Judgement was awarded in favour of the claimant. 

The tree was multi-stemmed and had a fungal bracket in an obscured position growing below the fork. The tree had been inspected by a forestry worker undertaking a 'drive-past' inspection and the fungal bracket went unobserved. The judge ruled that the inspection regime in place was insufficient to detect this type of structural weakness and that a different, more detailed, method of inspection would have detected the warning signs. Both expert witnesses in the case agreed that a prudent landowner with responsibility for trees adjacent to a public highway should have employed a 'level two' tree surveyor/inspector - someone who had sufficient training and expertise to identify, manage and assess trees for hazards. 

What this judgement serves to show is the heightened need for competence in undertaking tree hazard inspections. Within the United Kingdom there are a plethora of forestry and arboricultural qualifications, ranging from levels one to seven (National Qualification Framework). Recently, Lantra Awards and the Arboricultural Association launched two new qualifications in inspecting trees, aiming to create a standard that could be adopted throughout the industry. These include a three day course in Professional Tree Inspection (estimated NQF level 3) and an integrated assessment at the end of the course.

So, where does this leave the tree owner?

What we must not do is stop enjoying trees and treating them as a potential liability.

What we must do is enjoy our trees, manage them correctly by removing and pruning those that become dangerous and planting new ones on a sequential basis.

Risk should be quantified, based upon location and potential 'targets', i.e. what a tree might hit if it falls.

Work should be kept to an acceptable minimum, and need not become a financial burden.

Here are some of the common symptoms of tree defects:

  • Sparse foliage, unusual colour, small leaves. Foliage is often the very first part of a tree to show symptoms of stress, and is a good tool in assessing a trees condition. The Forestry Commission assess forest health from aerial photography and colour analysis.

  • Canopy die-back, dead branches. An obvious symptom, particularly in summer. However, be aware that some species (particularly Oak) naturally 'retrench' to a smaller canopy size with age.

  • Cracks, Splits, Bulges and Unusual Swelling. A possible sign of bio-mechanical tree defects. These are often not particularly significant, although in some cases leave the tree liable to limb shedding or failure

  • Fungal Fruiting Bodies, Decay. Most fungi are best observed in Autumn, and can range from around the rooting area to the upper canopy. Decay can be monitored over time and often does not mean that the tree must be felled or pruned immediately.

  • Rootplate Movement/Leaning Tree. Sudden movement of the rootplate can be a significant issue, particularly after high winds. Leaning trees that have always leant, should have adapted their growth to compensate. Sometimes, partial rootplate failure can be compensated for by limited canopy pruning.

If you would like advice on tree risk, please do contact our Principal Arboriculturalist, Brian Higginson (brian@crestwoodenvironmental.co.uk).