Whilst trees have many values - social, environmental and economic - they may, if suffering from certain mechanical defects, represent a hazard in areas where people and property are present. It is therefore important for managers to be aware of tree-related hazards.
Although trees may be planted for one principal purpose, there are usually other respects in which they have value, whether positive or negative. The management of trees should therefore embrace several objectives which, for example, may relate to timber production, amenity, wildlife conservation and the control of hazards.
In the case of hazard management, it is necessary to take reasonable steps to identify trees which represent a significant risk to people or property and to deal with them accordingly. This should, however, be done in a way which minimises the loss of value for people and wildlife.
To this end, a number of objectives relevant to hazard management can be listed as follows:
- to control risks to people who work with trees or who may be close to them;
- to avoid the unnecessary removal or disfigurement of amenity trees or of trees with high wildlife value;
- to conserve habitats that are provided by trees, including those that are old and decaying.
Where a tree is hazardous because of decay or structural weakness and shows external signs of being in such a condition, the occupier of the land on which it stands is normally liable under UK laws for any personal injury or other damage it causes by breaking or falling. This liability arises from provisions by which the occupier has a common duty of care to others who enter the land or its vicinity. The occupier is defined as the person 'occupying or having control of the premises', and this effectively means whoever has possession of and controls the land. For example, the Forestry Commission is, in law, the occupier of the forest it manages, although there may be certain circumstances where a forestry contractor who is in control of a particular area could be considered to be the 'occupier'.
No tree is entirely safe, given the possibility that an exceptionally strong wind could damage or uproot even a mechanically 'perfect' specimen. It is therefore usually accepted that hazards are only recognisable from distinct defects or from other failure-prone characteristics of the tree or of the site.
Deciding which trees to inspect
The need for a particular tree or group of trees to be inspected depends on the usage of the area within their potential falling distance. Inspection is unquestionably necessary within zones where people, or high-value items of property, are continuously or frequently present close to trees which are capable of being hazardous. Clearly, however, there are remote areas where tree failures are very unlikely to cause injury or damage, even though the risk of such an outcome cannot be entirely disregarded. Even at a more heavily used site, it could be that the risk is currently very low by virtue of the size and species of the trees present. There cannot, therefore, be a hard and fast distinction between sites where inspection is essential and where it is entirely unnecessary. Occupiers must decide what is reasonable, because the Courts expect them to take 'reasonable steps' to inspect their trees and to remove or reduce hazards to people and property. Specialist advice can be sought on the zoning of areas where inspections should be made.
The key consideration is foreseeability; if it can be reasonably foreseen that anyone (guest or trespasser) could be at risk, the occupier has a duty of care to reduce that risk within reason.
Level of inspection
It is sufficient initially to look for external signs that may indicate that a hazard exists. If no significant hazard is revealed, further action is not generally required until the next inspection. If evidence of a hazard is found, more detailed investigation by a specialist would be advisable where:
- the full extent of the suspected hazard is not clear from external examination;
- the tree is of high value (e.g. for amenity or wildlife) and there is reason to believe that it cannot be made safe without significantly lessening its value.
A Basic Tree Survey and Inspection course from Grounds Training aims to provide specific tree survey and inspection training at a basic level for contractors, highway engineers, tree wardens, grounds maintenance staff, rangers and other persons of a non-arboricultural background or with limited arboricultural knowledge, to allow them to identify obvious defects from ground level and then to report their finding to a line manager.
The next course will be held at Abbey Gate College on Tuesday 3rd April. Book your place now by calling 01902 440251 or click here to fill in the booking form.
The original article 'Hazards from Trees' is available from the Forestry Commission here.