Urban tree risk management

Arboricultural expert Chris Allder of ADAS, the UK's largest provider of rural and environmental solutions and policy advice, explains why the adoption of a tree risk management policy will prevent the loss of mature and increasingly rare trees from towns and cities.

Trees are vitally important to the landscapes of our towns and cities. Mature specimens of large species such as oak, ash, lime, sycamore, horse chestnut and London plane not only have a visual impact, they also bring value as a natural habitat. Furthermore, if climate change prediction models are to be believed, larger trees will have a significant role to play in the future, providing shade during hotter, drier summers.

However, recent evidence points to the fact that large trees are becoming increasingly rare as they are being replaced in favour of smaller, short-lived species such as cherries, rowans, whitebeams, birch and ornamental hawthorns. The reason for this can be attributed to local authority concerns about the risks that more mature trees pose to the public.

Urban tree issues

It is extremely unusual for trees to fail but from time to time, they do, and on rare occasions, they can cause significant or even severe damage. The problems caused by urban trees range from falling branches, loss of light, subsidence, and cracking or lifting pavements to even, in a worst case scenario, death; such as in 1999, when three people were killed by a defective ash tree that fell on to a highway in Birmingham.

Although extremely rare, these cases attract huge public attention and as a result, local authorities could become more inclined to remove potentially dangerous trees and thus any associated risks. But this policy is not the sensible long-term approach to take and instead, councils need to adopt a comprehensive arboricultural policy to reduce hazards and at the same time, ensure that large trees are not lost from the urban landscape.

Clearly, some local authorities already have policies and strategies driving their tree management programmes but the majority have no clear policy for assessing risk and as a result are constantly 'fire fighting'. Rather than carrying out surveys of their highway trees, many councils are only reacting to problems. With no specific direction or foresight, problems occur when they could in fact be prevented.

Tree management

The Health and Safety Executive recommends that local authorities have an effective tree management system and the Trunk Road Maintenance Manual - the Highways Authority guide - advises a maximum five year inspection cycle for trees. Planning ahead is the key to successful tree risk management and there are major benefits of adopting this approach.

For instance, councils will be held accountable for damage caused by trees through negligence and can be fined huge sums of money if prosecuted and found guilty. In addition, although early investment is required, in the long-term, a strategy will result in lower management costs and less reactive work required. The reduction of risks will also bring fewer complaints and will instil confidence from management, council members and, most importantly, the public.

In practice, local authorities can attain all these benefits through the adoption of a Tree Risk Management Strategy and the implementation of a Tree Risk Management Plan. The strategy should set out all the aims, objectives and principles that the local authority wants to achieve and the plan should include assessment of the entire tree stock. This will be prioritised, based on the location of each tree.

For example, a tree in a regularly frequented area will be deemed high risk. The use of geographical information systems (GIS) is also useful at this stage, to map the risk zones. Following this, scheduled inspection should take place and IT used to record data and produce an audit trail, identifying where actions are necessary and ensuring that they are undertaken. Every stage needs reviewing and monitoring so a risk management group should be set up to advise on the administration of the system.

Support systems

To ensure the success of the strategy and plan, endorsement is needed from senior management and council members. It is their support which will enable any policy to work effectively. If a tree officer is employed, they will need help and direction from the top-down. It is also important to note that an arboricultural policy such as this will require a certain degree of initial investment up-front.

With a strategy and plan in place, it is vital that the work doesn't end there. The plan will need to be constantly reviewed and updated, with assessment conducted on an ongoing basis.

There are currently some local authorities which are breaking new ground in having a strategy-led system which is defendable, addresses the duty of care and the tests of 'reasonableness' which is how courts assess the validity of negligence claims.

One good example of such a system is Southampton City Council's 'STORMS' - Southampton Tree Operational Risk Management System. In addition, ADAS has also worked with Nottingham City Council to produce a ring road tree health survey. Pioneering councils such as these are leading the way in arboricultural policy.

There are clear benefits to retaining large, mature trees in urban locations and any concerns about risks should not be blown out of proportion, with a resultant policy of cutting down older trees adopted.

Local authorities should not simply react to arboricultural problems and instead should pursue a proactive solution through the development of a tree risk management strategy and plan. Through doing this, councils can ensure that older, larger specimens of tree can remain an integral part of our towns and cities, without posing unacceptable levels of risk to the public or property.

ADAS is currently delivering the national Trees in Towns Survey on behalf of the Office of the Deputy Prime Minister. To find out more about adopting a practical arboricultural policy, Chris Allder can be contacted on 01235 438900


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