Tree inspection process

4. Hazard and risk

Hazard

Hazard is the potential to cause harm.

Like all living organisms, trees are subject to decline, senescence (senescence is the natural aging and breakdown of a tree, while decline is often premature aging/breakdown caused by abiotic and biotic factors, such as pests and diseases and environmental stress) and collapse.

They can also be damaged physically or invaded by pathogenic organisms. As trees deteriorate so they are increasingly likely to shed branches or fall in severe weather and their potential to cause harm increases.

The borough has an important collection of exotic (non-native trees) and native (species which existed prior to, or established at the end of, the last ice age (10,000/11,000yrs ago). Naturalised natives are defined as trees that established after the Channel was formed or introduced at a later period but have climatised to the UK) trees many of which are in decline but still retain high amenity value and are uniquely valuable to wildlife, whatever the physical condition of the tree. Remedial action is only necessary when there is clearly a significant risk to life or property. This might mean removing part of the tree or reducing the level of public access in the vicinity.

Risk

Risk is the level of likelihood that a hazardous tree will cause damage.

Risk is primarily related to the location of the tree. It reflects the intensity of use of the immediate surroundings of the tree and the proximity of the tree to buildings or other structures.

The intensity of use by staff or visitors to our greenspaces is not evenly distributed.

Some areas are naturally inaccessible, due to dense woodland or undergrowth, while other areas are heavily used throughout the day. The levels of risk, therefore, vary across our sites and this has been recognised in this document through a system of zoning (high, medium and low risk), with each zone given a frequency of inspections.