All arborists will invariably carry out tree surveys from time to time. They can be conducted on land owned by public sector bodies or on private estates. They ensure that the individual or organisation managing the land has the correct information that they need to make decisions regarding how they will manage the tree stock.

There is official guidance, namely British Standard BS5837, which sets out how decisions should be made when managing trees. A tree survey is needed before any decisions can be taken.

Information Revealed by a Tree Survey

A properly conducted tree survey will yield essential information about the trees in the location in question. Some of the most important information includes:

• The tree species, which is recorded in scientific nomenclature.
• The age of the tree.
• The physical dimensions of the tree including the trunk diameter at a recorded height and the overall height of the tree. This is identified using measuring instruments.
• The health and predicted life expectancy.
• Recommendations for managing the tree in the future, this could include restorative work or even removal.
• Compliance with any legislation that applies to the tree such as the Wildlife and Countryside Act 1981.
• Predicted impact of any proposed development on trees in the locality.
• Providing information for computer generated modelling.
• Pinpointing trees that add value to a development, those that are protected by law and those that do not enhance the landscape and can be safely removed.
• Identifying trees that present a hazard due to their physical condition.

Carrying out a Tree Survey

A tree survey is often a significant undertaking and may involve several arborists and specialist equipment. Before you start, it is essential to protect your own safety and that of your employees by identifying any hazardous trees. A preliminary scoping survey is carried out to identify ‘Target Zones’. Ideally, each tree is assessed from all sides but there are some circumstances in which this is not safe. A river bank would be a typical example.

For each tree, the following is usually recorded in a standardised way using a pre-designed form that is stored on paper or electronically. Surveyed trees are usually identified with tree tags which are physically attached to the tree. Information on a typical survey form includes:

• Species
• Position - usually expressed as map coordinates supplemented by a description
• Notes on distinctive attributes
• Approximation of age - this could be designated as categorical variables such as ‘newly planted’ ranging to ‘over-mature’
• Gaps in the crown, leaf colour, presence of dead wood and broken branches
• Presence of cracks or splits in branches
• Presence of fungus or splits and cracks in the trunk
• Presence of ivy
• Presence of leaning and a record of what it is leaning towards
• Signs of decay within the main trunk and base
• Obvious root damage
• Obvious cracks, uplifting around the tree

Classifying Tree Condition

Using the survey information, the overall physical condition of the tree can be classed. They are generally described as:

• Good - a tree that has a full crown and no signs of decay or damage; a long-life expectancy is predicted
• Fair - a tree that is mainly healthy but has some minor defects and/or thinning of the crown Poor - a tree that has some major defects or that lacks vigour; the life expectancy is short
• Dangerous - a tree that should be urgently removed because it presents a hazard
• Dead - a tree that has died and needs to be removed

Using the survey data, works on the trees can be prioritised and sensible recommendations for the management of the tree stock can be made.