Case Studies - Challon Hall Wood, Leighton Moss, RSPB North West
RSPB began formally to address the issue of tree safety on its 150+ nature reserves in 2003. By early 2004 an internal code of practice was issued outlining the process by which each reserve would be assessed, and the level of competence of the Tree Safety Advisors who carry out the assessments.
Any such process balances the need for safety with the conservation or recreation priorities of the RSPB on a risk assessment basis. Ancient and decaying trees are often a uniquely valuable habitat for wildlife and some of our reserves have a target to increase the percentage of dead wood! However poor the condition of the tree, RSPB has taken the view that it expects remedial action will only be necessary where there is a clearly perceived risk to life or property.
Each Region or Country established the order of priority in which reserves and other property will be initially assessed by a Tree Safety Advisor (TSA). This was done by taking into account the size of the reserve or property, location, number of visitors and amount of tree cover. Initially only 9 TSAs were trained by external specialist arborists. This number has doubled using internal specialists who attended the initial training and have since developed a 2-day course for RSPB staff. Further training is planned to ensure all Regions and Countries have adequate resources to inspect at the appropriate intervals.
The site managers, working with the TSA, then split their site into risk zones to enable the priority areas to be assessed first and most often. The risk zones are areas of the reserve or property assessed for the hazards presented by trees.
When designating risk zones areas where people congregate or stay may present greater risk than paths or trails where people pass through. Risk zones are currently designated as:
| High risk | e.g. close to major public gathering areas, buildings, hides and viewing points, car parks; alongside busy footpaths, public roads, railway lines etc. and other well visited areas of a property |
| Medium risk | e.g. other paths and bridleways in regular but not high use; less well visited or worked in areas of reserves etc |
| Low risk | e.g. farmland, woodland or other parts of the reserve away from paths and tracks or only lightly visited |
The Leighton Moss reserve in RSPB North West presented some of the most challenging areas for assessment. The work required after the assessment was the largest amount from a single survey so far. The assessment of one part of the reserves holdings – Challon Hall Wood – is given as an example below.
Introduction and Background
The sample from the report for Challon Hall Wood forms part of the overall Tree Hazard Assessment Report for RSPB’s Leighton Moss Reserve. Dave Barrett, Regional Safety Adviser, completed the assessment in October 2004. Each section of the report comprises an overall Risk Zone Map, supported by more detailed Specific Tree Area Maps and Recording Forms. Risk Zones were initially estimated on the amount of usage by traffic and people. Once the tree hazard assessment was complete the Risk Zone was reviewed taking account of any hazardous trees found and either confirmed or changed accordingly. In most cases, the initial Risk Zone assessments were accurate.
Each designated Tree Area was surveyed for hazardous trees. Most of the Tree Areas tend to be narrow zones (less than 20 m wide) alongside roads, tracks and paths. Trees requiring future monitoring are recorded on Form 1, Specific Tree Records and trees requiring obvious remedial work and will pose no further risk once the action is completed are recorded on to Form 2, Area Tree Recording Form.
An example of each of these is shown. The Overall Risk Zone Map covers the Challon Hall section of the reserve at Leighton Moss. The zones identified here are then numbered, and the example below gives the detail of Tree Area 12. In this area some remedial work was recommended and recorded on Form 2. A number of trees were recommended to be left but their condition was recorded and a further inspection is required in 12 months time (or after severe weather). An example of one such individual tree record is given on Form 1.
Whilst this process has seemed complex and time consuming, this particular site presented RSPB with some of its most difficult trees to assess. A typical reserve has taken 2-3 days to survey and report on the high risk zones, with a further 3-4 days to cover the remaining medium risk zones for the first year. Work in subsequent years is expected to reduce as the bulk of the hazardous trees are either made safer or monitored more closely.
This case study was written by Royal Society for the Protection of Birds and was published in February 2005
This website entry was last updated on 9 November, 2006
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