The author of CAVAT is Chris Neilan
Chris is an arboriculturist who has worked in a planning context in the public sector for Epping Forest District Council since 1989 with responsibility for tree protection and landscape issues. The district of Epping Forest is situated immediately North East of London, within the county of Essex, U.K. Having been a teacher for a short while, Chris also has experience as a local authority tree manager and as a tree surgeon in public and private practice.
Chris has lectured and taught widely on CAVAT and other issues within the UK and abroad.
In addition to CAVAT Chris has also pioneered innovative ways of working with the community to encourage wider participation in the protection of trees and landscape and so also to give the work of the Local Planning Authority greater legitimacy. For more information on use of “Soft Power” in Epping Forest District follow this link:
The development of CAVAT has been greatly helped by input from individuals across the UK, and particularly a working group set up by the London Tree Officers Association (LTOA) and also the LTOA Executive Committee. See Acknowledgements.
The author is grateful to:
· past and present colleagues in Epping, including: Russell Horsey, for his past and continuing advice and assistance, Tracy Clarke for her trial survey in Theydon Bois, Stuart Forgione, Alex Sleet and Sarah Creitzman;
· his daughters Kate and Emily Neilan for technical assistance;
· the members of the CAVAT Steering Group;
· the members of the LTOA and ETaLOG user groups and in particular to Dave Lofthouse, Ryan Nixon Paul Maher, Becky Hesch and Matthew Searle for their encouragement, advice and assistance in developing and trialling the CAVAT methods;
· Jim Smith, London Trees and Woodlands Framework Manager, for his invaluable support, advice and advocacy:
· Andy Tipping, London Borough of Barnet, for having sufficient faith in CAVAT to put it into practice, championing the project as LTOA Chairman and for advocating the inclusion of population density as an improvement to the method and indicating the means to do so;
· Jake Tibbetts and Andy Lederer of the London Borough of Islington for demonstrating the potential of CAVAT as a management tool;
· the several nurseries that assisted with information for the author’s research on unit costs, and to Mike Glover and Keith Sacre of Barchams in particular for their contributions to the work of the LTOA user group and their encouragement;
· Jon Stokes of the Tree Council, and Jeremy Barrell among many others for their kind advice.
The author also gratefully acknowledges the work of Jeremy Barrell on Safe Useful Life Ex[ectancy, (SULE), which is incorporated into CAVAT, the pioneering work over many years by Rodney Helliwell on the assessment of the monetary value of trees in the UK, and that of Scott Cullen in the USA.
Any deficiencies in the work of course remain the author’s own.
Development of CAVAT
Chris Neilan found that he needed to express the monetary value of damaged or destroyed trees when giving evidence as part of following through with prosecutions for offences under Tree Preservation Order (TPO) regulations.
He had been trained in the use of the Helliwell method, but realised that he could not give evidence under oath based on it, Instead he adopted the simpler approach of using multiples of the value of semi-mature trees, which the magistrates found understandable and helpful. His experience formed the basis for a short article published by the Arboricultural Association (AA) in its magazine. He also realised that tree valuation should be a method for influencing care and management of the public tree stock, as well as for compensation cases.
Chris was invited to speak at an AA seminar at Milton Keynes (1998) on aspects of tree value, chaired by Jonathan Hazell, where he presented a paper on the theoretical basis of potential approaches to valuation. Other speakers included Giles Nance, Liverpool City Council, Rodney Helliwell & Jon Stokes. Jon Stokes reported on his experiences in the US, including the use of the trunk formula method to give a value for trees in relation to compensation, giving examples relating to street trees. In conversation afterwards Chris undertook to develop a new tree valuation method to be used in the UK. Having reviewed the other possibilities he decided to base his method on the trunk formula approach as the most robust and also the most practicable, otherwise starting from first principles.
To achieve this Chris undertook extensive research on nursery stock production across UK, including the influence on unit costs of production techniques, (e.g. open ground/containerised/ container grown), and other variables including size, species and costs of planting. This led to the decision to use a basket of trees to generate a unit area cost for robustness, not individual species. Chris used this work to generate the unit area value, which is the basis of CAVAT.
Chris then added adjustments for Accessibility, Functionality & the Amenity/Appropriateness factors. Functionality is a new concept, and is the element of CAVAT that gives it its power as a management tool. He also developed an alternative “Quick” method for use with existing databases to enable “Asset Value Management” of the public tree stock.
Chris was invited to present a paper on his method, then called “AVMT” to the AA conference of 2003, with a very positive reception. Amongst the audience was Dave Lofthouse, L.B. Merton, who arranged that Chris be invited to present a paper to the next London Tree Officers Association (LTOA) quarterly meeting. This led to formation of LTOA working party to assess the work. Of those who assisted as part of that Ryan Nixon and Russell Horsey deserve special mention as ever-present.
Involvement of LTOA Working Party
It was agreed with the working party that Chris would present to its members the complete research and formulation of methods to date, to allow them to take a view on the method as a whole, give any advice they felt necessary and in due course to report to the LTOA executive committee as to the appropriateness of recommending its adoption across London.
During its discussions decisions on how to generate Unit Area Value UAV (ie using a basket of stock of commonly planted street trees, at 12/14cm girth size, using containerised stock), were all validated. The group offered to undertake a check of the most commonly planted stock across London to improve robustness, which was done and the results incorporated. In discussions it was agreed that UAV should be updated with national inflation, not nursery stock prices (these were considered to be too variable for the proposed use as an asset management tool). Having researched the possibilities Chris chose RPIX as most appropriate index of U.K. inflation.
As originally proposed CAVAT had no means of accounting for the extra value of trees in cities. The group thought this to be necessary and that the extra cost of planting in cities was the most likely means. Members of the WP undertook a survey of street tree planting costs across London and from it developed zones of up to 2.5x basic UA values. However this was ultimately rejected by the LTOA executive as insufficiently robust. Jake Tibbetts and Andy Tipping suggested an alternative approach based on population density, having the advantage of the official population statistics as a basis. From that suggestion Chris researched and developed an appropriate methodology, introducing weighting for different population densities from 100- 250%, naming this the Community Tree Index (CTI). He then produced the national CTI factor list with assistance from Andy Tipping.
The WP agreed the Accessibility and Functionality factors with no changes.
They also agreed the methodology of the positive and negative Amenity and Appropriateness factors with no changes. As part of the Executive Committee input Andy Tipping later suggested the addition of coherent management of areas of pollards as an additional positive factor. Andy also agreed to trial Quick Method as part of his stock survey across the L.B. Barnet. Finally, it was Andy’s view that the name used by Chris, AVMT, was not a good one. In response Chris invented CAVAT (Capital Asset Value for Amenity Trees), retaining AVMT as the name for output of CAVAT, that is asset value management for amenity trees.
Chris was invited by the Consulting Arborists Society (CAS) to address a tree valuation seminar in Bath, November 2005, as second speaker to Scott Cullen. Scott presented the range of methods used by the Council of Tree and Landscape Appraisers in the USA. This seminar initiated the work that led to the publication of the UK guidance on tree valuation by the UKI RPAC (U.K. and Ireland Regional Plant Appraisal Committee). Scott felt that a major problem with the (then) AVMT was its non- inclusion of an adjustment for life expectancy. On consideration Chris agreed, and developed the Safe Life Expectancy (SLE) adjustment, but on a new basis, using SULE and his original research on an appropriate weighting
Asset Value Management for Trees (AVMT)
A population of urban trees in streets or parks is an important community asset. To plant it, maintain it and manage it requires resources. Being able to place a financial value on the trees, albeit one that is nominal, allows managers to demonstrate that they are using resources beneficially; if enables Councillors or elected officials to judge how well resources are being used and it helps to give confidence to the community that the tree asset is being properly looked after.
AVMT allows targets to be set, based on past performance. It allows analysis of the relative strength of the urban tree stock across borough, town or city, and aids decision making.
CAVAT is able to work at different levels; local decision making, financial provision and strategic and setting strategic policy.
Local Decision Making
Cost benefit analysis using projections of results alternative pruning regimes; setting of information levels, e.g. in subsidence cases.
A setting of budget provision in relation to value of asset:
Monitoring performance in terms of changes in value of asset.
Analysing outcomes of alternative policies:
Analysing strengths and weaknesses of tree stock;
Approaches to Tree Value
CAVAT values the tree stock in terms of their extrapolated and adjusted replacement cost and their relative degree of public amenity. This is related to an approach taken in the United States by the Council of Tree and Landscape Appraisers’ (CTLA), the Trunk Formula method, which has been adapted for the UK by Adam Hollis (Amenity Tree Valuation, Provisional Guidance Note, 2007). However the output of the CTLA Trunk Formula Method is framed in terms of the value of the tree to its owner, whether that might be a private individual or a public authority.
In CAVAT the value of the mature tree is extrapolated from the value of a square centimetre of the cross sectional area at breast height. This in turn has been derived form the average installed cost of a basket of commonly chosen street trees, according to the cost of a square centimetre of stem cross section.
Alternative approaches to tree valuation include measuring the output of the trees either in terms of their visual amenity or their measurable outputs in terms of benefits to the community.
The Helliwell method, developed in the UK, values the visual output of trees. i-Tree, based on work in the 1980’s by the US Forestry Service and subsequently developed, expresses the value of the trees in terms of their carbon sequestration, building energy use reduction, absorption of carbon emissions etc. In i-Tree, trees are given a structural value using either the CTLA trunk formula method or, in the UK, CAVAT.
Uses of CAVAT
CAVAT has two main purposes.
1. Managing trees as assets (Asset Value Management for Trees – AVMT)
2. Valuation of individual trees
To manage trees as assets the CAVAT Quick method is generally used; the CAVAT Full method is for cases where a tree is being scrutinised individually.
A CAVAT valuation will reflect a tree’s contribution to the general public good, that is as a public amenity, not its value as a private asset to its owner. Trees on private land may be valued using CAVAT but the result will be different from a valuation aimed at reflecting a tree’s value to the owner.
The primary, intended use of CAVAT is to allow local authorities to incorporate asset value management into their control of their own tree stocks, whether in streets, parks or other open spaces. Users will normally incorporate the CAVAT quick method into their routine tree surveys. Alternatively they could value a proportion of their stock and extrapolate an overall value. Advice on how to do this is available within the CAVAT user docs available from www.ltoa.org.uk.
For further information on asset value management for trees see AVMT.
The CAVAT full method will value individual trees, for purposes of comparison or in relation to insurance claims etc. CAVAT is included for this purpose in the Joint Mitigation Protocol, (JMP) negotiated between the London Tree Officers Association and the insurance industry. Use of CAVAT for individual tree valuation may also be useful where trees are to be removed as part of development of public areas or road improvements to help determine necessary compensation, and help ensure that adequate resources are available for realistic replacement. For an example of this see the Bristol case study. CAVAT is now being used to provide the structural value of trees in i-Tree.
Who is able to use CAVAT?
CAVAT is for professional use. CAVAT documents and instructions are freely available, however, to calculate a valuation with confidence and accuracy a user needs a level of understanding of trees and of how they function that would normally be exclusive to a professional Arboriculturist. Most particularly a user needs to be aware of the normal form and growth patterns of difference species of trees, predict their life expectancy and be able to judge whether a particular tree is functioning normally or not. To use CAVAT accurately and to understand its purpose as a management tool it is essential that would be users of CAVAT have had appropriate training. Anyone interested is welcome to contact the author for availability of training opportunities.
CAVAT Steering Group
CAVAT - Where are we?
Tested and agreed as fit for purpose by LTOA working group and LTOA executive, (May 2008).
Featured as an exemplar in Trees in Town II (DCLG Feb 2008), in the case study, “Establishing and Justifying the Tree Budget”.
Specified for use in subsidence cases in LTOA “Risk Limitation Strategy” (3rd edition, May 2007).
Incorporated as the agreed method in the Joint Mitigation Protocol (LTOA May 2008), to set evidential levels in tree related subsidence cases.
Referenced in Tree and Design Action Group “No Trees No Future” 2008
Approved as fit for purpose, Forestry Commission Research Note “Street Tree Valuations systems” April 2009.
Referenced in BS3998: 2010 tree work recommendations.
The CAVAT Steering Group is currently the author, Chris Neilan with:
· Becky Porter, (LTOA secretary)
· Russell Horsey, Deputy Director ICF (as of October 2012)
· Fergus O’Carroll, Fingal County Council, Irish Republic
· Keith Sacre, Barchams
· Matt Searle, Essex County Council/ ETaLOG
· Jim Smith, Forestry Commission/ Mayor of London’s Office
· John Stokes, The Tree Council
· Jake Tibbetts, London Borough of Islington/ LTOA
· Andy Tipping, London Borough of Barnet/ LTOA
· Matt Vaughan, Dudley Borough Council/ MTOA.