Letter

Sir, I am grateful for the opportunity to respond to the letters from Mark Chester and Dr Jon Heuch. I do so on behalf of the CAVAT Executive. Firstly, before getting into any details, I feel it will be helpful to establish the key distinctions between CAVAT and the Council of Tree and Landscape Appraisers (CTLA) methods. CAVAT has its origin in a single conversation at the Arboricultural Association conference on tree valuation in Milton Keynes in 1997, between the writer, the chairman for the day Jonathan Hazell and Jon Stokes of the Tree Council. We agreed that UK arboriculture needed a system for tree valuation as robust and effective as the Council of Tree and Landscape Appraisers (CTLA) methods were in the USA. That need has guided the development of CAVAT to the present day. Both CAVAT and the CTLA trunk formula method are extrapolated and depreciated cost replacement methods (DRC) intended for amenity trees. However, while the CTLA methods focus solely on compensation, with a background in real estate valuation, CAVAT is designed to express a tree’s asset value, with multiple purposes including but not limited to compensation value. Equally significantly CAVAT uses amenity not with the limited meaning of “trees not grown as a crop” but within the framework of the trees as public amenities, as established in the Town and Country Planning Act 1991, sections 197 and 198, and more recently in the National Planning Policy Framework at paragraph 170 (b) which specifically establishes trees as natural capital. CAVAT’s main aim is to enable the management of urban trees as assets, an essential element of urban forestry. For the curious, an expression of how that theory should be put into practice, based on an early version of CAVAT, may be found in Case Study 9: Establishing and Justifying the Tree Budget in Trees in Towns II (Britt and Johnson, 2008). A current example of that ambition, now put into practice, is given in Case Study 2 of our paper (namely the Doick et al. (2018) paper, hereafter referred to as “the paper”). It sets out how a London borough adopted CAVAT as part of an asset-based approach to highway tree management and the benefits that followed. Turning to the letter from Mark Chester first, having begun with a brief compliment to the authors of the paper he moves on to argue that use of CAVAT is unnecessary or at least nearly duplicates what is available and better expressed in the CTLA methods. This is somewhat at odds with the UKI – RPA Guidance Note 1, which introduced the CTLA methods to the UK, where the joint authors, including Dr Heuch, position it alongside existing methods. He continues by questioning the absence of reference to “ATA”; the acronym stands for the Adjusted Trunk Area formula, explained in the Guide for Plant Appraisal ninth edition (CTLA 2000). It is the means by which valuations using the trunk formula method are systematically limited for trees with a diameter exceeding 75 cm. The rationale is stated: “like many aspects of real-estate valuation trees reach an Arboricultural Journal 2020, VOL. 42, NO. 1, 56–60 https://doi.org/10.1080/03071375.2020.1725342