BD2111 SID 5 FINAL Aug 2010

General enquiries on this form should be made to: Defra, Science Directorate, Management Support and Finance Team, Telephone No. 020 7238 1612 E-mail: [email protected] SID 5 Research Project Final Report Note In line with the Freedom of Information Act 2000, Defra aims to place the results Project identification of its completed research projects in the public domain wherever possible. The BD2111 SID 5 (Research Project Final Report) is 1. Defra Project code designed to capture the information on the results and outputs of Defra-funded 2. Project title research in a format that is easily Trends, long term survival and ecological values of publishable through the Defra website. A hedgerow trees: development of populations models to SID 5 must be completed for all projects. inform strategy. This form is in Word format and the boxes may be expanded or reduced, as 3. Contractor Forest Research appropriate. organisation(s) ACCESS TO INFORMATION The information collected on this form will be stored electronically and may be sent to any part of Defra, or to individual researchers or organisations outside Defra for the purposes of reviewing the £ 51226 project. Defra may also disclose the 54. Total Defra project costs information to any outside organisation (agreed fixed price) acting as an agent authorised by Defra to process final research reports on its 5. Project: start date ................ 05 January 2009 behalf. Defra intends to publish this form on its website, unless there are strong reasons not to, which fully comply with end date ................. 31 July 2009 exemptions under the Environmental Information Regulations or the Freedom of Information Act 2000. Defra may be required to release information, including personal data and commercial information, on request under the Environmental Information Regulations or the Freedom of Information Act 2000. However, Defra will not permit any unwarranted breach of confidentiality or act in contravention of its obligations under the Data Protection Act 1998. Defra or its appointed agents may use the name, address or other details on your form to contact you in connection with occasional customer research aimed at improving the processes through which Defra works with its contractors. SID 5 (Rev. 3/06) Page 1 of 23 6. It is Defra‟s intention to publish this form. Please confirm your agreement to do so. ................................................................................... YES NO (a) When preparing SID 5s contractors should bear in mind that Defra intends that they be made public. They should be written in a clear and concise manner and represent a full account of the research project which someone not closely associated with the project can follow. Defra recognises that in a small minority of cases there may be information, such as intellectual property or commercially confidential data, used in or generated by the research project, which should not be disclosed. In these cases, such information should be detailed in a separate annex (not to be published) so that the SID 5 can be placed in the public domain. Where it is impossible to complete the Final Report without including references to any sensitive or confidential data, the information should be included and section (b) completed. NB: only in exceptional circumstances will Defra expect contractors to give a "No" answer. In all cases, reasons for withholding information must be fully in line with exemptions under the Environmental Information Regulations or the Freedom of Information Act 2000. (b) If you have answered NO, please explain why the Final report should not be released into public domain Executive Summary 7. The executive summary must not exceed 2 sides in total of A4 and should be understandable to the intelligent non-scientist. It should cover the main objectives, methods and findings of the research, together with any other significant events and options for new work. The main objective for the study has been to develop a population model for isolated hedgerow trees in order to review, and if necessary amend, the 2006 HAP targets for hedgerow trees, in particular the number of young trees required to ensure that the isolated hedgerow tree population remains stable or increases. The second main objective was to collate and review existing information on the biodiversity value of hedgerow trees with emphasis on invertebrates, comparing where possible the role of isolated hedgerow trees and lines of trees. With the exception of more limited development of an expert decision key in favour of quantitative models, the objectives have been met and the outcomes discussed at the Stakeholder Workshop held at Forest Research, Alice Holt Lodge on 24 July, 2009. Discussion points and suggestions from the Workshop have been incorporated in the results and recommendations in the report. The key outcomes and conclusions are: The modelling component has provided both predicted figures for the rates of recruitment of hedgerow trees needed to retain the current population and has also indicated the level of sensitivity of these parameters to changing assumptions, including management and human intervention. Conclusions from various sources, commencing with the concerns expressed in the 1951 Forestry Commission study and subsequently in recent Countryside Surveys and by the Tree Council, all agree that hedgerow trees in Great Britain are in sharp decline. In bringing these sources together, the present study is the first to model the extent of the decline and to provide quantitative indications of the necessary recruitment rates to halt and, if possible, to reverse the decline. Simulations from the model suggest that concerted action is needed both to accelerate recruitment of isolated hedgerow trees and, equally important, to reduce the rate of mortality in the older cohorts of those trees. The numbers of hedgerow trees needed „just to stand still‟ are demanding: Annual recruitment of around 30,000 trees across GB is needed to stabilise the current population of 1.60 m isolated hedgerow trees, which is already reduced from the 1.67 m trees recorded in the CS2000 (adjusted downwards from the widely published figure of 1.8m trees); In relation to age structure/size of trees to ensure sufficient recruitment of new trees, an estimated 45% of hedgerow trees need to be <20 cm dbh, which compares unfavourably with the recorded value of 19%. This further emphasises the lack of recruitment at the required level needed to maintain a viable population of isolated hedgerow trees; SID 5 (Rev. 3/06) Page 2 of 23 Only 15,000 trees are currently being recruited annually. On this basis, the model projects a drop in total isolated hedgerow trees to as low as 1.05m trees over the next 50 years; From discussions at the Workshop in July 2009, it appears that mortality of older trees is accelerating in some areas of the country, although the cause of this mortality is unclear. There is some evidence that concerns about Health & Safety from unhealthy trees arising from the Poll vs Bartholomew judgement may lead to premature felling of trees where there uncertainty about their stability; The dominance of ash and oak in hedgerow tree populations may compromise future recruitment and survival trends, especially as these two species appear to be showing evidence of increasing decline in relation to climate change. Ecological values directly applicable to isolated hedgerow trees have been difficult to assess and quantify. There is remarkably little verifiable and direct study on the absolute and relative roles of hedgerow trees as ecological features of the landscape. Overall, the indications were that isolated hedgerow trees have distinct and, sometimes, unique ecological values that would contribute significantly to the ecosystem services offered by this resource. Key findings were: Trees within a hedgerow are likely to encourage a wider range of invertebrate species than would otherwise be the case both by provision of greater niche availability and provision of shelter; Studies of moths by Merckx et al and of Diptera by Peng et al have shown clearly that abundance and diversity of the two invertebrate groups are enhanced by proximity to hedgerow trees, with further linkage to the width of the hedge and field borders; Inferences on interactions of BAP priority species with hedgerow trees suggest that many species benefit from the presence of this ecological resource, by virtue of structure and stability as well as enhanced food resources; Bats and birds benefit from hedgerow trees both as roosts/breeding/feeding sites and as connecting features to facilitate movement through the wider landscape. In particular, the „darkness quality‟ provided by canopy shading is likely to extend the foraging period by bats in the early evening as well as providing perches for some species. Simulations of the recruitment and loss rates of isolated hedgerow trees, therefore, provide a quantitative measure of the scale of losses and the necessary replacement rates to be able to maintain or increase this valuable resource. While the ecological roles and values of hedgerow trees are regarded as positive, albeit with relatively few specific studies to quantify this contribution, there are many other attributes of hedgerow trees that support their retention in the landscape. Landscape values Other than the ecological values that have been the subject of review in this project, a related but highly valued attribute of hedgerow trees is the perception of how they fit into the wider landscape. This has been the subject of Landscape Character Assessment through the Countryside Agency with Natural England, Scottish Natural Heritage and Countryside Council for Wales. Information is brought together by the Landscape Character Network. The British countryside has been divided into a series of National Character Areas, reflecting the particular landscape characteristics of each area. Some of these are highly relevant to the current topic of hedgerow trees and have been highlighted by Stokes & Hand (2004).

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