HEDGEROW MANAGEMENT AND WILDLIFE A review of research on the effects of hedgerow management and adjacent land on biodiversity Contract report to Defra Edited by C J Barr1, C P Britt2,T H Sparks3 and J M Churchward4 1Barr Ecology Limited 2ADAS 3Centre for Ecology & Hydrology 4ADAS Lilac Cottage Defra Drayton Monks Wood Battlegate Road Oxen Park Alcester Road Abbots Ripton Boxworth Ulverston Stratford upon Avon Huntingdon Cambridge LA12 8HG CV37 9RQ PE17 2LS CB3 8NN CONTENTS BACKGROUND AND INTRODUCTION 1 Background to the Review 1 Summary of the problem Related research activities Objectives of the Review 1 Introduction to this Publication 2 Approach Content Updating the content HISTORY AND HEDGEROW MANAGEMENT 3 The Research Endeavour 3 Prescriptions for Hedge-Making 3 DATA ON CURRENT HEDGEROW MANAGEMENT 6 The Countryside Surveys 6 Hooper’s Survey of Hedgerows in 1990 10 Hedgerow Management Attitude Survey 10 HEDGEROW MANAGEMENT AND COSTS 12 Introduction 12 Need for Hedge Management 12 Options for Hedge Management 13 Hedge cutting Hedge planting/replanting Hedge laying and coppicing Hedge-bottom vegetation Costs of Hedge Management 17 PLANTS AND HEDGEROWS 19 Importance of Hedgerows for Plants 19 Hedgerows as a habitat for plants Species complement Hooper’s Rule Hedgerows as corridors Effects of Management 24 Woody component Hedge species composition and health Correlative studies Direct management effects on woody species Diversity of woody species Hedge-bottom flora Species composition Ground flora species diversity Evidence from correlative studies Other studies Conclusions Adjacent Land Use and Field Margins 30 Effects of hedgerows on adjacent land Effects of adjacent land on hedgerows Links with land use Effects of adjacent crop management Species movements Field margin management Recommendations 34 INVERTEBRATES AND HEDGEROWS 35 The Invertebrate Fauna of Hedgerows 35 Molluscs Spiders Insects Springtails Bumblebees True bugs Ground beetles Butterflies and moths The Value of Hedgerows for Invertebrates in Different Agricultural Landscapes 38 Ancient and planned countryside The role of hedgerows in invertebrate dispersal – corridors and networks Wildlife corridors Hedgerows as semi-permeable barriers The Impact of Hedgerow Management on Invertebrates 40 Effects of hedge cutting Effects of hedgerow restoration, replanting and protection Effects of hedge-bottom management The Effect of Adjacent Land Use on Invertebrates in Hedgerows 44 Field margins Extended field margins Enhancing Invertebrate Diversity in Hedgerows 45 Conclusions 46 AMPHIBIANS, REPTILES AND HEDGEROWS 47 General Background and the Importance of Hedges 47 Amphibians Reptiles The Effects of Hedgerow Management on Amphibians and Reptiles 48 BIRDS AND HEDGEROWS 49 The Importance of Hedgerows to Birds 49 General Hedgerow removal Hedge types and bird species richness The preference of individual bird species Adjacent land use The hedgerow as a food resource The Effects of Hedgerow Management on Bird Populations 51 General effects Specific effects Gaps in Knowledge 52 MAMMALS AND HEDGEROWS 54 Introduction 54 The Utilisation of Hedgerows by Mammals 54 Hedgehogs Shrews Bats Rabbits and Brown hares Voles Bank voles Field voles Mice Wood mice Yellow-necked mice Harvest mice Dormice Common Dormouse Foxes Martens Stoats and Weasels Polecats Badgers Deer Effects of Hedgerow Management on Mammal Populations 58 Hedgerow variables that are important in determining the diversity of mammals How to improve a hedgerow for mammals Conclusions 59 OVERALL CONCLUSIONS ON THE EFFECTS OF 60 MANAGEMENT ON WILDLIFE Introduction 60 The Impact of Different Forms of Management on Hedgerow Biodiversity 61 Hedge management Hedge shape, dimensions and density Method of trimming Timing and frequency of management activities The impact on wildlife value of non-management of a hedge Hedge-bottom management The Impact of Immediately Adjacent Land Use on Hedgerow Biodiversity 63 The Relative Importance of Hedgerows in Different Farming Contexts 64 Methods of Enhancing Biodiversity in Hedgerows 64 Priorities for Further Research 65 ACKNOWLEDGEMENTS 69 BIBLIOGRAPHY 70 BACKGROUND AND INTRODUCTION BACKGROUND AND INTRODUCTION Colin Barr Barr Ecology Limited, Lilac Cottage, Oxen Park, Ulverston, Cumbria. LA12 8HG BACKGROUND TO THE REVIEW Although research done since then has gone some way to addressing some of the policy-related issues Summary of the problem concerning hedgerows, there is now a need to re- There is an extensive literature on hedgerows, much assess the research direction and identify new of which relates to wildlife. There are also reviews priorities in the current policy climate. of various aspects of hedgerows, both general and specific, but until the first edition of this report was Related research activities published (Barr et al. 1995) there had been no Shortly before his retirement in 1992, Dr Max review which focused on the relationship between Hooper submitted a contract report to the then hedgerow management and wildlife. Osborn (1987) DOE entitled ‘Hedge Management’. This report said “FWAG (Farming and Wildlife Advisory remains unpublished but the authors of this review Group) advisers are asked many questions on hedgerow have been given permission to make use of it. management and, in the majority of cases, the advice given is Hooper’s report goes some way to meeting the based on educated conjecture, rather than drawn from objectives of this review but focuses particularly on scientific research”. As Hooper (1992) points out, the a hedgerow survey carried out in selected areas of earliest papers on hedges (1800-1845) were often England. concerned with the need to remove hedges (they were seen by some as being too plentiful and too Important background information has also come big). Up to 1960, most papers were concerned with from the results of the Countryside Surveys carried the agricultural impacts of hedgerows, and only in out by the Centre for Ecology and Hydrology the mid-1960s did interest shift to their wildlife (CEH), and its fore-runner organisations, in 1984, value. Much of this early work with a more 1990 and 1998, supplemented by a specific ecological focus was undertaken by Moore, Davis, hedgerow survey in 1993. These surveys, which Pollard and Hooper at ITE Monks Wood. were funded by MAFF and the Natural Environment Research Council (NERC), have In the mid-1990s, a summary of the research shown that after a period of marked hedgerow loss context for hedgerows was expressed by the then between 1984 and 1990 (much of which was due to Ministry of Agriculture, Fisheries and Food (MAFF) lack of appropriate management), there was no net in the research specification for earlier versions of loss between 1990 and 1998, although the quality of this review: hedgerows (and associated vegetation) continued to decline. As a policy matter of importance to all “Hedges are important for flora and fauna. They may be Government Departments, it is important to know managed in a variety of ways according to the needs of the what the wildlife consequences of this trend may be. farm and sometimes local custom. The benefits of different management practices for wildlife can vary both as a result of the methods used and the timing of the operations. The OBJECTIVES OF THE REVIEW nature of the adjacent land use can also have an important effect on the biodiversity of the hedge. MAFF provides grants The specific objectives of the review were laid out for some forms of hedgerow management both as part of the clearly in MAFF’s original research specification, as Environmentally Sensitive Areas Scheme and the Farm and follows: Conservation Grant Scheme. The wildlife value of hedgerows “A review of previous and current research is required: is also a consideration in other MAFF schemes such as the Habitat Scheme and set-aside. In order to inform the 1. To assess the impact of different forms of management development of its policies, MAFF needs a report which pulls on hedgerow biodiversity, e.g. closely cut, cut into an A- together the knowledge currently available on the wildlife shape or square topped, laid or coppiced. The impact value of hedges under different circumstances.” on wildlife value of non-management (i.e. development into relict hedges) also needs to be taken into account as does the timing of any management activities. HEDGEROW MANAGEMENT AND WILDLIFE 1 BACKGROUND AND INTRODUCTION 2. To assess the impact of immediately adjacent land use between the two research organisations with on hedgerow biodiversity, e.g. intensive arable, arable individual members of staff being given with uncropped land alongside the hedge, permanent responsibility for different research areas, and hence grass, woodland, water-course. different sections within the report. This approach risked duplication between sections and an ‘editorial 3. To assess the relative importance of hedgerows for team’ from both organisations took responsibility wildlife in different farming contexts, e.g. arable versus for combining contributions into a single report. grassland, lowland versus upland. This will need to take account of varying local hedgerow practices, e.g. During the course of the review, authors extracted Devon pastoral compared with West information from many hundreds of papers in Midlands/Marches pastoral. scientific journals, magazines and elsewhere. They also read many hundreds more and, where 4. To identify methods of enhancing biodiversity in hedges appropriate, these have been included in the