The Ecology and Conservation of the Southern Damselfly (Coenagrion mercuriale – Charpentier) in Britain R&D Technical Report W1-021/TR B Purse Research Contractor: University of Liverpool Publishing Organisation Environment Agency, Rio House, Waterside Drive, Aztec West, Almondsbury, Bristol, BS32 4UD. Tel: 01454 624400 Fax: 01454 624409 Website: www.environment-agency.gov.uk Environment Agency 2002 ISBN 1 857 057 910 This report is the result of work jointly funded by the Environment Agency, English Nature, Countryside Council for Wales and University of Liverpool. All right reserved. No part of this document may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior permission of the Environment Agency. The views expressed in this document are not necessarily those of the Environment Agency. Its officers, servants or agents accept no liability whatsoever for any loss or damage arising from the interpretation or use of the information, or reliance on views contained herein. Dissemination Status Internal: Released to Regions External: Public Domain Keywords Southern Damselfly, habitat, larvae, chalkstream, heathland grazing. Research Contractor This document was produced under R&D Project W1-021 by: Bethan Purse, Population and Evolutionary Biology Research Group, School of Biological Sciences, University of Liverpool, PO Box 147, Liverpool, L69 3BS. Tel: 0151 794 5023 Fax: 0151 794 5094 Environment Agency’s Project Manager Tim Sykes, Southern Region Preface - Purposes (and use) of this Report The Biodiversity Convention, signed by Britain at the Rio Earth Summit, in June 1992, required that national programmes for the conservation of biological diversity were developed. In 1994, the UK Biodiversity Action Plan was produced (HMSO, 1994), that initially selected and provided action plans for 14 key habitats and 116 key species of top conservation priority. The Southern Damselfly was among this list and, in 1995, a species action plan was produced for this species. A Steering Group was inaugurated in April 1997 to co-ordinate and oversee the implementation of this Species Action Plan (SAP). Represented on the group are the Environment Agency, the Countryside Council for Wales, English Nature, the British Dragonfly Society, The Wildlife Trusts. Academics from Liverpool University have been co-opted onto the Group. The SAP highlighted the need for further research into the ecological requirements of this species in Britain (Action 5.5.1). This resulted in the Steering Group commissioning, in1998, a PhD study on the ecology and conservation of the Southern Damselfly. A copy of the thesis is available as R&D Project Record W1-021/PR. This R&D Technical Report aims to summarise information from the PhD, in an accessible form, on the following; S Life cycle and development of the Southern Damselfly (Chapter 3) S Large-scale habitat use (across sites – Chapter 2) and small-scale habitat use (within a site by adults and larvae – Chapter 4) S Reproduction, mortality and dispersal of the mature adult Southern Damselfly (Chapters 5 and 6). The main findings of a chapter are contained in a summary section at its beginning. In view of this information, Chapter 7; S lists habitat attributes required by the Southern Damselfly in Britain S recommends management for achievement of favourable habitat condition R&D Technical Report W1-021/TR S advises on monitoring of the Southern Damselfly Boxes in each chapter provide definitions of technical terms and site examples. Odonates and plants are referred to by their latin names with the common name provided in brackets where possible on first mention of a species. For clarity, extensive description of methodology and statistical analyses are not included in this report unless relevant and are detailed in W1-021/PR. In addition, only the most relevant references are cited in the text and listed in the table of references. More detailed references can be found in W1-021/PR. In this report, the symbol is used to indicate the sample mean (rather than the population mean as is conventional). Means are presented M the standard error (s.e.). The Steering Group commisioned a second PhD which began in 2000 to investigate the ecology of the Southern Damselfly in its chalksteam-fen habitats. This is also being managed and co-funded as an R&D project (W1- 066) R&D TECHNICAL REPORT W1-021/TR EXECUTIVE SUMMARY The Southern Damselfly is rare in Britain and Europe and has declined by around 30% in Britain this century. It occupies two rare biotopes in Britain – small streams on heathlands and old water meadow ditch systems on chalkstreams, both of which have undergone considerable fragmentation this century (though a few sites are found on poor fen). Prior to this project, there had been numerous, independent studies of the ecology of the Southern Damselfly but these lacked standard methodology or aims and, in 1995, the Species Action Plan for this species highlighted the need for further research into its ecological requirements in Britain. This R&D Technical Report presents the results of a PhD study on the ecology and conservation of the Southern Damselfly commissioned by the UK Steering Group in 1998. The life cycle and development of this species were investigated as well as reproduction, mortality and dispersal of the mature adult stage. Large-scale habitat use (across sites) and small-scale habitat use (within a site by adults and larvae) were examined. In light of these results, this report recommends management (and monitoring) regimes for the Southern Damselfly in Britain. The findings of this report on aspects of the species’ basic ecology can be summarised as follows: S The Southern Damselfly requires two years for larval development in Britain S The flight period of the adults is shorter in Britain than in Europe and daily emergence depends on climatic variables. S Mortality was consistently low in the mature adult stage and at emergence but high in the egg and immature adult stages. S Climatic variables influenced mature adult survival, whether individuals were present at the breeding site and whether they engaged in reproductive activity given that they were present S The Southern Damselfly was found to be relatively sedentary but the field observed dispersal rate was probably sufficient for colonisation events and exchange of individuals to occur frequently between populations in large clusters of sites in Britain. S Soft-stemmed, submerged and semi-emergent herbs were favoured for oviposition whilst tall emergents with rigid upright stems were favoured for emergence. S Dispersal seemed highly dependent on aspects of landscape structure. The Southern Damselfly was found to be restricted in its national and global distribution probably by climatic variables including temperature and by the availability of its biotopes. It is further restricted within these biotopes because it is stenotopic i.e. highly sensitive to a number of habitat factors such as sunlight, shade, water flow and aquatic and bankside vegetation structure. The physical, vegetation and chemical features common to British Southern Damselfly sites can be summarised as follows: Physical features S Low altitude and gently sloping ground (< 10% slope) S Inorganic substrate overlaid with shallow organic peat or silt S Shallow narrow waterbodies on heathlands, small ditches on chalkstreams S Slow to moderate water flow S Proximity to springs or groundwater ensuring permanence of water flow and stable thermal regimes with high minimum winter temperatures. Water arising from soft deposits of sandstone, limestone and clay Vegetation features S Remoteness from improved agriculture preventing eutrophication and encroachment of invasive tall emergents and algae R&D TECHNICAL REPORT W1-021/TR 1 S Open and exposed watercourses S Medium to high cover of submergent and emergent stream vegetation (low to medium height) S Herbaceous, perennial stream vegetation S Shelter on bankside and sometimes within the stream (e.g. Myrica gale). Chemical features S Dystrophic to oligotrophic nutrient conditions S Unpolluted water S High oxygen concentrations Many of these features seem to reflect a requirement for a thermally advantageous microclimate, restricting the Southern Damselfly to an early successional stage of its biotopes. This requirement is also reflected in the features selected by individuals at a small-scale - during emergence and oviposition. In light of these findings on the ecology and habitat requirements of the Southern Damselfly in Britain, the following recommendations are made for management; S Moderate grazing regimes should be used that reduce establishment of scrub and invasive emergents with heavier animals such as cattle or horses to produce poached watercourse margins and a diversity of tussock structure. S Intermittent selective hand clearance of vegetation is recommended within watercourses in both biotopes. Cut vegetation from clearance should be deposited on only one bank or area of the site. S On chalkstream ditches, hand-cutting of bankside herbs and rushes may be beneficial within short stream sections and on a rotational basis. S Burning should only be employed in small patches on large sites, when there is strong evidence that burning has produced a positive effect in the past and when other methods of maintaining open heathland have proved unsuccessful. Burnt vegetation should be removed from the site to minimise pollution. S Drop board weirs can be used on water meadow ditch systems to maintain water availability through spring and summer. S Canalisation, drainage, abstraction and dredging of watercourses and peat cutting should be avoided near watercourses occupied by the Southern Damselfly. S Nutrient run-off from farmland should be minimised in catchments of watercourses containing the Southern Damselfly populations by minimising the use of artificial fertilisers. Agricultural land, adjacent to Southern Damselfly sites in Britain should be used extensively or a buffer strip of extensively used land, of at least 20m, should be maintained around watercourses.