A review of the evidence on the interactions of beavers with the natural and human environment in relation to England (NEER017) First edition – November 2020 www.gov.uk/natural-england Natural England Research Report NEER017 1 Citation This report should be cited as: Howe, C.V. (Ed) (2020). A review of the evidence on the interactions of beavers with the natural and human environment in relation to England. Natural England Evidence Review NEER017. Peterborough: Natural England. Author for correspondence: [email protected] External expert reviewers Dr Dean Waters –University of York Prof John Gurnell – Queen Mary University of London Prof Richard Brazier – University of Exeter Natural England Project Manager Julie Eaton Natural England Worcester County Hall Spetchley Road Worcester WR5 2NP [email protected] Acknowledgements Particular thanks are due to the three external reviewers, Richard Brazier, John Gurnell and Dean Waters for their detailed, constructive comments, suggestions and information which greatly improved the report. In addition, we are grateful for helpful comments on earlier drafts from Natural England colleagues Pete Brotherton, Andy Brown, Alastair Crowle, Julie Eaton, Elaine Gill, Matt Heydon, Delphine Pouget and Dave Stone who also provided valuable methodological advice and quality assured the report. We also thank the following additional Natural England staff for their inputs through discussion and/or provision of advice, information and support: Hazel Carter, Richard Clarke, Suzanne Crutchley, Mike Day, Alan Drewitt, Emma Goldsmith, Richard Jefferson, Kate Morris, Mina Patel, Ben Payne, Suzanne Perry, Mel Sherwood, Giles Wagstaff and Ben Yexley. Natural England Research Report NEER017 2 The following external people have contributed to the review report through discussion and/or provision of advice, information and data for which Natural England is very grateful: Roger Auster (University of Exeter), Roisin Campbell-Palmer (Independent consultant), Sophie Common (Zoological Society of London), Helen Donald (Zoological Society of London), Martin Gaywood (NatureScot), Hugh Graham (University of Exeter), Jeanette Hall (NatureScot), Duncan Halley (NINA), Alex Inman (Independent consultant), Scot Mathieson (SEPA), Allan McDevitt (University of Salford), Andy Moore (Cefas), Mark Mulligan (Kings College London), Alan Puttock (University of Exeter), Tony Sainsbury (Zoological Society of London), Helen Taylor (Royal Zoological Society for Scotland) and Alan Walker (Cefas). The Environment Agency has reviewed, provided inputs and made contributions to this report, particularly in relation to its organisational and regulatory remit. The following people from the Environment Agency have contributed to the review report through discussion and/or provision of advice, information and data for which Natural England is very grateful: Elly Andison, Sean Arnott, Lydia Burgess-Gamble, Chris Catling, Steve Garner, Richard Jeffries, Viviana Levy, Joe March, Pam Nolan, Graham Scholey, Sarah Jane Scott, Andrea Shaftoe, Jo Shanahan, Graeme Storey, Simon Toms, Cathy Turtle, Chris Uttley, Neville White, Katie Whitlock and Huw Williams. A review of the evidence on the interactions of beavers with the natural and human environment in relation to England 3 Executive Summary Context The European Beaver (Castor fiber) was once widespread across Europe and northern Asia. It became extinct in England around the 16th century due to overhunting for its meat and fur. Beavers are ecosystem engineers and, as a keystone species, are able to restore wetland ecosystems and produce a mosaic of diverse riparian habitats. A five-year licence was issued by Natural England in 2015 to legitimise the presence of beavers that had been living wild on the River Otter in Devon, England, enabling an authorised trial of a beaver reintroduction. In 2020 a decision was made by Ministers, following the conclusion and assessment of trial results, to permit those free-living beavers to remain and continue to expand their range naturally. This has resulted in widespread interest in reintroducing beavers to new areas of England. Scope The purpose of this review is to inform decisions relating to reintroducing beavers more widely in England. It does this by reviewing evidence, relevant to England, on the interactions of beavers with the natural and human environment alongside the guidelines for reintroductions and other conservation translocations published by the International Union for the Conservation of Nature. This review focuses on new evidence available since an earlier feasibility assessment published by Natural England in 2009 and the subsequent publication in 2015 of an extensive review carried out by Scottish Natural Heritage. The aim is to identify and assess key evidence across a range of natural and socio-economic factors relevant to decisions on further beaver releases in England. Key conclusions The key findings from each topic reviewed are summarised below. As stated in the scope, this review is restricted to recent evidence available since the 2015 review by Scottish Natural Heritage. Although our knowledge of beavers in a British context has improved since 2015, there remain uncertainties in relation to some potential positive and negative impacts. Before considering the evidence, it is important to recognise that how the reintroduction of a lost keystone species like the beaver is perceived or judged is highly dependent on the reference point used from which to measure the effects. The existing ecological baseline in many areas of England, reflects highly altered or degraded ecosystems and this is critical context when considering the potential influences of beavers on habitats and species. As beaver populations expand, the extent to which their impacts are considered positive or negative is dependant on management and habitat restoration objectives. For example, is impact judged by referring to the local habitats present at the time the beavers are reintroduced, or by reference to other objectives, such as relating to ecosystem restoration? Natural England Research Report NEER017 4 The role of beavers in the restoration of more naturally functioning ecosystems cannot be considered without reference to natural controls on beaver populations, which are critical in providing dynamic balance to ecosystems. Restoring natural population controls (or mimicking of those controls) on native species should be seen as an integral part of restoring natural ecosystems. Ecological requirements for restoring a beaver population Restoring the beaver as a widespread native wild mammal in England is ecologically feasible. Evidence collected from the trial reintroductions in Great Britain, carried out since the 2009 feasibility study, confirm there is sufficient suitable habitat in England to support this species at many locations, the climate is appropriate and there is an appropriate source of beavers to use to found the initial population. Interactions with habitats Running water Recent evidence published since the Scottish Review complements previous evidence demonstrating that beaver activity can enhance the natural functions of river systems, although the extent of influence is dependent on the natural characteristics of the watercourse and the nature and scale of existing habitat degradation. Key factors affecting the response of watercourses to beaver activity include stream power, gradient and the size of naturally vegetated riparian zones. There is potential for significant habitat restoration opportunities associated with the delivery of large woody material to the channel and beaver activity in riparian zones, helping to restore lost habitat dynamism and diversity. The scale of ecological change will be highly site-specific and dynamic, but where beaver activity is high there will be an overall shift in the balance of lentic and lotic character and associated biological assemblages, in line with natural functioning of river ecosystems, as long as beaver population levels are subject to population controls that also mimic natural systems. Standing water habitats and associated wetlands Recent evidence published since the Scottish Review is consistent with previous evidence demonstrating that beavers can help restore wetlands and promote biodiversity. Beaver-induced ponded and wetland habitats have the potential to enhance and restore natural processes in English catchments with a significant benefit to overall wetland function. There have been many changes to the water environment since beavers were widely present and while many of the effects of beaver will be beneficial, there will also be situations where landowner objectives will differ, and conflict may occur. A review of the evidence on the interactions of beavers with the natural and human environment in relation to England 5 Woodlands Evidence from research published since the Scottish Review is in accord with previous evidence demonstrating that beavers can affect tree species composition and age structure of wet woodlands and woodlands along riparian corridors with subsequent positive impacts for biodiversity. Beaver activity within riparian woodlands is likely to lead to greater structural complexity and, consequently, greater diversity of conditions within woodlands, particularly in terms of wetness. As a result, there would also be greater diversity in hydro-chemistry, light availability and openness. Overall, beavers can create more heterogeneous and