Wildlife and Wind Farms - Conflicts and Solutions: Offshore: Monitoring and Mitigation

Wildlife and Wind Farms, Conflicts and Solutions

Dedication

This work is dedicated to my family: my wife Eleanor, with whom I share a vision of a better future for our planet; my children Merlin & Phoenix who are still young enough to wonder, and Morgan & Rowan, who took their place in society as women somewhere along the way; and my Mum and Dad. My Mum was taken from us before these books were completed and is acutely missed.

Published by Pelagic Publishing

www.pelagicpublishing.com

PO Box 874, Exeter, EX3 9BR, UK

Wildlife and Wind Farms, Conflicts and Solutions

Volume 4 Offshore: Monitoring and Mitigation

ISBN 978-1-78427-131-2 (Pbk)

ISBN 978-1-78427-132-9 (ePub)

ISBN 978-1-78427-134-3 (PDF)

Copyright © 2019

This book should be cited as: Perrow, M.R. (ed) (2019) Wildlife and Wind Farms, Conflicts and Solutions. Volume 4 Offshore: Monitoring and Mitigation. Pelagic Publishing, Exeter, UK.

All rights reserved. No part of this document may be produced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without prior permission from the publisher. While every effort has been made in the preparation of this book to ensure the accuracy of the information presented, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Pelagic Publishing, its agents and distributors will be held liable for any damage or loss caused or alleged to be caused directly or indirectly by this book.

A catalogue record for this book is available from the British Library.

The data in this book belong to the authors and contributors of the corresponding chapters and any further analyses or publications should not be undertaken without the approval of the authors.

Colour reproduction of this book was made possible thanks to sponsorship by Vattenfall Wind Power Limited™. For more information visit https://corporate.vattenfall.com/

Cover images:

Top: Use of a double big bubble curtain in combination with a hydro-sound damper system around the pile during installation of one of the turbine foundations at Wikinger offshore wind farm in the Baltic Sea in 2016. (Hydrotechnik Lübeck GmbH)

Left: Radio-tagged Little Tern Sternula albifrons foraging at sea around Scroby Sands (UK); thought to be the first seabird species to be tagged in relation to wind-farm studies (2003–2006). (Martin Perrow)

Middle: A multi-sensor bird detection system combining radar technology (left) with a visual and thermal camera (right) as installed at Thanet offshore wind farm (UK) during the Offshore Renewables Joint Industry Programme Bird Collision Avoidance Study. (Thomas W Johansen)

Right: Image from an aerial survey of the seal haul-out on the main sandbank of Scroby Sands as part of the monitoring programme of the effects of the nearby Scroby Sands wind farm (UK) upon Harbour Seals Phoca vitulina and Grey Seals Halichoerus grypus. (Air Images Ltd)

Contents

Contributors

Preface

1Monitoring invertebrates and fish

Thomas G. Dahlgren, Linus Hammar and Olivia Langhamer

2Monitoring marine mammals

Meike Scheidat and Lindsay Porter

3Surveying seabirds

Andy Webb and Georg Nehls

4Telemetry and tracking of birds

Chris B. Thaxter and Martin R. Perrow

5Modelling collision risk and predicting population-level consequences

Aonghais S. C. P. Cook and Elizabeth A. Masden

6Measuring bird and bat collision and avoidance

Markus Molis, Reinhold Hill, Ommo Hüppop, Lothar Bach, Timothy Coppack, Steve Pelletier, Tobias Dittmann and Axel Schulz

7Mitigating the effects of noise

Frank Thomsen and Tobias Verfuß

8Mitigation for birds with implications for bats

Andrew J. P. Harwood and Martin R. Perrow

9Perspectives on marine spatial planning

Johann Köppel, Juliane Biehl, Marie Dahmen, Gesa Geissler and Michelle E. Portman

Index

Contributors

Sophy Allen Specialist Services and Programmes Team, Chief Scientist Directorate, Natural England, Ground Floor, Sterling House, Dix's Field, Exeter EX1 1QA, UK

Lothar Bach Freilandforschung, zoologische Gutachten, Hamfhofsweg 125 b, D-28357 Bremen, Germany

Richard J. Berridge ECON Ecological Consultancy Ltd, Unit 7 Octagon Business Park, Little Plumstead, Norwich NR13 5FH, UK

Juliane Biehl Berlin Institute of Technology (TU Berlin), Environmental Assessment & Planning Research Group, Sekr. EB 5, Straße des 17. Juni 145, D-10623 Berlin, Germany

Richard Caldow Birds Team – Specialist Services & Programmes, Natural England, W4, Dorset Council, County Hall, Colliton Park, Dorchester, Dorset DT1 1XJ, UK

Filipe Canário STRIX, Environment and Innovation, Rua Roberto Ivens 1314 esc. 1.14–15, 4450-251 Matosinhos, Portugal

Timothy Coppack APEM Ltd, Riverview, A17 Embankment Business Park, Heaton Mersey, Stockport SK4 3GN, UK

Aonghais S. C. P. Cook British Trust for Ornithology, The Nunnery, Thetford IP24 2PU, UK

Thomas G. Dahlgren NORCE, Postboks 22 Nygårdstangen, N-5838 Bergen, Norway and University of Gothenburg, Department of Marine Sciences, Box 461, SE 405 30 Gothenburg, Sweden

Marie Dahmen Berlin Institute of Technology (TU Berlin), Environmental Assessment & Planning Research Group, Sekr. EB 5, Straße des 17. Juni 145, D-10623 Berlin, Germany

Tobias Dittmann IfAÖ Institut für Angewandte Ökosystemforschung GmbH, Carl-Hopp-Str. 4a, D-18069 Rostock, Germany

Gesa Geissler Berlin Institute of Technology (TU Berlin), Environmental Assessment & Planning Research Group, Sekr. EB 5, Straße des 17. Juni 145, D-10623 Berlin, Germany

Larry Griffin Wildfowl & Wetlands Trust, Slimbridge, Gloucester GL2 7BT, UK

Linus Hammar Chalmers University of Technology, Department of Technology Management and Economics, Division of Environmental Systems Analysis, SE-412 96 Gothenburg, Sweden

Andrew J.P. Harwood ECON Ecological Consultancy Ltd, Unit 7 Octagon Business Park, Little Plumstead, Norwich NR13 5FH, UK

Stefan Heinänen DHI A/S, Agern Allé 5, DK-2970 Hørsholm, Denmark

Reinhold Hill Avitec Research, Sachsenring 11, D-27711 Osterholz-Scharmbeck, Germany

Baz Hughes Wildfowl & Wetlands Trust, Slimbridge, Gloucester GL2 7BT, UK

Ommo Hüppop Institute of Avian Research ‘Vogelwarte Helgoland’, An der Vogelwarte 21, D-26386 Wilhelmshaven, Germany

Sue King Sue King Consulting Ltd, The Coach House, Hampsfell Road, Grange-over-Sands LA11 6BG, UK

Johann Köppel Berlin Institute of Technology (TU Berlin), Environmental Assessment & Planning Research Group, Sekr. EB 5, Straße des 17. Juni 145, D-10623 Berlin, Germany

Olivia Langhamer Chalmers University of Technology, Department of Technology Management and Economics, Division of Environmental Systems Analysis, SE-412 96 Gothenburg, Sweden

Aulay Mackenzie Wrexham Glyndŵr University, Mold Road, Wrexham LL11 2AW, UK

Elizabeth A. Masden Environmental Research Institute, North Highland College-UHI, University of the Highlands and Islands, Ormlie Road, Thurso KW14 7EE, UK

Roel May Norwegian Institute for Nature Research (NINA), PO Box 5685 Sluppen, NO-7485, Trondheim, Norway

Sara Méndez-Roldán Niras Consulting Ltd, St Giles Court, 24 Castle Street, Cambridge CB3 0AJ, UK

Markus Molis Avitec Research, Sachsenring 11, D-27711 Osterholz-Scharmbeck, Germany

Georg Nehls BioConsult SH GmbH & Co. KG, Schobüller Str. 36, 25813 Husum, Germany

Tim Norman Niras Consulting Ltd, St Giles Court, 24 Castle Street, Cambridge CB3 0AJ, UK

Steve Pelletier Stantec Consulting Services, Inc., 30 Park Drive, Topsham, ME 04086, USA

Martin R. Perrow ECON Ecological Consultancy Ltd, Unit 7 Octagon Business Park, Little Plumstead, Norwich NR13 5FH, UK

Lindsay Porter SMRU Hong Kong, The University of St. Andrews, 17/F Tower 1, Lippo Centre, 89 Queensway, Hong Kong SAR

Michelle E. Portman Segoe Building 502, Faculty of Architecture & Town Planning, Technion-Israel Institute of Technology, Haifa 32000, Israel

Eileen Rees Wildfowl & Wetlands Trust, Slimbridge, Gloucester GL2 7BT, UK

Jan T. Reubens Flanders Marine Institute, Wandelaarkaai 7, 8400 Ostend, Belgium

Viola H. Ross-Smith British Trust for Ornithology, The Nunnery, Thetford, IP24 2PU, UK

Meike Scheidat Wageningen Marine Research, PO Box 68, 1970AB IJmuiden, The Netherlands

Axel Schulz IfAÖ Institut für Angewandte Ökosystemforschung GmbH, Carl-Hopp-Str. 4a, D-18069 Rostock, Germany

Eleanor R. Skeate ECON Ecological Consultancy Ltd, Unit 7 Octagon Business Park, Little Plumstead, Norwich NR13 5FH, UK

Henrik Skov DHI A/S, Agern Allé 5, DK-2970 Hørsholm, Denmark

Chris B. Thaxter British Trust for Ornithology, The Nunnery, Thetford, IP24 2PU, UK

Frank Thomsen DHI A/S, Agern Allé 5, DK-2970 Hørsholm, Denmark

Ricardo Tomé STRIX, Environment and Innovation, Rua Roberto Ivens 1314 esc. 1.14–15, 4450-251 Matosinhos, Portugal

Mark L. Tomlinson ECON Ecological Consultancy, Unit 7 Octagon Business Park, Little Plumstead, Norwich NR13 5FH, UK

Inge van der Knaap Marine Biology Research Group, Ghent University, Krijgslaan 281/S8, 9000 Ghent, Belgium

Tobias Verfuß The Carbon Trust, CBC House, 24 Canning Street, Edinburgh EH3 8EG, UK

Robin Ward Niras Consulting Ltd, St Giles Court, 24 Castle Street, Cambridge CB3 0AJ, UK

Andy Webb HiDef Aerial Surveying Ltd, Phoenix Court, Earl Street, Cleator Moor, Cumbria, CA25 5AU, UK

Preface

Wind farms are seen to be an essential component of global renewable energy policy and the action to limit the effects of climate change. There is, however, considerable concern over the effects of wind farms on wildlife, especially on birds on bats onshore, and seabirds and marine mammals offshore. On a positive note, there is increasing optimism and evidence that by operating as reefs and by limiting commercial fishing activity, offshore wind farms may become valuable in conservation terms, perhaps even as marine protected areas.

With respect to any negative effects, Environmental Impact Assessment (EIA) adopted in many countries should, in theory, reduce any impacts to an acceptable level, particularly as this should also incorporate any mitigation required. Although a wide range of monitoring and research studies have been undertaken, only a small body of that work appears to be represented in the peer-reviewed literature. The latter is burgeoning, however, concomitant with the interest in the interactions between wind energy and wildlife as expressed by the continuing Conference on Wind Energy and Wildlife Impacts (CWW) series of international conferences on the topic. A total of 342 participants from 29 countries attended CWW 2017 in Estoril, maintaining similar numbers on both counts to that achieved at CWW 2015 in Berlin. Let us hope that CWW 2019 in Stirling (Scotland) has a similar audience. Recent considerable interest within individual countries suggests this should be the case. For example, the Wind Energy and Wildlife seminar (Eolien et biodiversité) including both onshore and offshore wind, attracted over 400 participants to Artigues-près-Bordeaux, France on 21–22 November 2017.

Even with specific knowledge of the literature as well as participation in meetings, I reached the conclusion (some time ago now) that there was a clear need for a coherent overarching review of potential and actual effects of wind farms and, perhaps even more importantly, how impacts could be successfully avoided or mitigated. Understanding the tools available to conduct meaningful research is also clearly fundamental to any research undertaken. A meeting with Nigel Massen of Pelagic Publishing in late 2012 at the Chartered Institute of Ecology & Environmental Management Renewable Energy and Biodiversity Impacts conference in Cardiff, UK crystallised the notion of a current treatise and the opportunity to bring it to reality. Even then, the project could not have been undertaken without the significant financial support of ECON Ecological Consultancy Ltd. expressed as my time.

At the outset of the project I did not imagine the original concept (one volume for each of the onshore and offshore disciplines) would morph into a four-volume series; with onshore and offshore each having a volume dedicated to (i) documenting current knowledge of the effects – the conflicts with wildlife; and (ii) providing a state-of-the-science guide to the available tools for monitoring and assessment and the means of avoiding, minimising and mitigating potential impacts – the solutions. I also did not imagine that the gestation time to produce the volumes would be nearly seven years, or that the offshore volumes would run two years behind the onshore volumes. The offshore industry has developed rapidly in the last few years and this meant many potential authors were swamped by their workloads within various roles within the industry. Perhaps inevitably, several authors fell by the wayside, which caused delays and some stop and start in the process as replacements were found. However, I believe this has meant that the books have ultimately benefited by being able to document the rapid progress that has occurred in the last few years and by having a particularly active team of authors at the top of their game.

In this Volume 4, documenting monitoring and mitigation as the solutions to any conflicts offshore, the concept was to cover the main groups that have been the focus of monitoring efforts, namely birds, especially seabirds, marine mammals, fish and invertebrate communities. As relatively little work has yet to be conducted on fish, these are included with invertebrates in the opening chapter Monitoring invertebrates and fish, before subsequent chapters on Monitoring marine mammals and Surveying seabirds. Both the Monitoring invertebrates and fish and Monitoring marine mammals chapters include information on telemetry, with the latter perhaps providing the most relevant information on any telemetry of mega-fish such as sharks, or even sea turtles required in future wind-farm studies. Such has been the rapid advance in, and popularity of, the application of telemetry in relation to birds, including both seabirds and migrant terrestrial species such as waterfowl; a separate chapter on Telemetry and tracking of birds is warranted. This concludes the monitoring section of the volume, before a switch in focus to Modelling collision risk and predicting population-level consequences. The recent work offshore expands that conducted onshore and documented in Volume 2 of this series, notably in trying to tackle the greater degree of ‘unknowns’ offshore, where the rate of collision cannot be confirmed through carcass collection, as it may be onshore. This has stimulated the technological advance of remote methods to detect collisions in the challenging conditions at sea that are thoroughly reviewed in Measuring bird and bat collision and avoidance, and that provides the means of populating the collision risk models covered in the previous chapter. The chapter also includes exciting work on the telemetry of small migratory birds such as passerines, that have similar traits to bats, to complement the earlier Telemetry and tracking of birds chapter.

The volume then moves into mitigation, beginning with Mitigating the effects of noise that reviews all current technological options in reducing construction noise in particular, especially where this is undertaken with pile-driving, which is widely thought to be one of the principal threats of offshore wind-farm development to wildlife such as marine mammals and fish. Mirroring the mitigation hierarchy approach adopted in the equivalent onshore chapter in Volume 2, Mitigation for birds outlines some of the mostly theoretical options for reducing collision and displacement of birds, several of which also stem from research onshore. The subtitle ‘with implications for bats’ nods to some of the additional information provided in a stand-alone box. The final chapter of the nine, Perspectives on marine spatial planning, provides a history of how plans to install offshore wind farms have been a key driver of marine spatial planning and provides a series of recommendations in relation to future planning requirements that are a crucial first step in avoiding potential impacts of wind farms.

To promote coherence within and across volumes, a consistent style was adopted for all chapters, with seven sub-headings: Summary, Introduction, Scope, Themes, Concluding remarks, Acknowledgements and References. For ease of reference, the latter are reproduced after each chapter. The carefully selected sub-headings break from standard academic structure (i.e. some derivative of Abstract, Introduction, Methods, Results and Conclusions) in order to provide flexibility for the range of chapters over all four volumes, many of which are reviews of information, whilst others provide more prescriptive recommendations or even original research. Some sub-headings require a little explanation. For example, the Summary provides an up to ~300-word overview of the entire chapter, whilst the Concluding remarks provide both conclusions and any recommendations in a section of generally ~500 words. The Scope sets the objectives of the chapter, and for the benefit of the reader describes what is, and what is not, included. Any methods are also incorporated therein. The Themes provide the main body of the text, and are generally divided into as few sub-heading levels as possible. Division of material between wind-farm phases (e.g. construction, operation and decommissioning) was generally avoided as this increased the number of sub-headings and led to an unwieldy structure. Rather, any clear differences between wind-farm phases, for example where specific monitoring methods should be applied, were incorporated into specific sub-headings.

As well as being liberally decorated with tables, figures and especially photographs, which are reproduced in colour courtesy of sponsorship by Vattenfall, most chapters also contain Boxes. These were designed to be provide important examples of a particular point or case or suffice as an all-round exemplar; and thus ‘stand-alone’ from the text. In a few cases, these have been written by an invited author(s) on the principle that it is better to see the words from the hands of those involved rather than paraphrase published studies. My sincere thanks go to all 26 chapter authors and further 21 box authors (excluding myself in both cases) for their contributions. I take any deficiencies in the scope and content in this and its sister volume to be my responsibility, particularly as both closely align to my original vision, and many authors have patiently tolerated and incorporated my sometimes extensive editorial changes to initial outlines and draft manuscripts.

Finally, it needs to be stated that with a current epicentre in northwestern Europe in the North and Baltic Seas, the coverage of this book could not exactly be global. However, as the offshore wind industry develops at almost breakneck speed in a great range of countries, I hope the information and experiences gleaned from the pages of this book can be applied in a global context; with the proviso that applying any lessons learned to marine systems elsewhere on the planet would need to be accompanied by specific research to account for any inevitable differences in ecological structure and functioning of those systems. Hopefully, this book is a further step towards the sustainable development of wind farms and the ultimate goal of a win–win1 scenario for renewable energy and wildlife.

Martin R. Perrow

ECON Ecological Consultancy Ltd.

21 June 2019

1Kiesecker, J.M., Evans, J.S., Fargione, J., Doherty, K., Foresman, K.R., Kunz, T.H., Naugle, D., Nibbelink, N.P. & Niemuth, N.D. (2011) Win–win for wind and wildlife: a vision to facilitate sustainable development. PLoS ONE 6: e17566.

CHAPTER 1

Monitoring invertebrates and fish

THOMAS G. DAHLGREN, LINUS HAMMAR and OLIVIA LANGHAMER

Summary

Current knowledge is often sufficient to predict and prevent degradation of ecosystems, through careful planning, technology choice, good practice, and mitigation and restoration measures. Baseline studies and environmental monitoring programmes must be carefully planned and employ rigorous data collection if the analyses are to be capable of showing significant results for both anticipated and unforeseen effects. Since baseline studies of wind farms are performed at a fine scale, monitoring data may also serve as fundamental research on faunal distribution and behaviour, as well as playing a crucial role in the consenting and permitting processes. The continuously growing offshore wind industry requires certainty about effects before, during and after installation, to minimise or even eliminate any potential detrimental impacts on marine habitats and ecosystems. This chapter reviews monitoring methods, technologies and scientific tools that are commonly applied to monitoring fish and invertebrates at operational sites. Seabed communities are defined as the interacting assemblage of organisms in the sediment (infauna) and on sediment and structures (epifauna and algae), as well as demersal and pelagic fish. Case studies from scientifically developed monitoring programmes and studies are provided as examples of rigorous data gathering capable of showing environmental change. A successful baseline study and monitoring programme is likely to include a combination of traditional tools, such as fyke-net fishing, and modern and developing technologies, such as sonar and the use of telemetry to track the response of individual fish to wind-farm construction and operation. To further our understanding of long-term and cumulative impacts, data from monitoring programmes should ideally be collected, analysed and reported in a way that allows for future additional analyses. Examples of such data include changes in benthic community structure that may affect shelf ecosystem services such as carbon mineralisation and/or burial, or changes in fish diversity and abundance.

Introduction

Environmental issues play a central role in the consenting process of offshore wind projects. As evidenced by Volume 3 in this series (Perrow 2019), the already substantial volume of science-based information on the environmental impact of offshore wind farms (OWFs) is still growing, most importantly with regard to long-term and cumulative impacts. In combination with an increasingly comprehensive palette of strategies to avoid short-term impact and long-term degradation of ecosystems, the arguments to stop a wind farm based on the precautionary principle alone are becoming weaker. After more than 15 years of environmental monitoring surveys and scientific research at OWFs, much has been learned regarding the effects on marine ecosystems. The strongest and best understood environmental stressors are associated with the construction phase, although the operational phase likely affects oceanographic processes (Broström et al. 2019) and the distribution and abundance of animals and therefore ecosystem functioning (Perrow 2019). In comparison to wind power on land, the use of large turbines in OWFs is facilitated by a combination of low landscape impact, eased logistics as a result of ship-borne transport and assembly of turbines, and remote operation and maintenance. However, OWFs are relatively sparsely packed, sometimes with 1 km or more between turbines. Hence, the direct areal impact on marine habitats is very minor in relation to installed capacity. Typically, the foundation footprint, and thus the habitat required to be offset, is small compared to the total occupied area. Nevertheless, physical habitat change is one of the most evident environmental issues for seabed communities, comprising the interacting assemblage of organisms in the sediment (infauna) and on sediment and structures (epifauna and algae), and benthic fish (Dannheim et al. 2019). Foundations, scour protection and cable trenches typically induce habitat change, expressed as both introductions of new ‘hard-surface’ and intertidal habitats (habitat gain), and loss of habitats, such as particular sediments due to extraction, burial or changed granulometry caused by altered current patterns.

Introduction of large structures in the sea causes a potentially beneficial ‘reef effect’, which contributes towards increased biodiversity by attracting both filter-feeding epifauna and larger mobile scavengers, such as crabs and benthic fish (Dannheim et al. 2019). Demersal and benthopelagic fish use the structures as fish-aggregation devices, attracted by biofouling organisms (Stenberg et al. 2015; Gill & Wilhelmsson 2019). The species involved include large predators, such as Atlantic Cod Gadus morhua (Reubens et al. 2013; 2014a; 2014b). Top predators, including marine mammals (Nehls et al. 2019), especially seals (Russell et al. 2014), and some seabirds, such as Great Cormorant Phalacrocorax carbo and Great Black-backed Gull Larus marinus (Vanermen & Stienen 2019), may also be attracted, resulting in a more patchy distribution of these groups. An additional effect of the increased availability of hard structures is a significant increase in filter-feeding bivalves (Mytilus spp.), with the potential to alter the area’s benthic productivity rate and water clearance (Krone et al. 2013). Altogether, redistribution of marine organisms potentially changes ecosystem functions and predator–prey dynamics, affecting sediment-dwelling, pelagic and sessile organisms. The introduction of new habitat types allows for the colonisation of new, possibly invasive, species that benefit from artificial structures in open water. As OWFs are often sited far from a natural shore, the artificial intertidal habitat can potentially be used as a stepping stone for splash-zone and shallow-water dependent propagules that would otherwise perish in open water. One example is the Pacific Oyster Crassostrea gigas (Gutow et al. 2014; de Mesel et al. 2015).

During construction, dredging and trenching also cause short-term increased turbidity that can harm both filter-feeding organisms (Rosenberg 1977) and fish eggs and larvae (Westerberg et al. 1996). However, in most circumstances the sediment spill from construction works causes high particle concentrations only over a very localised area, often not exceeding naturally occurring levels farther than 100 m from the source (Bergström et al. 2012). Other pollutants that may cause harm to the environment include the fuels and lubricants that could be accidentally spilled from the vessels present throughout the life of the wind farm, but especially in the construction phase (Rees & Judd 2019). Similarly, the cooling agents and lubricants needed for wind-turbine transmission gear and generators within an operational wind farm may be harmful even if released in very small quantities. A more site-specific problem is the possible release of old pollutants previously dumped or accumulated in the sediment, if these are suspended during cable trenching or seabed preparation (e.g. gravity foundations require dredging). This specific risk of secondary exposure due to the potential release of toxic sediment was a reason for halting the planning of a wind-power project prospected by Vindplats Göteborg in 2014, at an old dredge dump site in the mouth of the Göta älv River on the Swedish west coast.

Electromagnetism is emitted from cables within the wind farm and, to a larger extent, from power cables connecting with land. The electric component of the electromagnetic field (EMF) produced is effectively shielded by cable armour, but the magnetic component persists and, in turn, gives rise to a secondary induced electric field. Elasmobranchs use electric fields to detect prey buried in the sediment and can therefore be disturbed by cables of the kind used in wind farms (Gill 2005; Gill & Wilhelmsson 2019). It has also been shown that migrating fish, such as eels, can be disturbed by strong magnetic fields, slightly diverting them from their track (Westerberg & Lagenfelt 2008). To date, field experiments conducted at wind farms have not been able to show any significant effects on either benthos or fish, but it is reasonable to believe that wind-power cables with strong EMFs can have some level of effect on sensitive animals (Lagenfelt et al. 2012).

In contrast, in theory, the noise and vibration energies from pile driving are a more severe threat to the ecosystem at least in the short-term. Pile driving is required to install the more common monopole turbine designs as well as the pin piles associated with jacket and tripod designs (Jameson et al. 2019). The assumed acute effects on fish caused by pile-driving noise during construction include behavioural changes, such as escape, avoidance, relocation and change of community structure. The physiological effects include acute tissue or barotrauma damage induced by seismic pressure waves to animals with air-filled cavities, often followed by low survival rates (Nedwell et al. 2003a; Müller 2007; Popper & Hastings 2009; Bailey et al. 2010). During operation of a wind farm, noise emissions are low, but they increase with turbine and wind-farm size (Nedwell et al. 2003a). It has been shown that some fish species can be stressed by operational noise as a low-intensity stressor (Engås et al. 1995; Kastelein et al. 2008; Caiger et al. 2012) by having, for example, an increased respiration rate (Wikström & Granmo 2008). Continuous noise has also been shown to impair reproductive success in Atlantic Cod (Sierra-Flores et al. 2015). Still, habituation can occur when fish are continuously exposed to noise levels comparable to those in harbours and areas of intense shipping activity. Indirect effects of noise on fish include the masking of natural sounds or bioacoustics (Wahlberg & Westerberg 2005; Simpson et al. 2015). In many fish species, the use of sound is common for finding prey, avoiding predators, interspecies communication, finding a mate, and even for orientation and navigation. Noise has also been shown to act as a settling cue for fish and decapod species (Montgomery et al. 2006). Consequently, species abundance and community dynamics can be affected negatively in operational wind farms. Elasmobranchs, for example, have well-developed ears and sound plays an important role in their lives, although there are as yet no studies on the impact of OWF construction and operational noise on elasmobranchs.

To date, noise effects on marine invertebrates have also not been studied. However, the response to noise in invertebrates is rather species-specific and cannot be generalised. Crustaceans, such as shrimps, krills, crabs and lobsters, respond with a high variation in behaviour, feeding rate, growth, reproduction, metabolic level and mortality (Lagardère 1982; Carroll et al. 2017). Hitherto, detrimental effects of turbine noise have been shown only under laboratory conditions, while no corresponding effects have been detected in monitoring at actual wind farms.

A range of relatively general actions may be taken to mitigate the effects of operation and especially construction of OWFs on invertebrates and fish detailed below (Box 1.1). Fish, in particular, potentially benefit greatly from the mitigation of pile-driving noise typically directed at marine mammals, such as the use of bubble curtains and casings, as well as adjustment of piling energy, pulse prolongation and advances in piling technology (see Thomsen & Verfuß, Chapter 7). Irrespective of whether mitigation is attempted, wind-farm projects are typically obliged to involve environmental monitoring programmes. The purposes of monitoring include verification that any effect was indeed within acceptable impact boundaries, with or without mitigation, and detecting any unforeseen environmental impacts. Such monitoring also contributes to the general understanding of how OWFs affect the local and regional environment. A properly designed baseline study and monitoring programme may also be used to test the validity of future suggestions or even accusations that the wind farm had a role in any observed ecological degradation, when other stressors, such as climate change or increased shipping activities, could have been the cause. Hence, it is of crucial importance that monitoring programmes use appropriate methods and are based on a rigorous statistical framework accounting for site-specific spatial and temporal physical and biological variations.

Box 1.1 Avoiding and mitigating wind-farm impacts upon invertebrates and fish

Here, best practice to avoid and mitigate the impact of wind farms, during siting, construction, operation and decommissioning, upon infaunal, epifaunal and demersal and pelagic fish assemblages is described following a traditional mitigation hierarchy of avoid, reduce, compensate and restore (Cuperus et al. 1996; 1999; Vaissière et al. 2015). The mitigation of noise impacts is described in more detail by Thomsen & Verfuß (Chapter 7).

Siting

Considerations over the siting of wind farms and turbines to reduce any effects on seabed integrity and vulnerable species and habitats will help to avoid an overall impact on the ecosystem. The micro-siting of individual turbines within a wind farm may minimise any impact on more valuable habitats in a patchy mosaic, such as seagrass (Zostera) meadows, mussel banks, or patches of coarse sand and gravel in an otherwise silty area. Micro-siting should also be considered to avoid the need for dredging in a heterogeneous seabed with alternating soft and hard substrates and to avoid patches of contaminants on the seabed.

The macro-siting of the entire wind farm will inevitably be subject to a large number of factors, of which avoiding potential habitat degradation is only one. Such macro-siting considerations include avoiding unique vulnerable environments or areas that maintain sensitive and important ecological functions, such as particular fish spawning sites and wintering sites for seabirds. The avoidance of specific sites can also be considered in order to minimise the risk of their acting as stepping stones for invasive species. Siting considerations must, however, be based on well-documented anticipated impact in a risk-analysis framework, otherwise there is a risk that various avoidance arguments are used as a pretext to protect unrelated interests. In addition, siting of a project in a disturbed area can be preferable to a development in a pristine environment (Inger et al. 2009). The reason for this is two-fold. First, already degraded environments typically represent a benthic community that is more resilient to disturbance compared to pristine environments. Secondly, positive effects of wind farms, such as exclusion of fishing and increased diversity and productivity due to the reef effect, are likely to be more valuable in a degraded ecosystem. An offshore wind farm may actually help to improve the ecological status in a previously degraded environment (Bergström et al. 2014).

Wind-farm design

The technical design of a wind farm has an influence on how individual turbine foundations are positioned in relation to benthic habitats. If turbines are located in seagrass beds, mussel beds or other biotopes of particular ecological value, the benthic footprint will be more detrimental than if turbines are positioned on less vulnerable biotopes, such as mud and sand bottoms. It is, however, generally difficult to determine the exact positioning of turbines in a wind farm at the consent stage as a result of the rapid technological development of the type and size of foundations and turbines. Wind farms are therefore often planned according to the ‘box model’, meaning that the outer borders of the wind farm are determined and the design of the wind farm inside this ‘box’ is only indicated according to a ‘design envelope’. In cases where vulnerable or particularly valuable biotopes are present inside the wind-farm area, it can be difficult to ensure that these sites are avoided during the final design. A suggested solution to this is that the consenting authorities apply legal conditions, stating that the final positioning of foundations and cable trenches must avoid ecologically valuable sites during the micro-siting phase.

The design of a wind farm may also influence how hydrodynamics are affected, with a relatively dense wind farm having more potential impact than a more sparsely designed wind farm with a lot of space between turbines. Moreover, it has been postulated that a wind farm that captures a large portion of the incoming wind may induce an artificial upwelling in the wake caused on the lee side (Broström 2008), and field evidence supporting this theory has been gathered (Broström et al. 2019).

Timing

Timing of construction events can be an important element of risk mitigation (Bergström et al. 2012; Hammar et al. 2012). It is well known that pile driving generates hazardous high-intensity sound and that dredging under certain conditions can cause locally harmful levels of dissolved particles. Seasonal events to avoid such impacts are typically related to ecological functions such as reproduction and migration. Regarding the benthic community, the importance of such time-dependent considerations is more relevant for fish than for invertebrates (Bergström et al. 2012). In one case, the construction of a wind farm during the spawning period of a local population of Atlantic Herring Clupea harengus was thought to be responsible for a significant reduction in the strength of recruitment, with a significant knock-on effect on the feeding conditions of a breeding seabird, the Little Tern Sternula albifrons, at what was then its most important colony in the UK (Perrow et al. 2011).

In Sweden, it is common practice to allow potentially harmful construction events only within a limited time window. This applies both to offshore wind power and to other activities consented under the Swedish Environmental Code. For large projects, narrow time windows for construction can increase construction time considerably, especially when combined with windows of favourable weather. The question of time restrictions during the construction phase is a balance between shorter, intense disturbance and prolonged but lower disturbance. Piling and dredging at a single foundation take hours and days, respectively. A large wind farm with hundreds of turbines may thus take years to construct, even without time restrictions. Long-term disturbance is typically considered more significant than short-term disturbance because a more inclusive part of the population will be exposed and since no time will be given for recovery. Yet such temporally prolonged disturbance can have little ecological impact if important functions are not affected (Hammar et al. 2014). If the wind farm is large enough, the construction activity can be alternated between opposing sites within the area, relieving the benthic community on one side of the farm at a time.

Mitigation through technology choice

Other than siting and timing, discussed above, the material, type and design of the foundations are important features that can be optimised in an environmental sense based on general and local circumstances. For instance, there is a range of foundation types that minimise the use of heavy piling. In areas sensitive to piling noise, consideration should be given to avoiding the use of monopile foundations (heavy piling) and instead relying on gravity foundations, drilled foundations or foundations based on small-diameter piles (Hammar et al. 2008), although these are more expensive.

Compared to steel foundations, concrete-based gravity foundations trigger fouling organisms to settle at a significantly higher rate (Degraer 2012) and also emit less turbine vibration during operation (Hammar et al. 2008). However, concrete foundations have the disadvantage of being significantly more expensive than steel.

Jacket foundations have complex structures that enhance the reef effect and generate weaker vibrations than monopile foundations, albeit more than gravity foundations. Therefore, the foundation type, material and coating can be specifically chosen to influence the levels of settling larvae, the extent of the reef effect and the level of noise (vibration) disturbance (Table 1.1). In general, monopile foundations emit most noise but have least impact on the seabed community in terms of fouling, reef effect and space occupation. Conversely, gravity foundations and jacket foundations emit lower noise but impose a higher change on the benthic community.

Table 1.1 Relative magnitudes of effects on seabed communities from different types of foundations (note that all effects are not necessarily negative at all sites

It should be noted that, regarding the effects of vibrations and noise, only limited data are available, covering only a small range of turbine and foundation types. More research and monitoring are needed to understand how particular types of tower, turbine, gear and generator design affect the level of noise transmitted into the water. Earlier types of tower-to-foundation connectors (grouting) have been replaced with heavy rubber pads that more effectively absorb vibrations. While this is done to prolong the lifetime of the turbine, it has the additional benefit of reducing the noise energy transmitted from the nacelle to the foundation and surrounding water.

As the offshore wind industry develops and occupies more space in the ocean, it becomes increasingly important to implement technical adjustments in order to minimise stressors that generate subtle effects, such as underwater noise, so that long-term ecological effects are prohibited (Slabbekoorn et al. 2010). Underwater noise is included among the 11 descriptors for good environmental status in the European Union Marine Strategy Framework Directive (EU 2008), and as such, should be limited.

Compensation and restoration

Compensation to stakeholders to offset the impacts on ecosystem services may include a range of measures (Elliott et al. 2014). A paper based on data collected from a French project organises ecosystem services into three categories: (a) provisioning, (b) regulating and (c) cultural (which is not within the scope of this chapter) (Kermagoret et al. 2014). For provisioning ecosystem services (a), two major impacts were perceived from stakeholders: loss of fishing opportunities and gain of clean energy. The loss of fishing opportunities is expected from the restriction in exploitable area and the disturbance during the development phase. However, there are examples in the UK where lucrative pot fisheries for European Lobster Homarus gammarus and Edible Crab Cancer pagurus have developed as a result of the presence of wind-farm structures. Some comments from stakeholders highlighted the potential for increased production of offspring within the wind farm, which effectively acts as a marine protected area (Dannheim et al. 2019). This may increase the future catch per effort outside the wind farm (Bergström et al. 2014). As a compensation for the loss of fishing opportunity, a seeding programme of the most important catch, Great Scallop Pecten maximus, was agreed in the French project. In this case study, fisheries were also to be compensated by receiving 35% of the annual tax based on the electricity production that the project will pay the community (€14,000 per MW and year). The money was to be used to fund projects promoting sustainable fisheries and is thus the most important perceived impact on regulatory ecosystem service (b), coupled with a contribution to global climate regulation, which is inherent in all wind-farm projects. At a local scale, a reef effect was to be expected at each turbine foundation, which is positive in some respects (higher diversity and higher productivity), although the net impact was not possible to judge and no further compensation was suggested.

Irrespective of foundation type, the footprint of a turbine removes one type of habitat and replaces it with another. To compensate, a concrete gravity foundation can be cast in order to enhance the surface shape to maximise the availability of habitats for decapods such as crabs and lobsters, for example (Langhamer & Wilhelmsson 2009). In cases where a specific habitat, such as Zostera meadows, has been replaced or damaged, compensatory introduction of new Zostera meadows could be undertaken in a suitable area nearby.

Scope

This chapter is based on both monitoring reports and peer-reviewed scientific literature, with the intention of reviewing and outlining the status and applications of several different monitoring methods, focusing on fish and marine invertebrates. The main contributions are reported from the regulatory and science-driven environmental monitoring programmes in north-west European waters, including Belgium (Degraer 2012), the Netherlands (Lindeboom et al. 2011; 2015), Sweden (Bergström et al. 2013a, 2013b), Denmark (Stenberg et al. 2011), Germany (BSH & BMU 2014) and the UK (Huddleston 2010; MMO 2014). These countries have the longest experience in environmental impact assessments and monitoring of offshore wind-power installations. Academic research on ecological and environmental effects related to offshore wind power has so far mostly been carried out by Denmark, Germany, the UK and Sweden. Nevertheless, this research reflects the state of the art for wind-power monitoring in general and includes theoretical considerations for offshore wind development in developing markets in other parts of the world, such as the USA and Japan (Jameson et al. 2019).

Unfortunately, many of the monitoring programmes developed at existing OWFs have not been planned adequately. Some surveys may be limited in the development of survey methods while others may have focused on single-species systems. In a review of monitoring programmes for offshore wind projects in Europe, only 33% of the programmes had conducted a power analysis and in only 10% was the study based on a random sampling design (Enhus et al. 2017). Therefore, they may not have been able to deliver results as valuable as was intended, such as on effects on marine communities and/or ecosystems, or data that can be used in a wider context (MMO 2014). Nevertheless, there have been many studies on many different species and possible wind-farm induced stressors in the Baltic and North Sea region (reviewed in Bergström et al. 2014). The accumulated understanding of the main environmental impacts on fish and marine invertebrates, including the benthic communities, is substantial, although not yet entirely satisfactory with respect to long-term ecological effects (Dannheim et al. 2019; Gill & Wilhelmsson 2019).

Thus, it remains critical to carefully design wind-farm studies, and this forms the first theme of this chapter. This touches on the principles of what and when to sample, which is also covered to some extent in Box 1.1 in relation to avoiding impacts. The rest of the themes are focused on monitoring the different parts of the faunal assemblage, partly according to their location and including infauna, bottom coverage, epifouling of turbine bases and scour protection, benthic and demersal fish, and benthopelagic and pelagic fish. The basis of monitoring ecosystem functioning is then considered before the Concluding remarks, which are particularly focused on future studies.

Themes

Study design

To promote the sustainable development of offshore wind power as a primary source of renewable energy, it is essential to assess its effects and impacts. The study design is of great importance to be able to detect changes that can be related to wind farms. Taking a sufficient (depending on variation) number of samples and applying a before–after control-impact (BACI) design are two fundamental ways of strengthening a monitoring programme (Underwood 1994). Baseline studies typically have to be initiated 2–3 years before construction works begin to allow for sampling of temporal variation in biological parameters, including species’ composition, populations, biomass and coverage.

The major problem for monitoring programmes is the frequent, if not constant, lack of sufficient statistical power. This can lead to serious consequences, since a potential negative impact may continue without being detected. Statistical power describes how well a conducted study covers the risk of not detecting an actual effect (change) due to having too few replicates. In biological and ecological science, it is standard to consider P=0.05 as the threshold for significant results. This means that it has to be at least 95% certain that an effect indicated in a study reflects an actual effect. Since biological data are variable in nature and many marine organisms are particularly variable in abundance, many replicates are typically needed to detect an effect. If there is an effect that is smaller than can be detected by the number of sampled replicates, due to natural variation, the conclusion of the study will still be that no effect was found. Wrongly, this conclusion is often interpreted as there was no effect. In order to draw the conclusion that effects are not likely, the statistical power needs to be high. Typically, the statistical power should be 0.8 for a significant change, meaning that the study has an 80% chance of detecting an effect size of interest (typically 25–50% change) (Antcliffe 1999). The consequence of the low statistical power in many monitoring programmes is that even if many topics have been studied and few effects have been established, it is not possible to conclude that the studies demonstrate a lack of effect. The possible effects may just be smaller than the applied monitoring efforts are designed to detect. The statistical power may, in some cases, not be presented in the monitoring reports, but it appears likely that only a few of the hitherto presented monitoring studies on the effects of wind power on benthic communities have a statistical power close to the conventional level of 0.8 (Lindeboom et al. 2011; Enhus et al. 2017). To move the field forward and make statistically rigorous conclusions on non-significant effects, monitoring programmes should focus on a few questions and perhaps key indicator species that are likely to be sensitive to change (Box 1.2), and apply a high sampling rate to resolve them with high statistical power. An example of high statistical power, but showing no significant effect, can be found in the quantitative experiment of Langhamer et al. (2016), capturing, marking and recapturing Common Shore Crab Carcinus maenas at the Lillgrund OWF. About 4,000 crabs were marked and monitored, but a very low recapture rate was observed. Furthermore, no wind-farm effects, either positive or negative, could be shown on the distribution of sex or colour morphs or body condition of the crabs, in comparison to nearby reference areas.

An optimal experimental design would be to monitor the same species over a longer period and to conduct comparable experiments in other OWFs to observe the effects of time and locality, especially when there is a large time and spatial variation.

When selecting among sampling methods, it is important to strive for minimising variation in data and to make sure that the method is feasible for quantitative data collection under harsh offshore conditions. A good example of targeted methodology is provided by the study on Viviparous Eelpout Zoarces viviparus at Lillgrund OWF (Box 1.2).

Box 1.2 Monitoring Viviparous Eelpout Zoarces viviparus, a key indicator of change, at Lillgrund offshore wind farm in Sweden

About 4 years after the installation of the Lillgrund offshore wind farm (OWF) in Sweden (Figure 1.1), a study on local populations of Viviparous Eelpout Zoarces viviparus was initiated, comparing them with a similar reference site (Langhamer et al. 2018). Eelpout is a benthic rather stationary species that has been used as a key indicator organism in the Baltic and North Seas for monitoring anthropogenic effects. Since the fish is an ovoviviparous species, reproductive success and fry development can be linked to each individual pregnant female, including their health status (Figure 1.2). During field sessions in autumn 2011 and 2012, Viviparous Eelpout was captured with two or three linked and baited double fyke nets at ten randomised locations in the Lillgrund OWF, and at a natural reference site 8 km south of Lillgrund, deployed from a small fishing vessel (Figure 1.3). Thus, fyke nets were set at 40–60 stations on one day and collected and emptied on the next day.

Figure 1.1 Lillgrund offshore wind farm in the Baltic Strait, Sweden, established in 2007 and consisting of 48 turbines. (Thomas Dahlgren)

Figure 1.2 Size and condition status analysis of fry of the Viviparous Eelpout Zoarces viviparus. (Olivia Langhamer)

Figure 1.3 Small fishing vessel set up for Viviparous Eelpout Zoarces viviparus survey fishing using fyke nets. Note the tank on the port side for live transport of captured fish. (Thomas Dahlgren)

In all, 50 and 17 females were captured in 2011 and 2012, respectively. Biometrics, condition and reproductive success