Current state of knowledge of effects of offshore renewable energy generation devices on marine mammals and research requirements

2 Introduction

The expansion of offshore wind energy projects and the development of new technologies and devices for marine renewable energy (Wave and Tidal) generation and their imminent and potentially rapid deployment in Scottish waters mean that there is an urgent need to identify and fill certain crucial data gaps. The UK is committed to a massive increase in renewable energy generation over the next 20 years and wind, wave and tidal power will play a major role in meeting these targets. A key concern in the development of such industries is that there should be a realistic assessment of the net environmental impact of any developments. There are clear benefits in terms of low carbon energy generation and the socio-economic benefits of developing a major offshore industry. However, these must be weighed against a set of potential environmental impacts, including effects on marine mammals.

From an industry perspective, there are problems associated with planning and investment when operating in high energy marine environments. There are engineering and environmental risks that may be predicted and to some extent accounted for but there is a level of uncertainty associated with each of these risks and that uncertainty translates into increased regulatory constraint and increased cost.

From an environmental perspective, it is essential that potential effects are identified, and where possible quantified, to allow a realistic impact assessment to take place. Methods and strategies for avoiding the preventable consequences are needed, and mitigation strategies and methods are needed to minimise the impacts of residual effects.

Uncertainty about the scope and magnitude of such environmental risks means that regulators and advisors will adopt a precautionary approach. Reducing uncertainty will therefore allow more appropriate and proportional regulation of the marine renewable industry. This is to the advantage of regulators, industry and the environment.

2.1 Terminology

We use the phrase offshore renewable energy generation ( OREG) to cover all forms and stages of offshore energy generation. For the purposes of this review, OREG will be restricted to the three main generation methods of relevance to Scotland

• Wind-OREG: Offshore turbines that harvest wind energy
• Wave-OREG: Surface or near-surface devices that harvest wave energy
• Tidal-OREG: Underwater devices that harvest tidal current energy

The latter two types can be grouped as wet-OREG. We recognise that OREG transitions through a series of stages: survey, construction, operation and decommissioning.

OREG devices may have a range of effects on their local environment such as increased noise during construction or operation, increased risk of collision and injury or barrier effects due to physical obstruction. We refer to any such effects resulting from OREG developments as stressors. Whilst these are usually associated with a negative effect, there may be positive effects ( e.g. the reef effect). We refer to marine mammals as receptors. The impact of a stressor on an individual receptor may be physical ( e.g. collision trauma), physiological ( e.g. elevated hearing threshold), or behavioural ( e.g. move away from stressor). The relationship between the magnitude of the stressor and the resulting impact is termed the dose-response function.

2.2 Scope

The aims of this report were determined within the Marine Mammal Scientific Support Research Programme MMSS/001/11. Under this programme, the Sea Mammal Research Unit ( SMRU) was commissioned to undertake a series of tasks relating to the scientific background for good environmental management of the development of the offshore renewable industry in Scotland.

This report combines two of these commissioned tasks:

• MR1: Report on the current state of knowledge of effects of offshore renewable energy generators on marine mammals.
• MR2: Identify and prioritise research gaps relating to the findings of task MR1.

The details of these Task descriptions, taken from the commissioning contract, are shown in Appendix 1.

2.3 Approach

Part of the purpose of this review is to identify the questions that need to be answered in order to reduce the uncertainty around interactions between species and OREG during the consenting process. Currently, the limited ability to answer some basic questions relating to the existence, likelihood and potential consequences of specific risk factors requires regulators to take a very precautionary approach when assessing proposals ( i.e. the Precautionary Principle). In the medium to long term, these are the issues that will have most impact on the licensing process. Here we will deal with the potential harmful effects that have been identified in previous reviews (Wilson et al. 2007; Linley et al. 2009; Wilson & Gordon 2011). The simple aim is to identify the issues that may have an impact on marine mammal populations of interest to the Scottish Government. Targeting research resources on answering these questions, or at least reducing the uncertainty around such issues, should simplify the consenting process and reduce, or help target, the long term monitoring requirements thereby reducing unnecessary burden on developers.

2.4 Structure

This review will be broken down into the following sections.

In Section 3 we discuss the spatial and temporal overlap in marine mammal populations (and their associated parameters) and potential OREG stressors.

In Section 4 we consider potential proximate impacts. These are immediate effects on an individual. Impacts may cascade within an individual. For example, a proximate impact of displacement, caused by a stressor such as noise, may result in reduced foraging efficiency, resulting in reduced condition, then suppression of immune responses and reduced survivorship.

The linkages amongst proximate, secondary and ultimate consequences for individuals are discussed in Section 5.1. The effect of individual variability on population consequences can only be mediated though one (or more) of the three population vital rates: survivorship, fecundity and emigration. This is discussed in Section 5.2.

Within each section we highlight the most prominent gaps in knowledge. We regard data that have not been analysed and published as having the potential to fill currently existing research gaps. We also distinguish between on-going, funded work and work that has been proposed but has not yet secured funding. These research gaps are collated and prioritised in Section 6.

There is a need to coordinate OREG-relevant research to increase its efficiency and relevance. Appendix 2 contains a list of relevant UK, European and wider international working groups together with a list of Marine Renewable test centres where environmental impacts could be studied under controlled conditions and a list of recent and on-going funding programmes relevant to Scottish OREG developments.

Appendix 3 contains in depth information on the species covered in this report: harbour and grey seals; harbour porpoise; bottlenose dolphin; minke whale; white beaked dolphin; white sided dolphin; killer whale; Risso's dolphin; common dolphin; long finned pilot whales; striped dolphin; fin whale; Sei whale; humpback whale; sperm whale; Sowerby's beaked whale.

2.5 Report Review

The potential impact of OREG on marine mammals is a dynamic field, both scientifically and regulatory. Therefore, this report will be updated on an annual basis.