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Purpose and Context of the Guidelines
Relationship with other Guidance
The Aims of the Ecological Assessment Process
Contents of these Guidelines


1.1 The marine environment is a vast natural resource that forms a major part of this planet’s life support system. It provides a range of ecosystem services including: food, raw materials, the means of transporting goods, energy in various forms and recreational opportunities. Beneath the sea lie important reserves of raw materials, especially oil, gas, minerals and aggregates. The waves and tides, together with wind, have the potential to provide major sources of renewable energy. Thus, it is not surprising that there are ongoing challenges arising from pressure to maximise use of these resources whilst maintaining its natural attributes, both for their intrinsic value and their contribution to the life-support system that we depend upon. Much of the Continental Shelf is far from pristine: it has been exploited in many ways over time and the pace of exploitation is accelerating.

1.2 To avoid further deterioration and to facilitate recovery of the marine environment a comprehensive understanding of the implications of a development is a pre-requisite. The approach needs to be rigorous, transparent, evidence based and scientifically robust. Achieving such aspirations is complicated because the marine environment is more difficult to work in than terrestrial environments. Much less is known about the distribution of marine biodiversity life than of terrestrial ecosystems, and acquiring new information can be very expensive and time-consuming. This means that the process of rigorous assessment holds many challenges, and that there will often be considerable uncertainty about what will be found.

1.3 Experience gained from terrestrial developments alone cannot be relied upon and there is a need to develop a comparable understanding of cause and effect relationships. This is an ongoing process that will evolve with time. Meanwhile, new projects should be evaluated according to established procedures, taking account of what is already known, in conjunction with the results of newly commissioned EIA. IEEM encourages all EIA practitioners to share the data and results of their investigations with the wider community. This would include the publication of findings in journals so that we may all learn and improve our decision making.

1.4 The process of evaluation relies upon Ecological Impact Assessment (hereafter referred to as EcIA) which has been defined as:

‘the process of identifying, quantifying and evaluating the potential impacts of defined actions on ecosystems or their components.

(Treweek, 1999)2

1.5 EcIA is a key component of Environmental Impact Assessments (EIAs), which are carried out to meet the requirements of Council Directive 85/337/EEC on the Assessment of the effects of certain public and private projects on the environment3, as amended by Council Directive 97/11/EC4. The statutory instruments that implement these Directives in the UK together with associated guidance are listed in Appendix 8 of Environmental Impact Assessment: guide to procedures5 and can be accessed via the HMSO’s web site6 and/or web sites of the UK Government and the devolved governments of Northern Ireland, Scotland and Wales. In the Republic of Ireland guidance is available from the EPA Guidelines on information to be contained in Environmental Impact Statements (EIS)7 and statutory instruments can be accessed via the Irish Statute Book8. The statutory instruments are particular to each country and to different types of development. Collectively, they are referred to throughout this document as the EIA Regulations. Where an EcIA is undertaken as part of an EIA, it is subject to the relevant EIA Regulations.

1.6 EcIA can also be undertaken to provide ecological information for development projects in near-or off-shore locations such as, ports, windfarms and those associated with oil and gas production. Where an application for consent is sought for which EIA is not required, EcIA can be used to guide the development brief and inform the management plan. This document is also intended to provide guidance for these circumstances. However, the assessment method and scope should be ‘fit for purpose’ i.e. it should reflect the spatial extent and zone of influence of the project, and the specific sensitivities of the location.

1.7 As the leading professional institute in Britain and Ireland for ecologists and environmental managers, IEEM seeks to advance the science and practice of ecology and environmental management for the public benefit, and to further environmentally-sustainable management and development. Therefore, IEEM emphasises the need for a scientifically rigorous and transparent approach to EcIA. The ecological component of an EIA, an EcIA or Appropriate Assessment (see para 5.8) should be undertaken by qualified professionals with experience in ecological survey and impact assessment and recognised by a relevant professional body e.g. IEEM.

1.8 These Guidelines have been developed with the participation of a wide range of interested parties to establish and set out accepted good practice for each stage in the EcIA process. They are based on an understanding of the legal requirements of the relevant international agreements and directives at the time of publication (Annex 1). Although these Guidelines are not legally binding, and other approaches may be valid and appropriate in some situations, they do set a standard of best practice in EcIA that IEEM believes to be appropriate to the professional standing of its members. For clarification of the legal requirements, users of these Guidelines should refer to the relevant legislation and case law, and if appropriate seek specialist legal advice.

1.9 These Guidelines offer the additional benefit of providing guidance to promoters of projects so that the rationale for approaches proposed by consultants is readily apparent. Similarly they provide regulators and decision-makers with an indication of the information they may need in order to adequately consider projects and their consequences in the light of nature conservation legislation and policy. Whilst not guaranteeing a positive outcome in the consents process, they do provide a means of building consensus with stakeholders such as Statutory Nature Conservation Organisations (SNCOs), Environmental Protection Agencies and environmental NGOs.

1.10 Legislation relating to the marine environment is rapidly evolving and practitioners should always check for changes and revisions. Developing legislation includes:

  • the Water Framework Directive9,10,11;
  • the EU Marine Strategy Framework Directive12;
  • the Environmental Liability Directive13,14;


  • the Marine and Coastal Access Act 2009 (England and Wales)15;
  • the Marine (Scotland) Act 201016,
  • a Marine Bill for Northern Ireland and
  • the European Communities (Marine Strategy Framework) Regulations 2010, Ireland.

1.11 These and related policy changes concerning requirements for EcIA, as well as developments in the science that underpins the assessment process, mean that periodic review and revision of these Guidelines will be necessary. (Also see 7.13.)

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Purpose and Context of the Guidelines

1.12 The purpose of EcIA is to provide decision-makers with clear and concise information about the likely ecological effects associated with a project and their significance both directly and in a wider context. Protecting and enhancing biodiversity and landscapes and maintaining natural processes depends upon input from ecologists and other specialists at all stages in the decision-making and planning process; from the early design of a project through implementation to its decommissioning.

1.13 These Guidelines provide practical advice for those engaged in EcIA for any type of project in the marine and coastal environments. They are intended for everyone engaged in the process, whether they are acting as advisers to or for:

  • the proponent e.g. the developer (required to provide necessary information);
  • a competent authority (charged with managing the statutory decision making process);
  • public bodies with biodiversity and landscape duties and/or WFD duties;
  • consultees (who may advise the competent authority in a statutory or voluntary capacity); or
  • any other party (e.g. a local campaign group, other members of the public or the media).

1.14 Whilst these Guidelines promote a scientifically rigorous approach, it is important to recognise that EcIA relies on ecologists using their professional judgement. Judgements should be made on the basis of an objective assessment of the best information available. Good communication throughout, but particularly at key stages, between ecologists and other professionals engaged in the assessment process (e.g. geomorphologists, hydrologists, EIA Coordinators); together with proponents and relevant specialists will reduce the risk associated with making such judgements. Where limitations are identified, these should be clearly stated and their implications considered. Limitations may include:

  • data, including accessibility and ability to gather data;
  • data sharing policies of developers;
  • time available for gathering data;
  • time of year of observations;
  • scientific understanding of ecological processes and drivers;
  • experience of the assessor;
  • information about the project;
  • project alternatives;
  • spatial, technological and construction operations;
  • experimental mitigation strategies;
  • commitment to delivery of mitigation and compensatory strategies;
  • enforcement of mitigation and compensatory strategies; and
  • unknown effects of novel developments.

1.15 Where there is reasonable doubt, a precautionary approach should be taken in accordance with recognised national guidance (for example, SNIFFER 200517).

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1.16 Consistent use of terminology is essential to avoid ambiguity in EcIA. A glossary of terms has been included (see Annex 1) to indicate how terminology has been used in these Guidelines.

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Relationship with other Guidance

1.17 These Guidelines have been developed to complement and expand upon guidance already published by IEEM on EcIA for terrestrial, freshwater and coastal environments. There will be examples, especially on the coast, where a project will be subject to both terrestrial and marine consent processes and consequently both sets of guidance may be relevant. For this reason we have sought to make the processes described here compatible with the terrestrial guidance In circumstances where ecologists are required to fit an assessment into a format that is inconsistent with this guidance an explanation should be given relating it to the approach recommended here.

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The Aims of the Ecological Assessment Process

1.18 Those engaged in EcIA should seek to obtain the best possible short- and long-term ecological outcomes from any changes in use of marine and coastal resources. It is important that all interested parties understand the process by which the assessment is made, and who is responsible for implementing and monitoring any actions needed to deliver biodiversity and landscape objectives. Therefore, EcIA must provide reliable information about, and interpretation of, the ecological implications of any project from its inception to its operation and, where appropriate, its decommissioning.

1.19 It is the role of all ecologists engaged in EcIA to:

  • describe the existing ecological baseline including the physical and chemical environment;
  • provide an objective and transparent assessment of the ecological effects (short, medium, long-term, synergistic, cumulative and in-combination) of the project to all interested parties, including the general public;
  • facilitate objective and transparent determination of the consequences of plans and projects in terms of international, national, regional and local policies relevant biodiversity and landscapes; and
  • set out the steps required to meet legal requirements relating to designated sites and legally protected or controlled species, whilst taking account of their ecosystem function and the wider environment.

1.20 There are duties placed on certain public bodies to further biodiversity, but these do not apply universally. IEEM endorses the principles recommended by the Royal Town Planning Institute18 in relation to terrestrial applications, for optimising the benefits of planning and other regulatory decisions to ecology and biodiversity. These principles are equally applicable in the marine environment and are as follows:

Obtain sufficient information on the environmental resources and natural processes to assess the impacts of the project.

Consider options that avoid harm to environmental resources or natural processes.

Where adverse effects are unavoidable then these should be mitigated either through the design of the project or through measures that can be subsequently guaranteed – for example, through a condition or planning obligation.

Where, despite the mitigation proposed, there are significant residual adverse environmental effects these must be offset by appropriate compensatory measures nearby/elsewhere.

New Benefits:
Seek to provide net benefits for biodiversity over and above requirements for mitigation or compensation.’

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Contents of these Guidelines

1.21 This guidance is structured around the main stages in the EIA process (see Box 1) as these are relevant to most EcIAs, whether or not they are undertaken as part of an EIA. Although described in this staged way, it is important to recognise that EcIA is an iterative process, with early stages (notably project design and scoping) having to be revisited as the assessment proceeds.

1.22 Chapter 2 outlines the ecological considerations that relate to the task of determining whether or not an EIA is required ‘screening’ and addresses the task of ‘scoping’ an EcIA.

1.23 It may not be appropriate or necessary to study all possible ecological impacts to the same level of detail. Effort must be focused on those features or resources that are sufficiently important to merit more detailed consideration and/or where the impacts arising from the project are known to have greatest effect. A clear rationale should be given for deciding those features and resources that should be subject to more detailed consideration (a key purpose of scoping). This will enable all those engaged in the assessment to understand the reasoning behind the scope of investigations. Policy considerations will influence the criteria that will be appropriate for determining the threshold in any particular case.

1.24 Chapter 3 considers ‘setting the baseline’, the determination and assessment of data to set the context and to provide the basis for the evaluation of impacts.

1.25 Chapter 4 describes ecological ‘valuation and evaluation’, the assigning of relative values to ecological features and resources including those that have been designated for their nature conservation interest.

1.26 Chapter 5 discusses the concept of ‘significance’, which lies at the heart of EcIA and subsequent decision-making. An EcIA must include a description of the ecologically significant impacts of a project and of how likely they are to occur. This, together with the value of the affected resource or feature, should then be given due consideration; firstly when identifying the need for mitigation and secondly, in determining whether to give consent to a particular project and the conditions or legal obligations that should be attached to this consent in order to safeguard biodiversity and landscape interests.

1.27 There are differences in the various criteria currently used for determining whether the impacts to ecological interests are significant and decisions in this regard are often subjective. This guidance details a systematic and consistent approach to determining whether impacts are significant. This should help to reduce the need for subjective judgement. In this guidance a significant impact, in ecological terms (whether negative or positive), is defined as an impact on the integrity of a defined site or ecosystem and/or the conservation objectives for the habitats or species within a given geographical area. Integrity is defined here as the coherence of a site’s ecological structure and function across its whole area that enables it to sustain the habitat, complex of habitats and/or levels of populations of the species and inter-relationships between species and habitats, for which it was classified. It is recognised that it may not be easy for practitioners to assess the site’s coherence when working offshore. However, it is important that this should be done.

1.28 Chapter 6 provides advice on ‘mitigation’, ‘compensation’ and ‘enhancement’. It is important to ensure that any significant residual impacts are clearly identified after taking mitigation into account; in such cases compensation may be necessary. Recent developments in planning policy have emphasised that the enhancement of biodiversity is a proper criterion for evaluating a development project and ecologists can play a key role in identifying the opportunities to achieve this goal.

1.29 Chapter 7 sets out the consequences of a significant impact, in terms of the legal and policy framework within which a decision should be taken by a competent authority.

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 Box 1: EcIA Process

Initial project design

At the outset of the project, the proponent’s ecologist(s) should:

  • obtain information on the project, any alternatives that have been studied and existing ecological information;
  • undertake a gap analysis between known and needed information and plan and prioritise gap filling;
  • review ecological implications of alternatives;
  • discuss key ecological considerations about the project design (and alternatives) with the proponent and the design team (e.g. engineers, architects);
  • avoid impacts but if this is not possible then modify the project to reduce negative ecological impacts; and
  • explore opportunities for ecological enhancements as early as possible.

Screening (EIA only)

The proponent may seek a formal screening opinion from the competent authority to determine the need for EIA under the EIA Regulations.

  • For Schedule 1 projects, EIA is mandatory.
  • For Schedule 2 projects the need for EIA is determined based on the significance of anticipated environmental effects as influenced by, inter alia, the nature, size and location of the project. Ecologists working for the competent authority will need to determine whether significant impacts to ecological features are likely. The decision will be based on the criteria set out in the relevant EIA Regulations for establishing whether or not EIA is required and should take into account the guidance provided in Chapters 3, 4 and 5 of these Guidelines.

Scoping EcIA

Where an EIA is required the proponent may seek a formal scoping opinion from the competent authority to determine the issues to be covered by EIA. In all other cases it is advisable to seek the competent authorities and key consultees’ views on the proposed scope of the EcIA (to agree the possible effects to be investigated and the assessment methods to be used).

Scoping should:

  • involve consultation/formal discussions with other members of the EcIA team (i.e. including the proponent’s ecologists and those of the competent authorities, statutory agencies and possibly the NGOs);
  • involve appropriate consultation with regulatory bodies regarding the proposed scope of the assessment;
  • identify non-statutory consultees;
  • identify any potential licensing requirements for survey and/or development regarding legally protected species;
  • identify all proposed construction, operating, maintenance, closure and decommissioning activities that may generate significant ecological impacts;
  • identify significant other developments within the zone of influence that may give rise to cumulative/in-combination/synergistic effects;
  • identify potentially important ecological features or resources;
  • identify for assessment (which should be undertaken at the optimal survey time for the relevant biodiversity) those important ecological features or resources that could sustain significant positive or negative impacts,;
  • identify relationships with other issues e.g. water, landscapes, seascapes;
    identify data gaps;
  • propose suitable spatial and temporal scopes for the assessment and identify the main ecological issues to be addressed;
  • undertake preliminary assessment of potential ecological impacts on identified features or resources, incorporating existing data/information;
  • reconsider spatial and temporal scope and amend the extent of preliminary investigations if necessary;
  • list those receptors and features that do not need further assessment;
  • recommend suitable survey/research methodologies that have been agreed with consultees;
  • result in a scoping report/summary that can be circulated for comment and modified accordingly;
  • confirm potential opportunities for avoidance of impacts to, or enhancement of, biodiversity; and
  • ensure compliance with standards and consistency with formal methods of evaluation.

Impact assessment

The EcIA team will be involved in the following assessment process, which should cover construction, operation maintenance, closure and decommissioning stages of any project:

  • determine the value of ecological features and resources affected, through survey and/or research;
  • assess potential impacts affecting those important features and resources, which meet or exceed a defined threshold value, with reference to ecological processes and functions as appropriate;
  • quantify the extent, magnitude, duration, timing and frequency of the impacts;
  • identify cumulative and in-combination impacts;
  • assess impact reversibility;
  • explain the level of confidence in these predictions; and
  • identify likely significant impacts in the absence of any mitigation.

The surveys and research that are undertaken may indicate that the scope of the assessment should be adjusted and further studies carried out.

Evolution of project design and mitigation

  • Consider alternative location(s) or layouts for the proposed development;
  • identify measures to avoid or reduce negative impacts e.g. site layout;
  • identify opportunities for enhancement;
  • demonstrate likely success of mitigation measures;
  • design and agree monitoring strategy and monitoring of mitigation performance with consultees; and
  • provide sufficient information for mitigation measures to be implemented effectively, e.g. through an Environmental Action Plan (EAP).

Identify significant residual impacts and their legal, policy and development control consequences

  • Produce a clear summary of the significant residual impacts of the project following incorporation of avoidance, mitigation and enhancement measures;
  • consider the consequences of significant residual impacts on the features of interest in the light of planning policies and legislation;
  • where significant negative impacts cannot be avoided, identify compensation measures to be implemented; and
  • include mitigation, compensation and enhancement measures in the EAP or similar.


The final EcIA report or, for EIAs, the Environmental (Impact) Statement should clearly set out all the ecological information necessary for a decision to be made. Key aspects include a description of the following:

  • ecological baseline and trends if the project were not to go ahead;
  • criteria used to evaluate ecological features and resources;
  • criteria used to assess the significance of impacts of the project;
  • justification of methods used; and
  • legal and policy consequences;


  • the identification of likely impacts (positive and negative) to ecological features and resources together with an explanation of their significance and the level of certainty with which this can be stated;
  • a note of any key data that were unavailable or missing; and
  • a presentation of any analytical techniques used and the analysis itself;

Follow-up and monitoring

  • Confirm the implementation of conditions/planning agreements;
  • audit predicted impacts against the actual situation; and
  • take measures to rectify unexpected negative impacts, ineffective mitigation/compensation measures.

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