Ecological Impact Assessment (EcIA)

The Role of an Ecological Impact Assessment

An Ecological Impact Assessment (EcIA) is a structured, evidence-based process through which the effects of a proposed development project on wildlife, habitats and ecosystems are formally identified, evaluated and addressed.

It goes beyond recording what is present on a site: it analyses how development will affect those ecological features, predicts the potential impacts of those effects, and sets out what must be done to avoid, reduce or compensate for harm.

For developers, housing providers and landowners, an EcIA is the document that demonstrates to a local authority that the ecological consequences of a development proposal have been properly understood and professionally managed.

Without it, many applications, particularly those on sites with known or suspected ecological interest, cannot be determined lawfully. 

The Difference Between an EcIA, an EIA and a PEA

These three types of ecological assessment sit at different levels of the planning process, and understanding how they relate to each other is important for commissioning the right work at the right stage of any property or land development.

A Preliminary Ecological Appraisal (PEA), sometimes called an extended Phase 1 habitat survey, is the initial survey stage of ecological assessment for most development sites.

This ecology report involves a desk study and a site walkover to map habitats and identify the potential for the presence of protected species.

These ecological walkover surveys establish baseline information that indicates whether further ecology surveys are needed. It is the starting point, not the end product.

An Ecological Impact Assessment is the detailed follow-on from a PEA.

Where the preliminary appraisal has identified habitats or species that require closer examination, or where the scale or nature of the development warrants a comprehensive ecological baseline, the EcIA provides that level of evidence, especially where present protected species are involved.

The assessment process involves targeted species surveys, threatened species, detailed habitat mapping and a systematic assessment of how the proposed development will affect the ecological features recorded.

An Environmental Impact Assessment (EIA) is a broader process that examines all the potentially significant environmental effects of a development, including noise, traffic, air quality, landscape, heritage and human health, as well as ecological issues and likely ecological constraints.

Under the Town and Country Planning (Environmental Impact Assessment) Regulations 2017, certain categories of development above defined thresholds are required to undergo a formal EIA, which results in an Environmental Statement submitted alongside the planning application.

Where an EIA is required, the EcIA becomes the ecology and biodiversity chapter of that Environmental Statement.

For smaller projects that fall below the EIA threshold, a standalone EcIA addresses the ecological dimension without the full EIA apparatus.

The ecological survey process for both a standalone EcIA and the ecological chapter of an Environmental Statement follows the same professional methodology; the difference is the wider context in which the assessment sits.

When is an Ecological Impact Assessment Required?

An EcIA is required in a range of circumstances.

The common thread is that a proposed development site has the potential to cause significant effects on the natural environment, and the planning authority needs robust ecological evidence before it can lawfully determine the application.

An EcIA is most commonly needed where a Preliminary Ecological Appraisal has identified important habitat types or species that require detailed assessment and where the scale or type of development proposed means that significant ecological effects are reasonably foreseeable.

Developments affecting or adjacent to designated sites, including Sites of Special Scientific Interest (SSSIs), Special Areas of Conservation (SACs), Special Protection Areas (SPAs) and Ramsar sites, will almost always require an EcIA as part of or in support of a Habitats Regulations Assessment.

Sites containing or adjacent to ancient woodland, priority habitats, watercourses or areas known to support protected species are likely to require an EcIA regardless of the scale of the proposed development.

For larger or more complex developments like major housing schemes, commercial and industrial proposals, infrastructure projects, or any development where there is a formal EIA ecology survey required under the 2017 Regulations, an EcIA requirement is standard practice.

Local planning authorities routinely request this level of evidence as a condition of determining such applications, either at the pre-application stage or as a formal planning condition.

The earlier an EcIA is commissioned in the project timeline, the better. Many of the targeted ecological surveys that feed into it – bird surveys, red squirrel surveys, bat surveys, newt surveys, dormouse surveys, reptile surveys and botanical assessments – are seasonal, and missing the right survey window can delay the entire planning programme by months.

Engaging an ecology consultancy at the design stage, before the scheme is fixed, also creates the opportunity to adapt the development layout in response to ecological constraints, which is almost always less disruptive and less costly than retrofitting ecological mitigation later in the development process.

UK Wildlife Law

The requirement to consider ecological impacts as part of the planning process is embedded in UK legislation and planning policy, even though there is no single statute that directly mandates an EcIA by name.

Relevant legislation is included in the Wildlife and Countryside Act 1981 (as amended) which protects a wide range of animal and plant species and prohibits activities that damage or destroy protected species or their habitats.

The Conservation of Habitats and Species Regulations 2017 provides additional protection for European protected species, including bats, great crested newts, dormice, breeding birds, otters and white-tailed eagles, and requires competent authorities – including local planning authorities – to assess the effects of development on protected habitats and species before granting consent.

The Natural Environment and Rural Communities Act 2006 places a duty on all public authorities, including planning authorities, to have regard to conserving biodiversity when carrying out their functions.

The Environment Act 2021 introduced mandatory biodiversity net gain for most developments in England, requiring an evidenced ecological baseline and a demonstration that development will leave biodiversity measurably better off.

The National Planning Policy Framework (NPPF) sets out clear expectations for the planning system to protect and enhance the environment.

It requires planning decisions to protect and enhance biodiversity and geological conservation, avoid harm to irreplaceable habitats, and minimise impacts on and provide net gains for biodiversity.

These policy requirements cannot be satisfied without a credible, evidence-based ecological assessment conducted by an experienced ecological consultancy.

The professional standard for EcIA practice is set out in the Chartered Institute of Ecology and Environmental Management (CIEEM) Guidelines for Ecological Impact Assessment in the UK and Ireland, currently at version 1.3, published September 2024.

These guidelines cover terrestrial, freshwater, coastal and marine contexts and are the primary reference document used by ecology consultants and local authority ecologists when preparing and reviewing EcIA reports.

The CIEEM EcIA Checklist, developed jointly with the Association of Local Government Ecologists (ALGE), provides a quality assurance framework used by both practitioners and planning officers when reviewing reports.

The British Standard BS 42020:2013 – Biodiversity: Code of Practice for Planning and Development – also provides relevant guidance on the integration of biodiversity considerations into the design and planning process.

How is an Ecological Impact Assessment Carried Out?

The EcIA process follows the methodology set out in the CIEEM guidelines, adapted proportionately to the scale and complexity of the development plans and the ecological characteristics of the site.

It is an iterative process; later stages of the assessment may generate information that informs earlier stages, and the assessment should be updated if the scheme design changes materially during the planning process.

Scoping and Desk Study

The process begins with a scoping exercise to define the study area, identify the ecological features that are likely to be relevant to the assessment, establish the information sources to be consulted and agree the survey methodology with the local planning authority or its ecological advisers where appropriate.

Scoping ensures that the assessment is focused on the features that matter and avoids unnecessary work on those that do not.

The desk study compiles existing data on the ecology of the site and its surroundings, drawing on local biological records from county record centres, data from Natural England (NE) and other statutory bodies, information on designated sites within the relevant search radius, published species distribution data and any previous ecological survey reports covering the site or the wider area.

This background information shapes the baseline assessment, informs further action and the design of the field survey programme.

Baseline Ecological Survey

The desk study findings are followed up with a field survey programme designed to establish the ecological baseline of the site: the full picture of what is present before development takes place.

The ecological survey programme will typically include a preliminary ecological appraisal or walkover survey where ecological consultants map habitats across the site and identify features requiring further investigation, followed by targeted species surveys for any protected or notable species identified as potentially present.

Common targeted surveys for protected species include bat activity transects and roost emergence and re-entry surveys, great crested newt presence and absence surveys, reptile surveys using artificial refugia, breeding bird surveys, badger surveys, otter and water vole surveys, great crested newt surveys, giant hogweed surveys, Himalayan balsam surveys and botanical surveys for protected or priority plant species and communities.

Surveys for Japanese knotweed are commonly required, as well as surveys for white clawed crayfish, bat surveys to identify roosting sites, surveys for specific habitats, water voles, rare plants and vegetation surveys.

The specific surveys required will depend on the habitats present on the site, the specific species likely to use them, the time of year and the results of earlier survey visits.

An experienced ecology consultant will advise on the full survey programme needed and design it so that all required surveys can be completed within the appropriate seasonal windows.

Impact Assessment

The impact assessment evaluates how the proposed development will affect each of the important ecological features identified during the baseline survey.

Effects are characterised in accordance with the CIEEM guidelines, taking into account whether they are positive or negative, direct or indirect, temporary or permanent, reversible or irreversible, and whether they affect features of local, regional, national or international importance.

The significance of each effect is determined by professional judgement, drawing on the geographic frame of reference established in the CIEEM guidelines.

An effect is considered significant if it is sufficiently important to require reporting so that the decision-maker, typically the local planning authority, is adequately informed of the ecological consequences of the development. Significant effects can be positive as well as negative, and the assessment should identify both.

Cumulative effects – the combined effect of the proposed development alongside other existing or consented schemes in the area – must also be considered where relevant, and the assessment should address off-site features that may be affected by the development through drainage, lighting, noise, dust or other pathways.

Mitigation and Compensation

Where the impact assessment identifies significant adverse effects, the CIEEM mitigation hierarchy requires these to be addressed in a specific order.

The preferred response is always to avoid the impact through design: relocating built elements away from sensitive habitat, retaining existing ecological features, changing construction methods or timing.

Where avoidance is not possible, suitable mitigation strategies are designed to reduce the magnitude of the impact to an acceptable level.

Only where residual significant adverse effects remain after mitigation measures have been applied should compensation measures be considered; for example, the creation of replacement habitat off-site to compensate for habitat loss that cannot be avoided.

Enhancement measures such as improvements to the ecological value of the site beyond the mitigation of adverse impacts are required under the NPPF and the biodiversity net gain framework.

These might include the creation of new habitat features, the improvement of existing habitats in poor condition, the installation of bat boxes, bird boxes and other features for particular species, or the management of retained habitats to improve their condition over time.

The mitigation, compensation and enhancement strategy proposed in the EcIA forms the basis of the ecological commitments that will be secured through planning conditions or a Section 106 obligation, and feeds directly into any habitat management and monitoring plan required as part of the biodiversity net gain framework.

Reporting

The findings of the EcIA are presented in a written report, produced in line with the CIEEM Guidelines for Ecological Report Writing and the EcIA Checklist developed with ALGE.

The report sets out the methodology, the survey data, the impact assessment and its conclusions, and the proposed mitigation and enhancement strategy in a format that is clear, transparent and accessible to non-specialists as well as planning officers and statutory consultees.

A non-technical summary is typically included to make the key findings accessible to a wider audience.

Where the EcIA forms the ecology chapter of an Environmental Statement, it must integrate with the other technical chapters of the statement and contribute to the overall assessment of the development’s environmental effects.

What Happens After the EcIA is Submitted?

Once the EcIA has been submitted as part of or in support of a planning application, it will be reviewed by the local planning authority’s in-house ecologist or a specialist ecological consultee such as NE, Natural Resources Wales (NRW) or the relevant local wildlife trust.

The CIEEM/ALGE EcIA Checklist is commonly used by local authority ecologists and statutory consultees as a quality assurance tool when reviewing reports.

If the EcIA is considered adequate and the assessment concludes that the development can proceed with appropriate mitigation and enhancement, the local council will be in a position to grant consent, usually subject to ecological planning conditions.

These conditions will typically require the implementation of the mitigation and enhancement measures set out in the EcIA and, where relevant, the submission and approval of a habitat management and monitoring plan as a separate discharge condition.

Where the EcIA reveals that a European protected species licence is needed because the development cannot proceed without harming a protected species despite the application of the mitigation hierarchy, the licence application to NE or the equivalent devolved body will draw directly on the survey data and mitigation proposals in the EcIA. A licence cannot be applied for until planning permission has been granted.

Get Quotes from Trusted, Trained Ecologists

An EcIA must be carried out by a qualified ecology consultant with the experience, species survey licences and professional standing needed to produce a report that local planning authorities and statutory consultees will accept.

CIEEM membership and Chartered Ecologist status are recognised indicators of professional competence.

Where protected species surveys such as badger surveys, dormouse surveys or surveys for barn owls are required as part of the baseline assessment, the consultant must hold the relevant NE or NRW survey licence for the priority species concerned.

The starting point is almost always a Preliminary Ecological Appraisal, which establishes whether an EcIA is needed and what targeted surveys will be required.

Commissioning this early, before the scheme design is fixed, gives the ecology consultancy the best opportunity to identify ecological constraints, opportunities and a mitigation plan to advise clients at a stage when the development layout can still respond to them, avoiding costly delays.

Obtaining the relevant information from qualified ecological surveyors as early as possible is an essential part of satisfying planning requirements and complying with UK law.

Use our free service to get fast, no-obligation quotes from trusted ecology consultants in our network with a proven record of carrying out ecology survey services.

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