Offshore wind - compensating for adverse effects on Protected European Sites: statutory guidance 2026

7. Evidence Requirements

This section sets out the evidence that plan or project promoters must provide to support the identification, assessment and securing of compensatory measures.

In all cases, promoters should:

• use appropriate evidence-based justifications;

• clearly explain assumptions, methods and limitations; and

• set out the level of confidence associated with the evidence, drawing on recognised approaches to assessing confidence where appropriate.

7.1 Evidence Requirements (All Tiers)

Plan and project promoters must provide sufficient, proportionate evidence to enable the assessment of proposed compensatory measures. This should include but is not limited to:

• A clear description of the proposed measure(s) including the pressure being addressed and evidence of need, the spatial scale and location of the measure(s) with justification and evidence of site suitability (e.g. habitat condition/suitability, baseline characteristics, and historical extent).

• A justification of the measure(s) including:

  • the magnitude of the predicted adverse effect, taken only from the conclusions of the HRA Appropriate Assessment;

  • the anticipated ecological benefits of the measure(s) and how these align with the relevant compensation obligation (including considerations in section 7.2);

  • any additional benefits to the UK MPA Network (including considerations in section 7.3);

  • a reasoned justification for progression through the compensation hierarchy, including compensatory measures considered at each tier and evidence of their ecological effectiveness and feasibility (including considerations in section 5.6);

  • evidence that the measure(s) are proportionate to the predicted adverse effect (including considerations in section 7.7); and

  • an assessment of additionality (including considerations in section 8).

  • a description of how identified risks and uncertainties will be managed and addressed, with reference to proposed risk management and adaptive management plans; and

  • proposed monitoring arrangements (including considerations in section 11).

• A clear description of how the measure(s) will be secured, delivered and maintained including confirmation that the measure(s) have or can be secured within an appropriate timeframe (including post‑consent), taking account of any permits or licences required, access requirements, and any seasonal constraints.

• A clear description of the intended outcomes of the measure(s) including clearly defined success criteria, an assessment of confidence in achieving these and, expected timescales for delivery and effectiveness, including whether benefits will be realised in advance of impacts (including considerations in section 7.4).

• Detail on risk management and assurance (including considerations in section 10) including:

  • an assessment of risks, uncertainties and potential unintended consequences associated with delivery of the measure(s), including supporting evidence and details of how these have been identified;

  • a description of how identified risks and uncertainties will be managed and addressed, with reference to proposed risk management and adaptive management plans; and

  • proposed monitoring arrangements (including considerations in section 11).

7.2 Evidence of the Benefit to the Feature being Compensated for

Plan or project promoters must provide an appropriate evidence-based justification explaining how the measure is expected to deliver direct and/or indirect ecological benefit to the impacted feature, and over what timeframe.

Where direct evidence is not available, or where there is significant uncertainty in establishing a direct link to the impacted feature, project or plan promoters should present an appropriate evidence-based justification to demonstrate a clear ecological pathway linking the proposed measure to its expected benefit. Logical inference may suffice particularly for Tier 3 measures.

Evidence should address the following considerations, where relevant, to demonstrate the anticipated ecological benefit of the proposed measure:

• the scale and durability of the anticipated benefit to the benefiting feature e.g. immediate and long term, including long term maintenance requirements;

• the ecological effectiveness of the measure in delivering intended outcomes;

• the spatial relationship between the compensatory measure and the predicted impact;

• the conservation status or vulnerability of the benefiting feature (e.g. Annex I status, red‑listed species^[15]);

• the ecological relevance of the benefitting feature within the European site network or wider UK MPA network; and

• any management measures required to maintain the effectiveness of the compensatory measure over time.

7.3 Evidence of Additional Benefits to the UK MPA Network from the Measure

Where applicable, plan or project promoters must provide evidence of wider ecological benefits to the UK MPA network and the marine environment that supports it and over what timeframe.

Providing this evidence helps Scottish Ministers to:

• understand how the proposed compensatory measures contribute beyond addressing the immediate impact;

• assess whether measures deliver network‑scale ecological value, particularly for tier 2 and tier 3 compensation; and

• determine whether the compensation proposal represents an effective and reasonably proportionate response to the adverse effects on the impacted site.

Evidence may include information demonstrating that a proposed measure contributes to network‑scale resilience, connectivity, stability or adaptive capacity.

Relevant considerations may include but are not limited to:

• the number and type of protected features likely to benefit from the compensatory measure across the European site network and/or the UK MPA network;

• the ecological relationship between the benefitting feature and the impacted feature;

• the contribution of the compensatory measure to wider European site network or MPA network resilience, including enhancement connectivity, ecological coherence, adaptive capacity or resistance to pressures such as climate change; and

• the extent to which the measure contributes to recognised conservation strategies, plans or programmes, such as the Scottish Seabird Conservation Action Plan or the Marine and Coastal Restoration Plan.

7.4 Success Criteria

All compensatory measures, regardless of tier, must include clearly defined success criteria that are SMART (Specific, Measurable, Achievable, Relevant and Time‑bound).

Success criteria must be capable of being effectively monitored and reported against over time.

Each compensatory measure must be supported by a robust adaptive management plan, including clearly defined trigger points that specify when corrective action will be taken if monitoring indicates that ecological benefits are not being delivered as predicted (see section 10.2 for detailed adaptive management requirements).

Success criteria must be specific to the compensatory measure proposed and designed to demonstrate that the measure:

• is being implemented as intended; and

• is on track to deliver its intended ecological benefits.

For tier 2 and tier 3 measures, it may not always be possible to demonstrate a direct ecological benefit to the impacted feature. In such cases, success criteria should instead focus on:

• the delivery metrics associated with the feature or features the measure is intended to benefit; and

• the expected ecological benefits of the measure.

Success criteria should relate to how effectively and within what timeframe the compensatory measure is delivered. Success criteria must demonstrate that the measure has been implemented as intended and to an ecologically appropriate standard. Where relevant, this may include indicators such as establishment, spatial coverage, habitat condition or density.

Success criteria should also relate to whether the intended ecological outcomes of the compensatory measure are being achieved, and the timescales over which benefits are expected to arise, recognising that there may be a lag between implementation and full ecological functioning.

7.5 Confidence in Likely Success

Plan or project promoters must provide a reasoned assessment of confidence that the compensatory measure will deliver its intended outcomes within the expected timeframe, based on an appropriate evidence-based justification.

This assessment may consider, but is not limited to, the following factors, where relevant:

• technical feasibility and deliverability of the measure (including the ability to secure the compensatory measure);

• the current level of ecological understanding and any evidence gaps;

• dependencies on other activities or actions;

• vulnerability to external factors (including climate change);

• evidence from comparable or previously implemented measures from offshore wind or other industries;

• feasibility and limitations of monitoring success criteria;

• expected timescales for benefits to arise; and

• the overall robustness of the evidence base underpinning the measure.

Any assumptions used in assessing confidence must be clearly stated. This guidance does not require the use of a specific confidence‑scoring methodology; however, where a particular methodology is applied, its use must be justified.

Where uncertainty is higher, such as where measures are novel, technically complex or ecologically less well understood, greater levels of risk management may be required (see section 10). This will be assessed on a case-by-case basis.

In some circumstances, testing or trialling of a measure may be appropriate prior to full implementation. Where this is proposed, the implications for delivery timescales must be clearly set out in the compensation plan.

7.6 Assessment of Risk of Unintended Consequences

Plan or project promoters must undertake a review of potential direct and indirect adverse effects that may arise from implementing the proposed compensatory measure, including impacts on habitats, species interactions, and wider ecosystem processes.

An assessment of any potential socio‑economic impacts resulting from implementation of the compensatory measure must also be provided, where relevant.

Plan or project promoters should draw on appropriate evidence-based justifications to identify, assess and mitigate these risks at an early stage in the design process. This is to ensure that compensatory measures do not create new pressures, unintended adverse effects, or undermine anticipated ecological outcomes.

Where appropriate, promoters should seek advice from the relevant SNCB to inform risk identification and mitigation.

7.7 Making the Case for Reasonably Proportionate

Plan or project promoters must present a clear and evidence‑based justification demonstrating that the proposed compensatory measure, or package of measures across tier 1, tier 2 and/or tier 3, is reasonably proportionate to the predicted adverse effects identified in the Appropriate Assessment.

This must include a transparent comparison between the magnitude and nature of the adverse effect and the anticipated ecological benefits delivered by the compensatory measures. The approach taken should reflect the role of each tier: direct feature‑specific benefits at tier 1, broader benefits to ecologically similar features at tier 2, and UK MPA network‑scale benefits at tier 3.

For tier 1 measures, reasonable proportionality will normally be demonstrated through direct, feature‑specific ecological evidence. For tier 2 and tier 3 measures, where benefits may be delivered through wider or more indirect ecological pathways, a greater degree of expert ecological judgement may be required. Any such judgement must be transparent, evidence‑based and apply the appropriate level of precaution.

Where uncertainty remains, demonstrating reasonable proportionality may require additional compensation, enhanced monitoring and adaptive management arrangements, in accordance with this guidance.

7.8 Acceptable Standards of Evidence

Appropriate sources of evidence may include, but are not limited to:

• peer‑reviewed scientific literature;

• published grey literature (where methodology and limitations are transparent);

• outputs from relevant research projects or programmes;

• expert advice from SNCBs;

• published Government conservation strategies, plans or policies, and other national or regional action plans;

• data from national or regional monitoring programmes, for example seabird census or population trend data establishing baselines or pressures;

• expert elicitation, where structured and appropriately documented;

• site‑specific ecological surveys relevant to the proposed measure, such as predator presence/absence surveys, habitat condition assessments, or biosecurity assessments;

• spatial or ecological modelling used to predict ecological responses or demonstrate anticipated benefits (for example Population Viability Analysis or Habitat Suitability Modelling), where assumptions and limitations are clearly explained;

• evidence from previous compensatory measures or comparable environmental projects, including information on whether such measures were effective;

• evidence from ecologically similar species, ecosystems or locations, where direct evidence is limited, supported by clear ecological reasoning;

• desk‑based studies where these are considered sufficiently robust and objective by the regulator and relevant SNCB; and

• international examples or research, where UK‑specific evidence is limited or unavailable.

7.9 Dealing with Limited or Uncertain Evidence

Where the scientific evidence base is limited, for example for novel, untested or emerging compensatory measures, plan or project promoters must incorporate additional risk management (see section 10) to manage uncertainty.

This may include, but is not limited to:

• delivery of a greater scale of compensation than would otherwise be required (over‑compensation);

• enhanced adaptive management frameworks, incorporating iterative decision‑making, monitoring and evaluation;

• more intensive or targeted monitoring to improve understanding of whether success criteria are being met; and/or

• allowing longer timescales for ecological benefits to emerge and be demonstrated.

The level of risk management must be proportionate to the degree of uncertainty and clearly justified using the available evidence.