People over wind case: clarity or clear as mud?

How does the ruling in the People over wind case, which aims to conserve a protected species of pearl mussel, affect surveyors in practice? Will the legal uncertainty open up a rush of challenges in court?


  • Ben Standing

13 October 2020

A 2018 decision at the Court of Justice of the European Union (CJEU) in the matter of People Over Wind and Sweetman v Coillte Teoranta (C-323/17) has potentially altered the current UK position in relation to appropriate assessments under the Habitats Directive 92/43/EEC. It makes clear that mitigation measures should not be considered at the screening stage.

This means that those planning on developing near European protected sites will be more likely to have to prepare appropriate assessments to judge their impact on the environment, rather than relying on mitigation measures to avoid this stage.

However, the main difficulty is unlikely to be having to consider mitigation measures at the appropriate assessment stage – because if mitigation measures are required then a significant analysis of environmental impacts is likely to have been carried out already and so the amount of additional work is limited. The key difficulty is in understanding precisely what constitutes mitigation rather than the design of the project. This is likely to lead to greater uncertainty, both for developers and planning inspectors when considering if an appropriate assessment is necessary.

"The key difficulty is in understanding precisely what constitutes mitigation rather than the design of the project"


The Sweetman case concerned the decision to allow the laying of cables across 2 European special areas of conservation (SAC) by Coillte, a company owned by the Irish State that operates in the forestry sector. Both the SACs are in the Republic of Ireland. The cables are intended to connect wind turbines to the electricity grid and concerns have arisen that the project may have a significant impact on a protected species of freshwater pearl mussel.

The freshwater pearl mussel is significant because in 1991 it was estimated that there were 20,000 individuals. Current estimates suggest that there are only 300 and that it hasn’t reproduced since 1970. It is thought that sedimentation on the bed of the River Nore inhibits the successful restocking of the river by juveniles.

There are concerns that laying cables would significantly increase sedimentation. Coillte contended that it wouldn’t because the planning permission required cables to be laid in accordance with a construction management plan designed to prevent sedimentation. However People Over Wind and Peter Sweetman – prominent environmental campaigners – raised concerns about how effective this would be, especially because an appropriate assessment under the Habitats Directive had not been carried out.

Under Article 6 of the Habitats Directive 92/43/EEC (the directive) planning permission can only be granted if:
  • There is no adverse affect on the integrity of the protected area [SAC], caused by the development, either during construction or the ongoing operation of the development. Or
  • Where there is of an adverse effect on the integrity the protected area [SAC] and no mitigation can remove that risk, permission can only be granted where there are reasons of overriding public interest (including social or economic matters). In addition, Member States’ must take all compensatory measures necessary to ensure the coherence of Natura 2000 is protected.
The developer sought planning permission which was subsequently granted. Coillte instructed consultants to complete a screening report to identify whether there would be any risks to the river and or freshwater pearl mussel when the cables were laid.
The report concluded:
  • "(a) in the absence of protective measures, there is potential for the release of suspended solids into waterbodies along the proposed route, including direction drilling;
  • (b) With regards to the [pearl mussel], if the construction of the proposed cable works was to result in the release of silt or pollutants such as concrete into the pearl mussel population area of river… there would be a negative impact on the pearl mussel population. Sedimentation of gravels can prevent sufficient water flow through the gravels, starving the juveniles of oxygen."
The court heard that the species is nearing extinction, having not reproduced since 1970 because of the juveniles’ vulnerability to sedimentation. Nonetheless, it was concluded by the screening report that appropriate assessment under the directive was not required because of the protective measures that had been built into the work design of the project. These protective measures consisted of a construction methodology to control surface run-off into watercourses.

The Centre Européen de coopération juridique (CECJ) considered: ‘Whether, or in what circumstances, mitigation measures can be considered when carrying out screening for appropriate assessment under Article 6(3) of the Habitats Directive’.


The CECJ highlighted that the directive does not refer to mitigation; only conservation, prevention and compensation. The CECJ therefore interpreted mitigation to mean: "(26)… measures that are intended to avoid or reduce the harmful effects of the envisaged project on the site concerned".

In considering the requirements for appropriate assessment under the directive, the CECJ concluded that the only requirements were that:
  • the plan or project is not necessary for the management of the special protection area
  • it must be likely to have a significant effect on the site.
Therefore, in resounding terms, the CECJ concluded that the very fact that mitigation was required meant that the plan or project would significantly affect the special area of conservation. In such a scenario, an assessment should be carried out so that the adequacy of mitigation measures could be considered with the benefit of a full appropriate assessment — which would provide the decision maker with significantly more information.

The CECJ concluded that: “(37)… taking account of such measures at the screening stage would be liable to compromise the practical effect of the Habitats Directive in general, and the assessment stage in particular, as the latter stage would be deprived of its purposes and there would be a risk of circumvention … which constitutes … an essential safeguard provided for by the directive.”

Impact on the UK

In quite the opposite frame of mind, the UK has previously followed case law as set down in R (on the Application of Hart DC) v Secretary of State for Communities and Local Government [2008] EWHC 1204 (Admin) which concluded:

“(61) … if the competent authority is satisfied at the screening stage that the proponents of a project have fully recognised, assessed and reported the effects, and have incorporated appropriate measures when deciding whether an appropriate mitigation measures into the project, there is no reason why they should ignore such measures when deciding whether an appropriate assessment is necessary… as a matter of common sense, anything which encourages the proponents of plans and projects to incorporate mitigation measures at the earliest possible stage in the evolution of their plan or project is surely to be encouraged.” (Emphasis added).

The interpretation of the Directive, as incorporated into UK law by the Conservation of Habitats and Species Regulations 2017, may have a significant effect on developers in terms of costs and delays as the number of appropriate assessments required could increase. It may also make it more difficult for anyone carrying out environmental assessments, as they will need to understand what is mitigation and what is the design of the plan or project.


Primarily the issue relates to the definition of ‘plan or project’ as used by the CECJ in People Over Wind and Sweetman. The case implies that 'plan or project' does not include mitigation measures built in and only relates to the core intention of the plan or project.

In the Sweetman case, the court’s position is understandable. In my opinion it is the right decision, considering the acknowledgement that the plan or project would risk a critically endangered species and the description of the mitigation as “protective measures that have been built into the work design of the project”. It is logical that these protective measures are considered further by way of an appropriate assessment to better understand their effectiveness.

However, there is a difference between protective measures and the way that the project is structured. In some cases it is easy to distinguish, for example, when acoustic screens are installed to reduce the effects of noise on sensitive habitats; this is likely to be mitigation.

Mitigation or assessment?

The situation is more difficult when a project has been structured to avoid any impact on interest features, if for example it is carried out only at certain times of the year or in certain places. Does this account as mitigation, or should an appropriate assessment be carried out?

On the one hand it is arguable that the more information provided the better to allow an informed decision to be made. However, the disadvantage is that the 2017 regulations can create an unnecessary burden and cost on those carrying out plans and projects.

For example, where there is an intention to build a bridge over water in which a protected species of bird feeds, mitigation may necessarily be to make the bridge design higher to ensure that there is no restriction on the birds’ access to the water. To remove the mitigation would be to remove the very design of the bridge and consequently the plan may become very difficult to consider as part of an appropriate assessment.

It will be interesting to see how such an interpretation unfolds in practical terms. A number of inspectors have already requested that local planning authorities revisit the evidence behind their draft local plans. At the time of writing there hasn’t yet been a legal challenge regarding what is mitigation as opposed to the design of the project.

"It will be interesting to see how such an interpretation unfolds in practical terms"

In my experience screening decisions that consider mitigation measures effectively end up as appropriate assessments because of the amount of information required to ensure that there is no likely significant effect. I think we are more likely to see plans and projects subject to appropriate assessment, although for the reasons set out above the amount of additional work might not be that much more. Those wishing to avoid preparing an appropriate assessment will need to provide very clear reasoning to the local planning authority.

Some legal uncertainty remains, which provides an opportunity for those opposed to projects to bring a challenge based on failing to comply with the habitats regulations. When a challenge is brought hopefully it will provide clarity rather than muddy the waters further. However, considering the prime minister’s recent negative comments regarding habitats law it is possible that we might see further amendments to the habitats regulations shortly, thus avoiding the issue.

Related competencies include: Environmental assessment, Environmental audit (and monitoring), Legal/regulatory compliance

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