General approach and principles during screening and appropriate assessment

AuthorDirectorate-General for Environment (European Commission)
Guidance on Wind Energy Developments and EU Nature Legislation 27
This aim of this chapter is to provide guidance and good practices on some general issues that can arise
during the screening and appropriate assessment procedures, such as assess ing significance of the effects ,
the scoping procedure and setting a baseline. It also covers issues of uncertainty, cumulative effects and
stakeholder consultation.
3.1 Significance of the likely effects
Article 6(3) of the Habitats Directive refers to the need to assess the likelihood of a plan or project having
significant effects on a Natura 2000 site. The screening process assesses whether it is likely to have a
significant effect on the site. If significant effects cannot be excluded with certainty, an appropriate assessment
is necessary. The appropriate assessment assesses the likely effects on the Natura 2 000 site against its
conservation objectives and whether implementing the plan or project may or will adversely affect the integrity
of the site.
One of the major challenges faced when undertaking an assessment of a plan or project is how to understand
and determine when an effect is significant or not.
It is necessary first to explore the type and extent of effects (‘significant eff ect’), and then to explore the causes
likely to create such effects (‘likely to have either individuall y or in combination’). Determining whether a
plan or project is likely to have a significant effect will have practical and legal consequences. Therefore, when
a plan or project is proposed, it is important firstly that this key issue is consid ered, and secondly that the
consideration can stand up to scientific and expert scrutiny. The safeguards set out in Article 6(3) are triggered
not by a certainty but by a likelihood of significant eff ects. Mitigation measures cannot be taken into accoun t
at this stage. Transboundary effects are also to be considered (European Comm ission, 2019).
Significance will vary depending on factors such as magnitude of effects, type, extent, duration, intensity,
timing, probability, cumulative effects and the vulnerability of the habitats and spec ies concerned.
Effects typically considered when assessing significance include the f ollowing:
Direct loss of habitat: a reduction of habitat coverage as a result of physical destruction (i.e. due to its
removal or the placement of construction materials or s ediments); loss of breeding, foraging, resting areas
for species.
Habitat degradation: a deterioration or reduction of habitat quality, e.g. as a result of reduced abundance
of the characteristic species or altered community structure (species compos ition); deterioration of
breeding, foraging, resting areas for species.
Habitat fragmentation: an alteration of distribution patches of relevant habitats and species, e.g. a
contiguous area of habitat split into two or more small, isolated areas, causing a barrier between habitat
Disturbance of species: a change in t he environmental conditions (e.g. noise, frequency of people and
vehicles, increase in suspended sediment or dust deposition); e.g. disturbance m ay cause displacement of
species individuals, changes in species behaviour, mortality risk.
Indirect effects: an indirect change to the quality of the environment (including hydrolog y).
For wind energy developments, typical additional types of effects are the barrier e ffect and the collision risk.
Sources of information to determine the significance of effects may include evidence from similar operations
affecting sites with similar conservation objectives and expert opin ions based on available evidence. However,
the assessment must look at the local circumstances on a site-by-site basis, as what may be significant f or
one site may not be so for another.
The notion of what is ‘significant’ needs to be interpreted objecti vely. The significance of effects should be
determined in relation to the specific features and environm ental conditions of the protected site affected by
the plan or project, taking particular account of the site’s conservation objectives and ecological charact eristics
(European Commission, 2019).
28 Guidance on Wind Energy Developments and EU Nature Legislation
Guidance on Wind Energy Developm ents and EU Nature Legislation
An assessment of significant effects must be based on good science (including best availabl e methods and
knowledge) and reliable da ta, be precautionary and, if appropriate, it should take into acc ount the opinion of
stakeholders, such as NGOs, nature conservation agencies or research ers.
The assessment must apply the principle of proportionality, be compatible with the precautionary principle and
take into account:
the nature, size and complexity of the plan or project;
the expected effects, and
the vulnerability and irreplaceability of the affected EU-protected habitats an d species.
Taking a prop ortionate approach means assessing the significant effects on all the affected EU-protected
habitats and species and effectively avoiding or reducing the effects , while not entailing excessive cost
(Smeeton & George, 2014).
Rulings iss ued by the Court of Justice of the EU have on a number of occasions considered what effects
arising from plans or projects constitute significant effects. In the c ontext of the EIA Directive, it recently (2017)
considered significant effects as potential effects on species which are protected by the Habitats Directive (or
by national law)46.
More detailed information on how to assess significance can be found in Chapters 4.2 (onshore) and 6
(offshore) of this guidance under the specific sub-chapters for habitats an d the different species groups.
3.2 Establishing the content, the area and timeframe of the
assessment (scoping)
Assessments will require the collection of baseline data specific to the context of the individual plan or project.
It is important that a competent national authority for a plan and a developer of a project engage with key
stakeholders to assess the scope of the assessment on the basis of ex pert opinion. The agreed scope should
define which information to include in the assessment in relation to EU -protected habitats and species, Natura
2000 sites, pathways and effects, as well as plans and projects that could act in combination (see Chapter 3.4
on cumulative effects).
It may take over 12 months to establish the baseline conditions for wind energy developments. For example,
to account for variations in factors such as weather conditions and food availability that are known to have a
strong influence on the abundance of highly mobile species such as s eabirds, monthly baseline surveys may
be required for a continuous 24-month period. For seden tary species, or habitats that are not highly dynamic,
baseline surveys over a single 12-month period may be adequate to cover seaso nal variation.
In every case, the timescales for a wind energ y development factor in the need to collect baseline data over a
sufficient period of time, covering seasonal aspects of behaviour (breeding, migration, hibernat ion) as
appropriate. Baseline data should record the environmental conditions i n the scenario that the plan or project
is not implemented, i.e. before any pre-construction or construction activities that would measurably change
the baseline conditions. The plan or project timescale must also take into account the fact that ecol ogical data
may only be valid for a certain period of time and com petent national authorities may only accept the validit y
of data for the purposes of an SEA, EIA or appr opriate assessment if they are collected within a certain time
prior to the assessment47.
46 C-461/17, Holohan and Others, ECLI:EU:C:2018:883, [2018] Reports of Cases (Court Reports general); recalling
judgment of 24 November 2011, Commission v Spain (Alto Sil/Spanish brown bear) and C404/09, EU:C:2011:768,
paragraph 86.
47 The UK bat survey guidelines (Collins, 2016) state that the length of time during which survey data remain valid should
be decided on a case-by-case basis and depends on a number of questions, as follows:
Were the original surveys carried out according to good practice guidelines?
Were the original surveys constrained in any way (in terms of timings, weather conditions, equipment used,
number of surveyors, surveyor expertise, etc.)?
Do the results of the original surveys support the original conclusions and are these still relevant?

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