Framework for Assessing Ecological and Cumulative Effects of Offshore Wind Farms - Part B: Description and Assessment of the Cumulative Effects of Implementing the Roadmap for Offshore Wind Power


Title: Framework for Assessing Ecological and Cumulative Effects of Offshore Wind Farms - Part B: Description and Assessment of the Cumulative Effects of Implementing the Roadmap for Offshore Wind Power
Publication Date:
July 01, 2015
Document Number: 4648
Pages: 24

Document Access

Website: External Link
Attachment: Access File
(670 KB)


Ministry of Economic Affairs (Rijksoverheid) (2015). Framework for Assessing Ecological and Cumulative Effects of Offshore Wind Farms - Part B: Description and Assessment of the Cumulative Effects of Implementing the Roadmap for Offshore Wind Power. Report by Ministry of Economic Affairs and Climate (Rijksoverheid). pp 24.


The nature conservation legislation includes an obligation to assess the cumulative effects of new initiatives with possible adverse effects in combination with other plans and projects. The Framework for Assessing Ecological and Cumulative Effects (FAECE) has been drawn up to determine how to deal with the cumulative ecological effects of the development of offshore wind farms in the southern North Sea. These wind farms are now being rolled out according to the Roadmap for Offshore Wind Power, as included in the letter to the lower house of the Dutch Parliament of 26 September 2014. The scale of these developments in the Netherlands and surrounding countries and their associated ecological risks further underline the need for this assessment framework. Moreover, the measures taken so far to prevent significant adverse cumulative effects based on the precautionary principle are no longer considered to be adequate in the light of the preferred development of offshore wind farms. A suitable method for describing and assessing these cumulative effects was lacking.


Purpose and target audience

The FAECE provides a method based on existing publicly available scientific knowledge and applies it to the Roadmap to identify the cumulative effects, in combination with other developments in the biologically relevant regions, and assess how serious they are. The national policy strategy for offshore wind power (Structuurvisie Windenergie op Zee) and the draft Second National Water Plan (NWP2) prescribe the use of this method for describing and assessing the cumulative effects to support decision-making on the development of offshore wind farms. The FAECE does not apply to location-specific effects.


The FAECE has been prepared in the first instance for use by the government authority responsible for decisions on the development of offshore wind power (such as strategic planning (scoping) documents (structuurvisies) and wind farm site decisions (kavelbesluiten)). This also makes it relevant to consultancies preparing the environmental impact assessments (EIAs) and appropriate assessments (AAs) in support of these decisions and for stakeholders in offshore wind power. The FAECE will be regularly updated to include the latest developments and knowledge.



The FAECE first describes in general terms how cumulative effects can be identified and described. It then focuses on applying this to the development of offshore wind farms, drawing a distinction between a legal and an ecological approach. This is because simply meeting the legal requirements of the Nature Conservation Act (Nbw) will not always adequately protect the ecological values of the North Sea. In some respects, the North Sea requires a different approach. The wildlife of the North Sea comprises a wide variety of species, several of which migrate across the North Sea or over longer distances each year, while the distribution of other species within the North Sea is difficult to predict. National borders are largely irrelevant, but the legislation places considerable importance on area protection and is only applicable within the national territory. For this reason it was decided to assess the effects at the level of the biogeographic regions. This also satisfies the requirements of the nature conservation legislation, although assessments of specific planning decisions, such as EIAs/AAs for wind farm site decisions, must also address location-specific aspects.


The description and assessment of the cumulative effects of a proposed activity take place in a step-by-step procedure. The first two steps are carried out at the same time and are interrelated.

  1. Identify the relevant pressures the envisaged activities could cause.
  2. Identify the habitats and species that may be affected by these pressures.
  3. Describe all other activities that could affect the same species.
  4. Describe the nature and scale of the cumulative effects of all the activities selected in Step 3 on the selected habitats and species.
  5. Evaluate the significance of the effects on the selected habitats and species.
  6. If necessary, adapt the activity by taking measures to prevent the activity causing significant effects.


Calculation of effects

The effects are calculated for those species that are expected to experience significant effects:

  1. Harbour porpoise. The effects of underwater sound have been calculated in a series of steps to identify the numbers of harbour porpoises that will be disturbed and for how many days, and what this means for the population during the implementation period of the Roadmap.
  2. Birds (seabirds, coastal breeding birds and migratory birds). The calculation of cumulative effects on birds took account of collisions with wind turbines in combination with the barrier effect and habitat loss resulting from the presence of wind farms.
  3. Bats. Knowledge of the presence, behaviour and therefore the sensitivity of bats at sea to operational wind farms is still in its infancy. Indicative estimates of collisions have been made based on expert judgements.



The assessment of effects on species is based on the principle that there must be no structural decline in population numbers. If there is, the natural resilience of the population will have been damaged. If recovery is not possible, the species will eventually become extinct or disappear from part of its range. The FAECE assesses bird and bat species against potential biological removal (PBR), a measure of the maximum number of individuals of a species that may be removed from the population in addition to natural mortality and emigration without the population undergoing a structural decline. Population characteristics such as capacity for growth and recovery and the trend in population size are incorporated into this measure. As long as the PBR is not exceeded, there will be no significant – and therefore unacceptable - effects. Effects on the harbour porpoise are assessed against the threshold values in ASCOBANS (Agreement on the Conservation of Small Cetaceans in the Baltic, North-East Atlantic, Irish and North Seas). There is no usable PBR for harbour porpoise because of the type of effect caused by pile driving (disturbance).


Evaluation of the results when applied to the Roadmap

The evaluation of the effects shows that the implementation of the Roadmap could lead to significant effects, particularly on harbour porpoise, lesser black-backed gull, greater black-backed gull, herring gull, Nathusius’s pipistrelle and possibly two other bat species. For the harbour porpoise population, other activities (certainly seismic research and fisheries) are already likely to exert an excessively high pressure on the population. Under the nature conservation legislation, due care should also be given to limiting the number of deaths of migratory birds. This means that additional measures will be needed to provide adequate protection for these birds. Part A of the report mentions measures that can be used.


The FAECE draws no conclusions about the measures to be taken. Decisions on whether measures should be taken and, if so, which ones will be made when the site decisions and any other planning or environmental decisions are made about the development of offshore wind power.

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