Interim Population Consequences of Disturbance

The potential risk of injury and/or disturbance to marine mammals exposed to noise has been identified as a key risk.  Possible consequences of exposure to underwater noise include: disturbance that could cause marine mammals to either move away or change behaviour, suffer temporary hearing damage or permanent physical injury. The interim Population Consequences of Disturbance (iPCoD) model assesses what the longer term and larger scale impacts of these consequences are to the exposed group(s) of animals as a whole.

iPCoD is a protocol for implementing an interim version of the Population Consequences of Disturbance (PCoD) approach for assessing and quantifying the potential consequences for marine mammal populations of any disturbance and/or injury that may result from offshore energy developments.

It has been designed to use the kinds of information that are likely to be provided by developers in their Environmental Statements and Habitats Regulations Assessments. The package is developed for use in R, a free software environment for statistical computing and graphics.

The Interim PCoD framework project was commissioned and jointly funded by The Crown Estate, Marine Scotland Science, the Joint Nature Conservation Committee, The Department for Energy & Climate Change, Natural Resources Wales, Natural England and Scottish Natural Heritage.  Members of each regulatory and statutory nature conservation body, along with developer representatives, participated in a steering committee for the project to ensure that the model met their needs.  The framework is underpinned by a study of The Sensitivity of UK Marine Mammal Populations to Marine Renewables Developments (Harwood & King 2014) that was funded by the Natural Environment Research Council as part of its Marine Renewable Energy Knowledge Exchange programme.

Interim PCoD

This framework has since been used in the UK, Netherlands and Germany. In North America, the interim framework has been developed to explore how it might be used to assess the population level impacts of Navy activities on marine mammals (ONR) and models have been developed to explore the effects of shipping on killer whales (Canada) and Cook Inlet beluga whales (NMFS). Check out the following links to other PCoD projects – PCoD Lite and PCoD+.

The iPCoD version 5.2 code package

The iPCOD version 5.2 code download is available by subscription (below) and contains the model, associated reports and help files.

The model allows the user to predict the population consequences of permanent threshold shifts (PTS) and disturbance on five marine mammal species found in the UK: bottlenose dolphins, harbour porpoise, minke whales, harbour seals and grey seals.

The results of the disturbance expert elicitation have now been processed and are incorporated in version 5 of the code. The key points from the expert elicitation were:

  • For all species the effects of disturbance on vital rates were considered to be lower than estimated in the 2013 elicitation (this is reflected in the new code)
  • In general when comparing species, harbour seals vital rates were thought to be more sensitive to disturbance than grey seals.
  • For both seal species it was expected that disturbance would be most likely to impact on fertility and the survival of the ‘weaned of the year’ animals.
  • Experts agreed that harbour porpoise would be more susceptible to the effects of disturbance than either of the seal species.
  • For harbour porpoise it was expected that disturbance would be most likely to impact on post-weaning calf survival and fertility.

Note: The new disturbance expert elicitation was not conducted for minke whales or bottlenose dolphins, so the effects of disturbance on minke whale and bottlenose dolphin vital rates have remained unchanged since v3.

We emphasise the interim nature of this approach, which was developed to deal with the current situation, where there are limited data on the way in which changes in behaviour and hearing sensitivity may affect the ability of individual marine mammals to survive and to reproduce.

Ongoing development

The iPCoD v5.2 code has been tested under various scenarios, however testing cannot be exhaustive. iPCoD is a freely available, open source programme for which SMRU Consulting rely on user participation to identify bugs and develop version updates. Bug fix/ support requests are necessary for the continued development of this package so please report any issues to All updates will be communicated through the email address provided at subscription.

To download iPCoD, please subscribe to our mailing list below

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Upon completion of your subscription you will be emailed a link to download the iPCoD zip folder.

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SMRU Consulting only support the most recent release of iPCoD, if you require access to any of the previous versions please email us on

Version log


A note from SNCBs

Upon the release of the iPCoD software in 2014, the iPCoD steering group released the following statement on the use of iPCoD:

“The statutory nature conservation bodies (SNCBs) and regulators participated in an Interim PCoD training workshop and are now considering the scope of the tool and how and when it might be used to inform EIA and HRA processes and consenting decisions for marine renewable energy projects. Therefore some of the messages that follow are preliminary.

  1. To date, due to uncertainties about the consequences of disturbance on marine mammal individuals and populations, current consenting decisions have drawn upon expert opinion, but not always in a transparent, comparable and auditable way. Whilst Interim PCoD relies on some strong assumptions and on expert opinion, its strengths include being transparent, auditable and quantitative.
  2. SNCBs consider the Interim PCoD a novel modelling tool with potential to increase our understanding of the effects of disturbance and collision on marine mammal populations, particularly in identifying those input parameters that may most influence the modelled outcomes, and as such support its use.
  3. Developers should consult regulators and their advisers if they are considering using the Interim PCoD at an early stage i.e. before application stage.
  4. Whilst SNCBs do not anticipate a need for the Interim PCoD to be used in the EIA/HRA processes for every single development, this tool may form a useful reference in standardising the type of data submitted in impact assessments which will help when assessing cumulative effects. For large-scale developments and clusters of developments the tool may also help standardise the process for population level assessments. Decisions on when PCoD might be a useful tool should be made on a case-by-case basis in discussion with the relevant SNCBs and Regulators.
  5. One of the main strengths of the Interim PCoD may be at assessing the cumulative effect of several developments and SNCBs advise that this is better achieved at the strategic level (e.g. SEA, and/or as a result of a joint effort between regulators, their advisers and developers [e.g. regional monitoring groups]). We will be working to encourage this approach in the future.
  6. SNCBs acknowledge that there will need to be a process in place to address matters related to the interpretation of model results (e.g. thresholds of acceptable change and time frames).
  7. A joint effort involving government, regulators and industry is now needed to contribute to research on how disturbance influences life-history parameters. The outputs of this research would replace parameters in the model that have been quantified by the expert elicitation process with empirical values. There are some ongoing initiatives through NERC, ORJIP and industry led (e.g. DEPONS) but more is needed.
  8. SNCBs would welcome feedback from developers on where and how they think this tool could add value to assessment processes.”