This section, based on work reviewed by the UK Marine Monitoring and Assessment Strategy (UKMMAS) Productive Seas Evidence group (PSEG), presents the approach to cumulative effects assessment of activities in the marine environment and how this relates to the achievement of Good Environmental Status.


Progress since 2012

The UK Marine Strategy Part 1 in 2012 (HM Government, 2012) noted that improving the evaluation of the cumulative effects of human activities on marine ecosystems was an important priority to ensure that the management decisions needed to protect our seas are supported by the best possible evidence. 

The UK has subsequently done a significant amount of work in this area both

  • nationally initially through the Cross-Government working group on Cumulative Effects Assessment and currently in Productive Seas Evidence Group (PSEG),
  • and through leading the OSPAR Group on Cumulative Effects, which is looking at this from the perspective of the North East Atlantic for the Quality Status Report 2023.  

The Centre for Environment Fisheries and Aquaculture Science (Cefas) has been commissioned to develop a cumulative effects assessment methodology, which applies the ecosystem approach utilising the risk analysis tool Bow Tie Analysis. 

An ecosystem-based approach to cumulative effects assessment

The method has been developed to practically apply the ecosystem approach: “the comprehensive integrated management of human activities based on the best available scientific knowledge about the ecosystem and its dynamics, in order to identify and take action on influences which are critical to the health of marine ecosystems, thereby achieving sustainable use of ecosystem goods and services and maintenance of ecosystem integrity” (OPSAR and HELCOM, 2003).

The approach we are taking considers the indicators as ecosystem components within the assessment of cumulative effects. It builds on outputs from the individual ecosystem component and descriptor assessments by further investigating the threats in order to achieve the targets related to each indicator (and the consequences associated with the status), and also the contribution that current management of these threats and consequences make to the nature and scale of the cumulative effects.

We have considered the individual indicators as integral components of the ecosystem (including both pressure and biodiversity indicators) and the relationships between these ecosystem components. Applying this, systems thinking allows us to frame our cumulative effects assessment on how the constituent parts of the ecosystem interrelate (and how they work in time and space). As humans are part of the ecosystem, it also provides a platform for us to consider environmental, social and economic relationships together. Applying this holistic approach allows us to make informed choices on the state of the marine environment and how it changes in response to the cumulative effects from multiple human activities in the context of current management regimes.

The simple premise behind this approach is that a range of human activities cumulatively exert pressures on the marine environment to cause changes and the environment responds to these changes (Figure 1). By understanding these relationships, we can better determine the significance of these complex changes in the context of Good Environmental Status (GES).

Figure 1. Mechanisms for human activities to change ecosystem state (GES)

We have used an adapted risk analysis methodology to undertake our assessments of cumulative impacts (the ISO Standard: Bow Tie Analysis). The Bow Tie Analysis is a simple diagrammatic way of describing and analysing the pathways of an environmental risk from causes (i.e. marine activities and the pressures they exert), which contribute to a loss of control (e.g. environmental status represented by an indicator) through to consequences (e.g. environmental impacts), factoring in the effectiveness of any controls (management measures) that may exist. Environmental indicators are commonly used as a representative proxy of the wider ecosystem and linking different Bow Tie Analyses together allows us to consider multiple causes and consequences.

Diagrammatically, the loss of control (e.g. the aspect of environmental status that the indicator describes) is represented by the knot of the bow-tie, the causal factors listed to the left and the environmental outcomes listed to the right (Figure 2). There are two sets of management measures: preventative controls (which aim to stop a potential cause triggering a change) and mitigation controls (which aim to reduce the impact of a change if it does occur).

Figure 2. Example Bow Tie Analysis constructed around OSPAR pressure or state indicators

Using the example of seafloor damage (the knot), examples of possible causes from the Bow Tie Analysis are aggregate extraction, fishing, infrastructure construction or navigational dredging. Possible consequences may be changes to ecosystem goods and services, changes in biodiversity, or a reduced economic capacity if navigation channels are not maintained. This assesses cumulative effects around a single issue (i.e. the multiple causes and impacts associated with seafloor damage).

The relationships between the ecosystem components are further investigated by chaining associated Bow Tie Analyses together. This builds a picture of the collective pressures arising from human activities without losing sight of the causal factors and any management measures we already apply. In the example below (Figure 3), we have linked PBDE’s from flame retardants in seabed sediment to PDBE’s in biota through to the breeding success of seabirds and then to abundance in seabirds overall. Without our assessment these would have been independent indicators, which each contain multiple pressures and receptors. However, we have used these four indicators, which on their own are reasonably complex and used Bow Tie to analyse them cumulatively to think through the ultimate consequences of a range of cause effect pathways. This allows us to answer specific questions on the status of the environment.

Figure 3. Example of Bow Tie Analysis linking contaminant pressures in seabed to seabirds

Outstanding issues / Going forward

The current focus in the development of the Bow Tie methodology is to develop specific case studies to practically evaluate the interaction of multiple pressures in real world scenarios. Appropriate management measures can then be put in place lead by the UK detailed assessments will be undertaken in 2019-2021. This work commenced in Autumn 2018 with an OSPAR workshop. 

More detail on applying risk assessment principles to cumulative effects assessment can be found in the OSPAR ecosystem assessment outlook (OSPAR Commission, 2017)


HM Government (2012) ‘Marine Strategy Part One: UK Initial Assessment and Good Environmental Status’ (viewed on 5 July 2018)

OSPAR and HELCOM (2003) “Statement towards an Ecosystem Approach to the Management of Human Activitiesadopted by the Joint Ministerial Meeting of the HELCOM and OSPAR Commissions held in 2003 in Bremen (Germany)  (viewed on 10 January 2019)

OSPAR Commission (2017) ‘Intermediate Assessment 2017’ (viewed on 21 September 2018)