Pelagic Habitats Thematic Assessment

Cumulative effects assessment for pelagic habitats

It should be noted that the Sankey plots and associated narratives in this thematic assessment are an illustrative representation of a complex set of interactions between DAPSIR components at the coarse North-East Atlantic scale and should be considered and interpreted alongside the supporting full thematic assessment narrative. The Sankey plots should thus be applied with caution and not considered or used as the sole basis for management decisions.

A range of human activities contribute pressures which cumulatively have the potential to affect the state of pelagic habitats and associated ecosystem services (with consequences for societal drivers, e.g., food, energy, space, health, biodiversity). Climate change and ocean acidification, the input of nutrients and organic matter, and changes to hydrological conditions are the predominant pressures. Following a Driver-Activity-Pressure-State-Impact-Response (DAPSIR) framework and a weighting exercise, an indicative assessment of cumulative effects was undertaken (see: CEMP Guideline for details) as a first step to describing potential pathways of cumulative causes and consequences of change in the ecosystem linking these to impacts on ecosystem services. 

The Pelagic Habitats thematic assessment describes the connectivity between the relevant DAPSIR components. Sankey diagrams provide a schematic of potential impact pathways which describes the cumulative causes and consequences of change in the ecosystem, demonstrating that multiple human activities are contributing to multiple pressures, which can lead to multiple impacts on the state of pelagic habitats and associated ecosystem services (see: CEMP Guideline for details). A better understanding of this complexity in the causes and consequences of the cumulative effects from human activities on ecosystem state and ecosystem services is critical in order to explicitly apply the appropriate ecosystem approach to target management measures.

The evidence underpinning the analyses described in this section are drawn from the Driver, Activity, Pressure, State, Impact and Response sections of this thematic assessment and it should therefore be read and interpreted alongside the extended narratives provided therein. The Human activities and Pressures sections of this thematic assessment provide details of the threats that the left-hand side of the Sankey plot (Figure CE.1) poses to pelagic habitats. The State section of this thematic assessment provides details of ecosystem state, shown in the centre of the Sankey plot (Figure CE.1) for pelagic habitats. The right-hand side of Figure CE.1 incorporates the impact on ecosystem service scores in order to present the APSI components of the pelagic habitat ‘ecosystem’ in a single plot. This is consistent with NEAES operational objective S7.O3 on ecosystem services and natural capital, namely to recognise, assess and consistently account for human activities and their consequences in the implementation of ecosystem-based management.

Figure CE.1 shows the complex combinations of human activities and pressures affecting state changes (left-hand side) and the state changes affecting ecosystem services (right-hand side). However, there is currently insufficient understanding and evidence to be able to directly track from left to right, hence the single bar in the centre. This should be a focus of study to inform future assessments. 

Overall, confidence in the evidence for the weighted Bow-tie analysis outputs presented in this Pelagic Habitats thematic assessment is described as medium for evidence and medium for degree of agreement. Additionally, separate confidence assessments have been applied to each module.

Figure CE.1: Impact Potential of Pelagic Habitats under exposure to pressures from human activities in the North-East Atlantic. Columns left to right: Activity, Pressure, State, Environmental Impact, Ecosystem Service. Derived from Exposure score (Extent x Frequency of pressure) x Degree of Impact score (in terms of whether impact is Acute or Chronic). Pressures with a low Degree of Impact score have been removed for clarity. ‘Impact’ in this context does not consider the persistence of the pressure or the resilience of the ecosystem associated with that pressure. If these parameters were included, the relative contribution for some pressures would most likely increase and score higher in the relative ranking. Links are weighted to indicate relative contribution to impact. A wider link = greater potential for impact.

It should be noted that the Sankey plots and associated narratives in this thematic assessment are an illustrative representation of a complex set of interactions between DAPSIR components at the coarse North-East Atlantic scale and should be considered and interpreted alongside the supporting full thematic assessment narrative. The Sankey plots should thus be applied with caution and not considered or used as the sole basis for management decisions.
 

Figure CE.1 demonstrates the complex relationships which the collective pressures from human activities have on the quality status of pelagic habitats. This complexity suggests that while single-issue responses may be effective, in order to fully apply ecosystem-based management OSPAR needs to consider the causes and consequences of changes in ecosystem state more holistically, and thus: 

• recognise that any measures to reduce impacts, while critical to ecosystem health, could have potential consequences for our ability to maintain ecosystem services to meet society’s needs, which in turn has consequences for the viability of human activities in the North-East Atlantic;
• recognise that pressures may have additive, multiplicative, synergistic or antagonistic interactions when combined, which has implications for the nature of the threats posed to pelagic habitats and how best to manage those threats.

Methodology

(See: CEMP Guideline: Cumulative effects assessment for the QSR 2023 (Bow Tie Analysis))

A modified Bow-tie Analysis (Cormier et al., 2018; Cormier et al., 2019) was developed to identify and connect all the DAPSIR components, integrating these into either a pressure (e.g., underwater sound, litter, hazardous substances, eutrophication) or a biodiversity receptor- focused analysis of the causes and consequences of change (e.g., pelagic habitats, benthic habitats, fish, marine birds, marine mammals). For the biodiversity assessments, the APS connections are weighted to determine which are the most important, using an adaptation of the ODEMM pressure assessment (Robinson et al., 2013; Knights et al., 2015) focusing on:

1. Exposure module: spatial extent and frequency for all activity pressure combinations on state, to generate exposure weightings;
2. Impact potential module: spatial extent, frequency of occurrence and impact potential for all activity pressure combinations on state, to generate impact potential weightings;
3. Risk module: spatial extent, frequency of occurrence, impact potential for all activity pressure combinations on state, combined with pressure persistence and ecosystem resilience, to generate risk weightings.

The SI (ecosystem services) connections are weighted to determine the most important (Cornaccia, 2022).

The impact potential and ecosystem services outputs are combined and presented in Sankey diagrams (Figure CE.1).

Confidence in this weightings exercise for pelagic habitats was assessed according to the QSR 2023 Guidance. Confidence is based on two criteria to communicate the degree of uncertainty in the key findings: (i) level of evidence (determined by considering the type, amount, quality, and consistency of evidence (i.e., Robust, Medium, or Limited)), and (ii) degree of agreement (i.e., High, Medium, or Low).

Exposure module:

Confidence Assessment: Evidence – Medium; Consensus – Medium

The assessments for this QSR have demonstrated that pressures from human activities are widely distributed in the OSPAR Maritime Area. The presence of pressures does not automatically lead to adverse impacts.  However, in the first instance, consideration of the spatial and temporal extents of pressures provides a useful basis for our consideration of cumulative effects within a risk-based approach (in line with the NEAES principle and strategic approach). 

The exposure module describes the extent of the pressure from human activities in the North-East Atlantic. It considers the spatial extent and frequency of human activity / pressure combinations which have been identified as important for pelagic habitats (derived from spatial extent score multiplied by frequency score). Exposure only relates to the pressure cell in the DAPSIR schema. Consideration of exposure in isolation provides a coarse cross-cutting assessment to provide early identification, which allows OSPAR to develop management strategies for pressures to prevent or minimise impacts. 

The thematic assessments for Eutrophication and Climate Change Thematic Assessment and the Ocean Acidification Other Assessment describe the pressures on pelagic habitats. The Radioactive Substances Thematic Assessment identifies inputs of radionuclides from a range of human activities but has concluded that their current levels do not exert significant radiological impacts on biodiversity.

Climate Change and ocean acidification pressures, inputs of nutrients and organic matter, input of radionuclides and changes to hydrological conditions have some of the highest exposure scores, demonstrating the ubiquitous nature of some of these pressures in the North-East Atlantic. Changes to hydrological conditions also rank highly.

The exposure scores support the importance that OSPAR places on these pressures in the North-East Atlantic Environment Strategy:

• Strategic Objective 1 to tackle eutrophication through limiting inputs of nutrients and organic matter, and the work of the Hazardous Substances and Eutrophication Committee ( Eutrophication Thematic Assessment ).
• Strategic Objective 3 to prevent pollution by radioactive substances, and the work of the Radioactive Substances Committee ( Radioactive Substances Committee Thematic Assessment ). 
• Strategic Objective 9 to safeguard the structure and functions of the seabed/marine ecosystems by preventing significant habitat loss. 
• Strategic Objectives 10 to raise awareness of climate change and ocean acidification; 11 to facilitate adaptation to the impacts of climate change and ocean acidification; and 12 to mitigate climate change and ocean acidification ( Climate Change Thematic Assessment , Ocean Acidification – Other Assessment).

Multiple human activities have been identified as exerting these pressures in the North-East Atlantic. Any actions to manage these pressures so as to prevent or reduce impacts on state, either individually or cumulatively (collectively), will need to consider if and how these human activities might best be targeted (and the consequences for the associated drivers and ecosystem services) within an Ecosystem Approach.

Impact potential module

Confidence Assessment: Evidence – Medium; Consensus – High

The impact potential is incorporated with the exposure module (spatial extent and frequency) of pressures from specified human activities (derived from the aggregated exposure score multiplied by the degree of impact score). Impact potential here relates to the generic interaction in terms of the likely effects of a pressure on the ecological component, in the following categories: low potential for significant impact, chronic impact or acute impact (Robinson et al., 2013). Figure CE.1 shows the combined weighted scores for exposure and impact potential. 

Following discussions with the expert groups, activity-pressure combinations with a low potential impact score based on the current available evidence were filtered out. Thus, the input of radionuclides has been filtered out based on the conclusions in the Radioactive Substances Committee Thematic Assessment , as these have been demonstrated to have low potential for significant impact. Other pressures filtered out as having low potential for significant impact are extraction of, or mortality/injury to, wild species from fishing activities.

The relative ranking of pressures changes when impact is considered. Climate change and ocean acidification pressures rank highly (see the Climate Change Thematic Assessment for detail on contributing human activities). Input of nutrients, input of organic matter and changes to hydrological conditions also rank highly.

Risk module

Confidence Assessment: Evidence – Low; Consensus – Low

Given their low confidence scoring, the outputs from the risk analyses have not been included in this thematic assessment for QSR 2023. Details of the criteria applied in the risk module are described in the CEMP Guideline.

Regional Summary of likely cumulative effects

Confidence Assessment: Evidence – High; Consensus – Medium

While the weighted Bow-tie analyses displayed in the Sankey diagrams have been produced at the North-East Atlantic scale, consideration can also be given to where regional differences may arise, by cross-referencing other assessments in the QSR 2023.

The Pelagic Habitats thematic assessment identifies the cumulative pressures for pelagic habitats (but no regional breakdown of pressures is attempted there) in terms of both exposure and impact :

The list below summarises the main pressures impacting pelagic habitats, with information on associated activities. Please note that activity-pressure combinations scored as having a low degree of impact based on the current available evidence were filtered out from the relevant Sankey diagram; the activity-pressure links listed below relate to the unfiltered outputs used in the Exposure assessment. The climate change pressures are increased sea temperatures, open ocean stratification, acidification, changes in nutrients and changes in upwelling intensity.

• Input of nutrients from agriculture; aquaculture; restructuring of seabed morphology; waste water treatment and disposal; and industrial uses; 
• Changes in hydrological conditions from coastal defence and flood protection; offshore structures; extraction of oil and gas; renewable energy generation;
• Input of other substances (including chemical contaminants and radionuclides) from industrial uses; extraction of oil and gas; military operations; non-renewable energy generation (Nuclear); research, survey and educational activities; and urban uses.
• Extraction of, or mortality/injury to wild species from fish and shellfish harvesting;
• Input of NIS from transport – shipping.

While OSPAR does not have evidence for all human activities, the regional breakdown of relative intensities of activities, namely agriculture; aquaculture; oil and gas; nuclear; renewable energy; fisheries and shipping, has been extracted from the supporting evidence for the QSR 2023 and is summarised below.  The direct influence of the cumulative pressures from these activities on pelagic habitats is likely to follow similar trends in intensity within these regions. Although pressures spread beyond the spatial extents of the human activities, insufficient evidence is currently available, and so trends in indirect cumulative pressures have not been considered.

The Human Activities Thematic Assessment describes:

• low relative intensity of agriculture sector activity in Arctic Waters (Region I) and Wider Atlantic (Region V);
• moderate relative intensity of agriculture sector activity in Celtic Seas (Region III) and Bay of Biscay and Iberian Coast (Region IV);
• high relative intensity of agriculture sector activity in Greater North Sea (Region II);
• moderate relative intensity of aquaculture sector activity in Celtic Seas (Region III) and Bay of Biscay and Iberian Coast (Region IV);
• high relative intensity of aquaculture sector activity in Arctic Waters (Region I) and Greater North Sea (Region II);
• low relative intensity of fisheries sector activity in Wider Atlantic (Region V);
• moderate relative intensity of fisheries sector activity in Bay of Biscay and Iberian Coast (Region IV);
• high relative intensity of fisheries sector activity in Arctic Waters (Region I), Greater North Sea (Region II) and Celtic Seas (Region III);
• low relative intensity of offshore renewable energy sector activity in Bay of Biscay and Iberian Coast (Region IV);
• moderate relative intensity of offshore renewable energy sector activity in Celtic Seas (Region III);
• high relative intensity of offshore renewable energy sector activity in Greater North Sea (Region II);
• low relative intensity of transport and shipping sector activity in Wider Atlantic (Region V);
• moderate relative intensity of transport and shipping sector activity in Arctic Waters (Region I); and
• high relative intensity of transport and shipping sector activity in Greater North Sea (Region II), Celtic Seas (Region III) and Bay of Biscay and Iberian Coast (Region IV).

The Offshore Industry Thematic Assessment describes:

• low relative intensity of oil and gas sector activity in the Bay of Biscay and Iberian Coast (Region IV) and Wider Atlantic (Region V);
• moderate relative intensity of oil and gas sector of activity in Arctic Waters (Region I) and Celtic Seas (Region III); and
• high relative intensity of oil and gas sector activity in Greater North Sea (Region II).

The Radioactive Substances Committee Thematic Assessment describes:

• no nuclear sector activity in Wider Atlantic (Region V);
• low relative intensity of nuclear sector activity in Arctic Waters (Region I);
• moderate relative intensity of nuclear sector activity in Bay of Biscay and Iberian Coast (Region IV); and
• high relative intensity of nuclear sector activity in Greater North Sea (Region II) and Celtic Seas (Region III).

Regional evidence for trends in the intensity of other human activities and climate change and ocean acidification was not available in sufficient detail to be utilised in this assessment.