Benthic Habitats Thematic Assessment

Executive Summary

Benthic habitats and the integrity of the seafloor

Many benthic habitats within the OSPAR Maritime Area are under threat from various pressures (see: Table S.2 in the State chapter). These include physical disturbance, modification of substrate or loss (such as abrasion by bottom trawling, sediment extraction or man-made structures) and chemical (by nutrients enrichment or contaminants) and biological impacts (e.g., spread of non-indigenous species or native species exploitation). Their impact is not uniform, and thus the state of benthic habitats and the level of threat varies across the OSPAR Regions. The indicators, data and methodology that support this thematic assessment also differ across the OSPAR Regions. The results of this thematic assessment should therefore be considered on Region by Region and cannot be directly compared.

This assessment, both for broad-scale habitats and those identified as threatened and declining, shows that (see: Table S.2 in the State chapter) many are in poor status, although some areas also show good status for a specific pressure and impact (eutrophication). All but one of the eighteen benthic habitats that OSPAR has identified as threatened and/or declining show no signs of improvement in the regions where they occur. Some habitats (e.g., oyster beds and seagrass beds) also show a decrease in distribution and extent in some Regions.

In those areas where the OSPAR Common Indicators were applied, physical disturbance remains the main pressure contributing to widespread reduction in diversity and changes in sensitive benthic communities. The Common Indicators assessing physical disturbance to the seabed by bottom trawling (BH3a) and changes to sensitive species (BH1) showed that most benthic habitats in areas where such fishing activities take place are under significant threat or impact. The diversity of benthic communities (BH2b) is particularly poor in inshore habitats of the Greater North Sea Region (the only one assessed with this indicator). Coastal waters show mainly high/good status for benthic vegetation and invertebrates with regard to eutrophication, but this remains an issue in the eastern part of the Greater North Sea, including Kattegat, and the Channel (BH2a). However, in the Arctic Waters Region climatic factors are the most significant variables driving the trends detected in benthic habitats. 

In the face of climate change and ocean acidification, as well as increasing production of food and energy there is more than ever an urgent need to lower the pressures on benthic habitats. This can be achieved through a combination of responses including effective area-based management, sustainable use and other regulation of human activities and innovations. Where they are assessed, i.e., in the Greater North Sea, Celtic Seas, Bay of Biscay and Iberian Coast, benthic habitats are already impacted by human activities.

It is difficult to assess the effectiveness of measures to improve the status of benthic habitats, due to the multiple activities and pressures involved. In addition, the effects of measures on the recovery of habitats may take a long time to become evident. However, the lack of clear signs of improvement reported here suggests that current measures have been inadequate or ineffective. 

This assessment provides an evidence base to help develop future response measures, for example targeted action plans. These need to be supported by improved monitoring and access to data alongside better resolution and geographic coverage in the next iteration of assessments and measures.

Q1. Identify the problems? Are they the same in all OSPAR regions?

Benthic habitats and the integrity of the seafloor are under pressure from physical, biological and chemical stressors. These arise from human activities driven by society’s need for food, health and wellbeing, recreation, energy, materials, communication, and trade. This means that tackling problems resulting from these anthropogenic pressures is a multi-faceted challenge involving many aspects of our society.

OSPAR has a vision of a clean, healthy and biologically diverse North-East Atlantic Ocean which is productive, used sustainably and resilient to climate change and ocean acidification. Fisheries are an important activity in the OSPAR Maritime Area that contributes to societies’ need for food and should be managed to ensure sustainable use. However, fishing impacts the ecosystem and its food webs and, even when considered sustainable, will leave a "footprint".  

The physical disturbance caused by bottom-contacting fishing gear was shown to persist as the main pressure causing a widespread reduction in biodiversity and changes to the sensitive benthic communities in the areas of the OSPAR Maritime Area that were assessed (see: Table S.2 in the State section).

The Quality Status Report 2010 (QSR 2010) identified damage to benthic habitats resulting from fishing activity as a key issue. Protection of benthic habitats from disturbance, including from future pressures such as deep-sea mining, was seen as a challenge, one further exacerbated by limited knowledge of deep-sea ecological functioning, data paucity for those habitats and limited biodiversity conservation measures and actions. QSR 2023 acknowledges that the state of benthic habitats, and thus the need to develop and implement protective measures, varies across OSPAR Regions. This variation was also observed in OSPAR’s 2017 Intermediate Assessment. It did not report trends, being the first quantitative assessment of benthic indicators for which data and resources were available but identified physical disturbance as the main pressure in the Greater North Sea, Celtic Seas and Bay of Biscay and Iberian Coast.

Benthic habitats are also very sensitive to the effects of climate change, particularly those that are already exposed to multiple anthropogenic pressures. Sensitivity to climate-driven pressure is directly influenced by the species and associated biological communities that characterise the habitat (see: Table CC.2). Increases in temperature (and marine heat waves), lowered and/or increased variability of pH (and altered carbonate or nutrient cycle chemistries), variations in salinity, sea-level rise and storminess are the main current and projected threats to benthic habitats. This is anticipated in general for most of the broad habitat types, with exacerbated effects near the coast, but also for threatened biogenic habitats such as cold-water corals, maerl beds, Modiolus beds, Zostera beds and kelp forests.

Q2. What has been done?

OSPAR has identified eighteen habitats considered to be of concern in the coastal, shelf and deep waters of the North-East Atlantic. Recommendations for actions to be taken by Contracting Parties nationally and collectively to protect and conserve these habitats have been adopted. These recommendations are broad in nature and address a range of human activities and pressures. They include:

• steps to report appropriate national legislation for the protection of a given habitat;
• consideration of how to strengthen the knowledge base, monitoring and assessment;
• steps to manage key human activities;
• a call for the designation of Marine Protected Areas (MPAs) and cooperation with relevant competent organisations to address key activities (such as fishing and shipping).

Current measures being taken by OSPAR and other competent bodies to support improvement in the state of benthic habitats focus in particular on fisheries extraction, eutrophication, mineral extraction near to shore, dredging, oil and gas extraction and cable placement.

The OSPAR Network of Marine Protected Areas is an important response for improving the status of benthic habitats, including, but not limited to, those habitats identified in the OSPAR List of threatened and/or declining species and habitats. This network is progressing according to regional and global targets in some OSPAR Regions, under a commitment to fill gaps, expand the network to include other effective area-based conservation measures (OECMs) and cover at least 30% of the OSPAR Maritime Area by 2030. Some habitats such as Cymodocea meadows are naturally region-specific, and others, like carbonate mounds, are not sufficiently known or included, making an assessment of the ecological coherence of the MPA network challenging.

The Collective Arrangement has proved to be a useful framework for facilitating cooperation with other competent authorities on the management of human activities that can affect benthic habitats but lie outside the competence of OSPAR. One example is the fishery closures and restrictions adopted by the North-East Atlantic Fisheries Commission (NEAFC) to protect vulnerable benthic habitats in some areas beyond national jurisdiction.

Q3. Did it work?

There are few indications at this stage that the existing measures and their current levels of implementation will be sufficient to improve the status of the assessed benthic habitats (see: Table S.2 in the State chapter).

Despite recent progress, the current limitations in terms of available data and agreed methods mean that it is still a complex matter to assess precisely whether current measures are either able or sufficient to reduce the pressures and human activities that continue to affect the state of benthic habitats in the North-East Atlantic. 

This largely relates to how the measures have been designed and are reported. Several measures have been developed to address several activities and related pressures. Due to the complex interactions within the marine environment, improvements to benthic habitats based on measures taken now are difficult to estimate and may not be recorded until a long time after implementation. Some measures, such as closing areas for specific activities or designating and managing MPAs, are being implemented, at least partly, but only for limited areas and habitat types, and years of relevant monitoring and policy controls will be needed to assess their effectiveness. Unless reporting is very explicit it is not easy, or in many cases even possible, to identify which measure specifically addresses which activity or pressure, especially in the context of climate change and ocean acidification, and because the same action may also be reported as a response to multiple measures. This emphasises the need to apply the precautionary principle, one of the guiding principles for the implementation of the OSPAR Convention.

Q4. How does this field affect the overall quality status?

The current assessment reports several continuous and wide-scale pressures from human activities affecting most benthic habitat types at various intensities in the areas where OSPAR Common Indicators have been applied (see: Table S.2 in the State chapter). The OSPAR listed threatened and /or declining habitats (such as Lophelia reefs or Zostera beds) are typically either stable or declining, and in poor quality status, in all OSPAR Regions. For the Arctic Waters Region there is limited historical data available on benthic habitat distribution and condition, but baseline information is available (for example on megabenthos species larger than 1 cm) for use in future work.

It is not possible to evaluate changes in benthic habitats against the outcomes of QSR 2010, as common quantitative benthic indicators were not available at that time and have been developed subsequently. Common Indicator Assessments have been undertaken by EU member states for each broad-scale habitat type under the European Union Marine Strategy Framework Directive (EU MSFD) in the Greater North Sea, the Celtic Seas and the Bay of Biscay and Iberian Coast, where data monitoring and other ad hoc data sources were made available. The coastal habitats in all those Regions have been assessed as generally in good biological status, although it was noted that local areas negatively impacted by nutrient and organic pollution were also found and that there were still several areas with unassessed water bodies. Physical disturbance remains the main pressure contributing to widespread biodiversity loss in the benthic communities, with details varying according to the data available or the indicator chosen: decreased biodiversity in the coastal habitats of the Greater North Sea, and significant changes to typical species composition in the Bay of Biscay and Iberian Coast.

Q5. What do we do next?

In the North-East Atlantic Environment Strategy (NEAES) 2020-2030 (OSPAR NEAES) (see: Response section). OSPAR acknowledges the consensus among scientists that the health of the North-East Atlantic is at risk and that urgent action is needed to address the loss of biodiversity and improve ecosystem functioning.

Within NEAES 2030, OSPAR expresses its ambition to conserve marine biodiversity and ecosystems in order to achieve good status of benthic habitats (Strategic Objective 5; S5), to restore degraded benthic habitats so as to increase their resilience to climate change and ocean acidification (S6), to ensure sustainable use of the marine environment, in particular with a view to assessing the effects and addressing cumulative impacts (S7), and to prevent significant loss and disturbance of benthic habitats (S9). OSPAR has committed to regional coordination and to facilitating the implementation of the EU MSFD, by developing compatible standards and assessments for those Contracting Parties that are also EU member states (Sx), and to applying an ecosystem-based management approach in coordination with fishery management bodies and other competent organisations.

The Strategic Objectives (S) in the NEAES are to be achieved through Operational Objectives (O), as follows:

• expand the MPA network including OECMs to cover at least 30% of the OSPAR Maritime Area (S5.O1), improve MPA management (S5.O2 and 3, S11.O2) and increase the relevant ecosystems’ resilience to climate change and ocean acidification (S11.O1);
• implement agreed measures that allow threatened and declining benthic habitats to recover (S5.O5);
• revise the list of threatened and declining benthic habitats to consider climate change and ocean acidification impacts (S11.O3);
• reduce pressure on benthic habitats to allow them to achieve good environmental status (S5.O4);
• identify benthic habitats that are suitable for restoration and develop and implement a regional approach to achieve restoration (S6.O1 and 2);
• (further) develop methods to analyse cumulative impacts on benthic habitats and use the resulting knowledge to reduce and/or prevent the severity of cumulative pressures on benthic habitats (S7.O1 and 2); develop an evidence base to reduce and prevent direct benthic habitat loss and disturbance due to human activities (S9.O1);
• support the development of common principles and guidance to promote and facilitate the sustainable development of benthic habitats, with particular attention to the scaling-up of offshore renewable energy, minimised cumulative environmental impacts (S12.04) and the development of nature-based solutions to promote the sequestration of nutrients in benthic systems (S12.01).

The effective implementation of many of these objectives will mainly depend on national actions. These should continue to be reported through, for example, the implementation of the recommendations on listed threatened and declining species and habitats. 

OSPAR recognises the need to increase its focus on identifying and implementing collective actions which add value both to existing national actions and to the efforts of other international organisations. Many of the current actions focus only on monitoring and assessment and relatively few on response, and in either case there has been only modest progress, as seen in the biodiversity thematic assessments of the QSR 2023. Although there is a good level of engagement in implementing national actions under the recommendations, the level of engagement in collective actions is clearly at a lower level, with some of the more challenging actions not having been progressed and implemented. OSPAR will therefore have to develop a series of biodiversity action plans which comprehensively address all benthic habitats exposed to anthropogenic pressures, in order to identify effective high-priority response measures.

This assessment provides a major evidence-based tool for developing clearly defined and targeted action plans and responses. OSPAR will have to strengthen its resources and capacity to use this evidence base and all future assessments in order to support engagement with its Contracting Parties and other international partners. The development of a practical approach to ecosystem-based management should provide the opportunity and the mechanism to share evidence and common objectives to ensure more sustainable use of the marine environment. 
Progress made against all these challenging biodiversity objectives will be evaluated through future OSPAR assessments of the health of the North-East Atlantic, driven by the successful implementation of the NEAES and its strategic and operational objectives.

A review currently planned for 2025 should provide an opportunity to adjust the NEAES and, if necessary, take further action to protect and conserve marine biodiversity. The review should include the risks of large-scale ecosystem impacts arising from future offshore renewable energy developments.

Benthic Habitats Assessments

Contributors

Lead authors: Paul Coleman, Emily Corcoran, Irusta Gonzalez, Manuel José, Laurent Guerin (assessment co-lead), Adrian Judd, Anna Lizińska, Stefano Marra, Liam Matear, Maider Plaza, Petra Schmitt, Gro van der Meeren, Cristina Vina-Herbon (assessment co-lead), Sander Wijnhoven, Daniel Wood

Supporting authors: Mats Blomqvist, Pål Buhl-Mortensen, Axel Kreutle, Janos Hennicke, Neve McCann, Giacomo Montereale Gavazzi, Nina Schröder, Gert Van Hoey, Thorsten Werner

Contributing authors: Lena Avellan, Federico Cornacchia, Catherine Kronin

Supported by: OSPAR Commission Secretariat, Biodiversity Committee (BDC), Intersessional Correspondance Group on the Quality Status Report (ICG-QSR), Intersessional Correspondance Group on Ecosystem Assessment Outlook (ICG-EcoC), Intersessional Correspondance Group on Economic and Social Analysis (ICG-ESA), Climate Change Expert Group (CCEG), Intersessional Correspondance Group on Marine Protected Areas (ICG-MPA), Intersessional Correspondance Group on Protection and Conservation of Species and Habitats (ICG-POSH), Intersessional Correspondance Group on the Coordination of Biodiversity Assessment and Monitoring (OCG-COBAM), Biodiversity Thematic Assessment Drafting Group (BiTA).

Delivered by

This work was co-funded by the European Maritime and Fisheries Fund through the project: “North-east Atlantic project on biodiversity and eutrophication assessment integration and creation of effective measures (NEA PANACEA)”, financed by the European Union’s DG ENV/MSFD 2020, under agreement No. 110661/2020/839628/SUB/ENV.C.2.

Citation

OSPAR, 2023. Benthic Habitats Thematic Assessment. In: OSPAR, 2023: Quality Status Report 2023. OSPAR Commission, London. Available at: https://oap.ospar.org/en/ospar-assessments/quality-status-reports/qsr-2023/thematic-assessments/benthic-habitats/