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Protecting the ocean through marine net gain

14 February 2024

Recent research undertaken by Plymouth Marine Laboratory scientists has revealed several key insights from offshore windfarm stakeholders, in relation to the development of marine net gain policy and implementation.
Pete Godfrey | Unsplash

What is Marine Net Gain?

Broadly speaking, marine net gain (MNG) is a concept that aims to put the marine environment into recovery and prioritise activities that will leave the marine environment in a measurably better state than it was previously.

Jonathan Burney, Director of Marine Strategy and Government Advice with Natural England, described MNG as an “exciting, emerging area of marine policy that offers opportunity to accelerate marine nature recovery in English waters”.

The newly developed concept of net gain has been used by many countries in recent years but mainly for terrestrial activities. For the marine realm, there is little consensus on how MNG can provide optimal environmental and societal outcomes from marine activities, such as offshore windfarm construction, operation and decommissioning.

This study sought to clarify the key issues that need to be addressed for effective MNG implementation, focusing on the rapidly expanding offshore windfarm sector. Study participants were drawn from the UK's offshore windfarm community and explored a range of aspects of MNG policy formulation, implementation, delivery and regulation.

Andrew Edwards-Jones, lead author on the paper and Social Scientist at PML, commented:

“Marine Net Gain (MNG) is a new policy area for the UK, and offers genuine opportunity to deliver marine nature recovery through industry involvement. The perceptions of MNG from offshore wind stakeholders therefore offers useful inputs into current policy development."

"Our analysis revealed that restoring shellfish/mussel beds and actions supporting invertebrates and plankton were perceived as the most important net gain actions, reflecting stakeholder awareness of the role these communities play in underpinning higher trophic level biodiversity and functioning. Fishing was viewed as the most significant pressure to prioritise when developing strategic net gain and our stakeholders supported adoption of a broad ‘environmental net gain’ approach to development that includes the social, environmental and economic value of natural assets in addition to enhanced biodiversity. The results of this study reinforce the potential now being seen across Europe’s offshore wind industry to set up wind farms to be much more nature-inclusive”.
Study highlights

Over 80% of participants indicated that certain external inputs, including information for climate change adaptation options and habitat mapping data, were important to enable delivery of MNG.

The most important ecosystem services to include within MNG measures were perceived as those relating to fisheries, maintaining nursery habitats and climate regulation.

Over 75 % of stakeholders thought that fish, birds and marine mammals should be included within MNG targets.

Stakeholders felt the most important MNG actions for environmental restoration/enhancement of future offshore wind deployment were shellfish/mussel bed, invertebrate habitat restoration and actions supporting plankton communities.

Stakeholders agreed (83%) that MNG actions should be considered at the decommissioning stage, and that, contrary to prevailing opinion, the preferred decommissioning option was the complete removal, followed by abandonment, of all structures. It was also noted that when structures had been designed to be left as a reef, then it would be acceptable to partially remove or topple them.

Stakeholders felt that strategic MNG assessments should prioritize fishing pressures and those arising from physical structures, including cables.

Aquaculture farming was deemed most feasible to co-exist with fixed offshore wind farms, while floating wind farms were felt to be more co-locatable with fishing practices and carbon capture storage devices compared to fixed structures.
Study recommendations

Recommendations suggested for future policy development and scientific research in relation to the application of MNG assessment for offshore wind farm projects include:
  • Increased understanding of MNG concepts
    • Opportunities for meaningful stakeholder engagement should be available to help clarify terminology and share knowledge across different sectors.
    • Explore the most useful formats and data transfer mechanisms for the provision of specific information needs required for effective ENG assessments, such as adaptive policy guidelines, spatial habitat data and biodiversity data.
    • Provide guidance to stakeholders of development-specific risks of external pressures as well as on the restoration potential for specific habitats likely to be impacted by proposals.
  • MNG to measure impacts on habitats and species
    • Include coastal and offsite impacts in MNG assessments, incorporating marine mammals, birds, invertebrates and irreplaceable habitats, such as corals.
  • MNG to incorporate environmental benefits
    • Include the social, environmental and economic value of natural assets where these extra benefits are underpinned by biodiversity.
  • Include priority ecosystem services in MNG measures
    • Specify ecosystem services on which to focus: fisheries, maintaining nursery habitats, and climate regulation.
    • Increase understanding of cultural ecosystems services among stakeholders, with guidance on their definition, assessment and valuation as part of MNG.
  • Develop metrics for MNG
    • Develop a new Net Gain metric that is nuanced for a marine context, as preferred by offshore energy stakeholders.
    • A secondary option is to rely on an industry levy for a strategic fund.
  • Prioritise pressure reduction actions for MNG
    • Include pressure reductions recommendations, which can have an important role to play in successful MNG strategies.
    • Reduce impacts from some fishing methods and the disturbance effects of the physical structures (including cables), which were of high priority for consideration within strategic MNG assessments for offshore windfarms.
  • MNG to incentivise active restoration measures
    • Action to restore or enhance shellfish/mussel and mudflat/sandflat beds while also supporting plankton and zooplankton populations, which were of high importance to stakeholders in the coastal and offshore zones.
    • Consider intertidal invertebrates and offshore fish populations, which were also raised as important within future MNG compensatory actions.
  • Explore MNG preferences during decommissioning
    • Investigate the consultation-supported option of complete removal of offshore wind structures for decommissioning, where possible.
    • Encourage solutions that best fit site conditions and character, with abandonment of structures also considered positively as an option for biodiversity and environmental benefits.
  • MNG to incentivise strategic interventions  
    • Allow developers the flexibility to suggest either site-based or strategic interventions, depending on the site.
    • Highlight the feasibility of co-locating seaweed, mussel, and oyster farming, as well as Hydrogen/Carbon Capture Storage devices, with both fixed and floating wind farms.
    • Research and collaborative explorations around co-existence of fishing methods with, in particular, floating wind technology, should continue to be encouraged.
  • MNG within Marine Protected Areas (MPAs)
    • Further research into whether fixed and floating wind farms should be allowed to be built in UK MPAs is a priority.
Implementation of these recommendations should inform strategic considerations around natural resource management in the marine environment. For example, prioritising certain marine activities for co-existence, while also strengthening the consent process for offshore windfarm proposals. In doing so, better planned offshore windfarm projects have a better chance of, not just protecting, but restoring and enhancing seabed habitats, and acting as refuges for marine species.

Related information

Full paper: Stakeholder insights into embedding marine net gain for offshore wind farm planning and delivery
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