A sea change

31st May 2024

Joe Nisbet explores the challenges and opportunities of delivering marine net gain through offshore renewables

The interlinked crises of biodiversity loss and climate change are being felt globally. The UK State of Nature report, for example, found that the abundance of species studied in the UK has declined by 19% on average since records began. Behind 2022, 2023 was also the second warmest year on record for the UK.

Offshore renewables, particularly offshore wind farms (OWFs), are a major piece of the decarbonisation puzzle; a piece in which the UK is keen to position itself as a market leader with an ambition to deploy up to 50 gigawatts of offshore wind capacity by 2030.

Offshore wind is not only an opportunity to minimise and offset impacts on the marine environment, it can also be used to regenerate and enhance it. OWFs are increasingly being designed with marine net gain (MNG) in mind, with ‘nature-inclusive designs’ of components such as scour protection (the stones placed around the base of turbines) and cables to create new habitats for benthic and reef ecosystems. Restoration of oyster/mussel beds and novel technologies such as ‘fish hotels’ are also being tested around European sites and are snapshots of the exponential growth of MNG.

Doubling up

Enhancement activities also extend beyond species-specific benefits to wider ecosystem services. There are initiatives to unite the aquaculture and OWF sectors – for example, a pilot project to develop the world’s first commercial-scale seaweed farm within an OWF.

Marine enhancement is less mature than its terrestrial counterpart, however. While biodiversity net gain (BNG) is now a UK legal requirement for all town and country and national infrastructure planning development, no such mandate exists offshore. What constitutes successful marine enhancement is still evolving, not only in terms of nature recovery but also for the people who depend on our oceans for their livelihoods.

There are still unknowns around the definition and application of net gain within marine contexts and how this can be mandated. While clearer regulation of MNG is expected to come, different approaches are likely to be taken across the UK’s devolved nations and currently none of the national marine plans include explicit MNG policies.

Reliable marine biodiversity data is also often limited, with the risk that marine species are under-represented in assessments. This is compounded by the fact that marine habitats as a sole indicator also offer weaker proxies for species compared with terrestrial environments, owing to greater species mobility. Uncertainty in assessing marine biodiversity also highlights the risk from external pressures such as invasive species, which could use nature-inclusive designs/OWF structures as artificial reefs on which to proliferate. The novelty of such designs may also mean higher costs and uncertain maintenance requirements, which could be prohibitive to developers in the absence of mandated MNG.

Barriers also exist to facilitating collaboration between stakeholders with differing views in what is an increasingly busy space (in particular, fishing and environmental sectors); for example, removing external human pressures, such as fishing, from OWF sites may provide environmental benefits but to the discontent of the fisheries sector.

The scale of investment in offshore renewable energy, however, presents a unique opportunity to study impacts, look at successes and failures, gather crucial baseline habitat and species data, and canvas stakeholder views. There are forthcoming commitments to deliver a coherent approach to MNG. This may involve developing a new MNG metric that is fit for purpose and reflects the nuance of assessing marine biodiversity. An industry levy to feed into a strategic nature enhancement fund is also being considered.

Making the best use of space

There is also the opportunity for marine enhancement to expand on BNG and be more holistic, incorporating the social, environmental and economic benefits of natural assets. Specific ecosystem services that could be provided include helping maintain productive fish stocks and nursery habitats. The open, connected nature of marine environments also means OWF developers could make strategic interventions beyond site-level measures. As competition for seabed space continues, this may enable other marine activities to co-exist in OWF areas such as seaweed/mussel farming and carbon capture/hydrogen storage facilities.

Optimised and efficient use of space that delivers clean energy, productive and sustainable food systems and positive benefits for nature is paramount. With robust policy and clear regulatory requirements, careful marine spatial planning and proactive cross-sector working, offshore renewables can be leveraged to secure both nature enhancement and net-zero objectives.

Joe Nisbet is an environmental consultant at Arup and a member of the IEMA Futures Steering Committee


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