The North Sea is one of the most industrialised marine environments on the planet, with thousands of man-made structures (MMS) including oil and gas platforms, pipelines, subsea cable routes, and marine renewable energy installations. Much of the infrastructure relating to the oil and gas industry has been in place for decades and is coming to the end of its economic life. In contrast, the marine renewable energy industry is expanding with many windfarms planned for construction in the near future. Current legislation requires that MMS in the North Sea should be removed from the marine environment after their operational lifespan is complete. With the decline of the oil and gas sector, the UK decommissioning operation will cost around £50 billion, with almost half of the financial burden falling on the taxpayer. These forthcoming changes in the North Sea landscape may have a significant impact on marine life. There is mounting evidence that the effects of MMS on the local marine environment are complex, and depend on the age, type, and operational status of the MMS. Once installed, MMS can host artificial reefs supporting diverse communities of marine life. Further, the exclusion of shipping and fishing in the vicinity of many MMS may provide refuges for fish and predators such as sharks, seals or porpoises (de facto Marine Protected Areas). However, the true extent of the effects of MMS on the ecosystem are unclear. To ensure effective decision-making about removal and installation of such structures in the future, there is an urgent need to better understand the impact of MMS on the North Sea ecosystem.
EcoSTAR (Ecosystem-level importance of STructures as Artificial Reefs) is a collaborative project combining the expertise of marine ecologists from the Sea Mammal Research Unit (SMRU) at the University of St Andrews and the Centre for Environment, Fisheries and Aquaculture Science (Cefas). EcoSTAR aims to fill in the key knowledge gaps on the impact of MMS across the entire marine ecosystem. This ecosystem-wide approach is critical to fully understand the breadth of possible interactions between MMS and marine species. To achieve this, EcoSTAR will measure impacts of MMS from the bottom of the food chain (the benthic community) all the way to the top (marine mammals). EcoSTAR will 1) improve our understanding of the importance of MMS as habitat for benthic communities such as mussels, anemones and starfish; 2) measure how MMS influence the distribution and movement patterns of marine mammals in the North Sea; 3) determine how many seals and porpoises forage at MMS, and how often, and estimate the associated benefits or costs of MMS to individual animals; and 4) estimate the consumption of fish by seals and porpoises feeding around MMS. Critically, the knowledge gained from this project will be combined with existing data and knowledge of fish, food webs and fisheries, to predict the impacts of MMS on the whole ecosystem using cutting-edge ecosystem models. This will allow the prediction of the impacts of removing old structures (such as oil and gas platforms) and installing new structures (including wind turbines) on the marine ecosystem and on commercial fisheries The findings of EcoSTAR will facilitate the development of environmentally sustainable management strategies for the North Sea as whole, and specifically with regard the addition and removal of MMS.

Potential Impact:
EcoSTAR will provide a knowledge base on which policymakers and regulators can make informed decisions on the removal and addition of man-made structures (MMS). More generally the findings will enhance our understanding of the North Sea ecosystem, facilitating its sustainable management. EcoSTAR has a wide range of beneficiaries including regulators, policymakers, industry, and the general public.
The project outputs will be critical to the 2023 review of OSPAR Decision 98/3. Currently, this legislation requires the removal of most obsolete structures from the North Sea which comes at significant cost. The current estimate for UK decommissioning is c.£50 billion with around half to be paid by the taxpayer.
The outputs will also be important to the Marine Renewable Energy (MRE) industry. At present, uncertainty over the effects of new MMS installations on marine biota is a constraint on UK MRE developments, frustrating efforts to meet carbon reduction targets. The energy industry represents 4.5% of GDP in the UK economy. If viable growth can be achieved, the MRE sector could maintain the vibrancy of the UK energy industry, providing direct economic benefits and enhanced energy supply security. The outputs of EcoSTAR will inform the site-specific mitigation requirements of MMS installation and removal.
More generally, the spatial distribution of benthic invertebrates, fish and marine mammals across the North Sea, and information on the drivers of distribution and foraging, will inform marine spatial management to meet internationally agreed biodiversity objectives including the UN Convention on Biological Diversity and Sustainable Development Goals, and the Marine Strategy Framework Directive that is enshrined in the UK Marine Strategy. Outputs will provide timely support for the Government's 25 Year Environment Plan, and contribute to the Good Environmental Assessments for the UK Marine Strategy and OSPAR biodiversity assessments. EcoSTAR will also facilitate the effective placement of future designated and de facto MPAs, and demonstrate their impact on the ecosystem.
By furthering our understanding of the interactions between predators and commercial fish species, the findings will support fisheries management in addressing the ecological impacts of fisheries; this is essential to implement both the "sustainability objective" and "ecosystem objective" of the UK Fisheries Bill. The results will improve estimates of marine mammal predation in stock assessment models. Further, EcoSTAR will assist in the drive towards an ecosystem approach to fisheries management, enabling advice and quotas based on stock assessments to be expanded to explicitly include impacts of fisheries on the prey availability to top predators
The outputs will directly benefit statutory regulators and advisors including the Department for Environment, Food & Rural Affairs (Defra), Marine Management Organisation (MMO), International Council for the Exploration of the Sea (ICES), OSPAR- ICG groups, and Marine Scotland (MS), to refine advice and target conservation actions. To highlight the importance of the work, the International Council for the Exploration of the Sea (ICES), Natural England (NE), Scottish Natural Heritage (SNH), the Joint Nature Conservancy Council (JNCC), and the Department for Business, Energy and Industrial Strategy (BEIS) have provided letters of support and in-kind contributions to the project. Their involvement will facilitate the timely dissemination of data and results throughout the project. Moreover, this work will be important to industry and the general public given the financial implications of structure decommissioning, and the increasing public awareness of the importance of the marine ecosystem for critical services, such as climate regulation and food production.