Disturbance impacts of planned offshore wind expansion on UK sediment blue carbon stocks

Abstract

The growth of offshore wind to meet the UK’s green energy targets will have impacts on marine ecosystems and other marine users. The large-scale construction of offshore wind infrastructure to meet these requirements could affect the blue carbon stocks stored in the UK’s seafloor sediments. Two pathways of disturbance from offshore wind expansion were identified in the present study: from the displacement of bottom-towed gear fishing and from infrastructure construction. These pressures were spatially modelled to determine if future offshore windfarm expansion in UK waters poses a threat to sediment blue carbon stocks. Results showed that only 2.02 % of the UK’s sediment blue carbon stock would be de-facto protected by planned offshore wind areas. Fisheries displacement from planned offshore windfarm areas to proximate seabed areas increased blue carbon disturbance in the UK waters by 0.35 % from the baseline disturbance scenario. Secondly, disturbance from planned offshore windfarm infrastructure construction was found to range from 29,600 to 141,000 tonnes for minimum and maximum scenarios respectively. Inter-array cable laying was responsible for ∼90 % of sediment blue carbon disturbance when compared to construction of scour protection and foundations. In conclusion, blue carbon disturbance in the top 10 cm of sediment from fisheries displacement and infrastructure construction are relatively small. But, due to the possibility of future fisheries displacement from continued spatial expansion of offshore wind, the present study supports the introduction of marine spatial planning measures that would reduce disturbance and protect sediment blue carbon.