Journal of Environmental Management 307 (2022) 114577 Available online 25 January 2022 0301-4797/© 2022 Published by Elsevier Ltd. Potential impacts of floating wind turbine technology for marine species and habitats Sara M. Maxwell a, * , Francine Kershaw b , Cameron C. Locke a , Melinda G. Conners c , Cyndi Dawson d , Sandy Aylesworth e , Rebecca Loomis b , Andrew F. Johnson f, g a School of Interdisciplinary Arts and Sciences, University of Washington, Bothell, Bothell, WA, USA b Natural Resources Defense Council, 40 West 20th Street, New York, NY, USA c School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY, USA d Castalia Environmental, Hanover St, Santa Cruz, CA, USA e Natural Resources Defense Council, 111 Sutter St, San Francisco, CA, USA f MarFishEco Fisheries Consultants, 67/6 Brunswick Street, Edinburgh, EH7 5HT, Scotland, UK g Marine Sustainability, Policy & Conservation Evidence (Marine SPACE) Group, The Lyell Centre, Institute of Life and Earth Sciences, School of Energy, Geoscience, Infrastructure and Society, Heriot-Watt University, Edinburgh, EH14 4AS, Scotland, UK A R T I C L E INFO Keywords: Renewable energy Floating offshore wind technology Secondary entanglement Habitat displacement Turbine collision Turbine configuration ABSTRACT Offshore wind energy is expanding globally and new floating wind turbine technology now allows wind energy developments in areas previously too deep for fixed-platform turbines. Floating offshore wind has the potential to greatly expand our renewable energy portfolio, but with rapid expansion planned globally, concerns exist regarding impacts to marine species and habitats. Floating turbines currently exist in three countries but large- scale and rapid expansion is planned in over a dozen. This technology comes with unique potential ecological impacts. Here, we outline the various floating wind turbine configurations, and consider the potential impacts on marine mammals, seabirds, fishes and benthic ecosystems. We focus on the unique risks floating turbines may pose with respect to: primary and secondary entanglement of marine life in debris ensnared on mooring lines used to stabilize floating turbines or dynamic inter-array cables; behavioral modification and displacement, such as seabird attraction to perching opportunities; turbine and vessel collision; and benthic habitat degradation from turbine infrastructure, for example from scour from anchors and inter-array cables. We highlight mitigation techniques that can be applied by managers or mandated through policy, such as entanglement deterrents or the use of cable and mooring line monitoring technologies to monitor for and reduce entanglement potential, or smart siting to reduce impacts to critical habitats. We recommend turbine configurations that are likely to have the lower ecological impacts, particularly taut or semi-taut mooring configurations, and we recommend studies and technologies still needed that will allow for floating turbines to be applied with limited ecological impacts, for example entanglement monitoring and deterrent technologies. Our review underscores additional research and mitigation techniques are required for floating technology, beyond those needed for pile-driven offshore or inshore turbines, and that understanding and mitigating the unique impacts from this technology is critical to sustainability of marine ecosystems. 1. Introduction There is scientific consensus that decarbonization of the world’s energy system is imperative, if humans are to avoid catastrophic climate change (IPCC, 2014). With projected, and in some cases already observed, changes in marine ecosystems due to ocean warming from climate change (Bryndum-Buchholz et al., 2019; Descamps et al., 2017; Henson et al., 2017; Rogers et al., 2020), there is global support for sustainable energy development, and the marine environment holds significant promise for renewables, particularly offshore wind energy. Wind energy is slowly becoming a more cost-competitive and cost-effective renewable energy resource (Bogmans, 2019). Offshore wind energy deployment has increased around the world, because winds at sea are much stronger and much more consistent than terrestrial * Corresponding author. E-mail address: smmax@uw.edu (S.M. Maxwell). Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman https://doi.org/10.1016/j.jenvman.2022.114577 Received 2 June 2021; Received in revised form 13 January 2022; Accepted 19 January 2022