The OES-Environmental 2020 State of the Science Report: Environmental Effects of Marine Renewable Energy Development Around the World builds on and serves as an update and a complement to the 2013 Final Report for Phase 1 of OES-Environmental and the 2016 State of the Science Report. Its content reflects the most current and pertinent published information about interactions of marine renewable energy (MRE) devices and associated infrastructure with the animals and habitats that make up the marine environment. It has been developed and reviewed by over 60 international experts and scientists from around the world as part of an ongoing effort supported by the OES collaboration that operates within the International Technology Cooperation Framework of the International Energy Agency (IEA).
The 2020 State of the Science Report consists of 14 chapters which can be downloaded as a whole or individually. Download Chapter 3: Collision Risk for Animals around Turbines here.
Tidal and river energy devices may pose a risk of collision to marine mammals, fish, and seabirds. Factors that influence the likelihood of collision include the characteristics of the device, animal behavior, and the number of animals in the vicinity of the moving parts of devices. To date, there have been no observations of a marine mammal or seabird colliding with a turbine, and the limited number of interactions observed of fish in close proximity to a turbine have not resulted in obvious harm to the fish. It is expected that collisions, if they occur, will be very rare events, so that observing them in the fast-moving, often murky water will be very difficult. In addition, the likely consequences of a collision are not known, and could result in injuries from which the animal may recover, or may result in the death of the animal. There is limited evidence and understanding of how marine animals behave in the presence of underwater structures; it is difficult to determine how well marine mammals, fish, and seabirds may be able to sense, react to, and avoid an operating turbine. In the absence of this behavioral information, most progress in understanding collision risk focuses on understanding the presence of marine animals of interest in the vicinity of turbines, supported by computer modeling that simulates potential collisions.
Monitoring around deployed turbines, using underwater video and active acoustics such as echosounders and acoustic cameras, has provided increased understanding of the presence and some limited insight into the behavior of marine mammals. This is particularly true for the behavior of seals and porpoises relative to several types of bottom-mounted and floating turbines, as well as a tethered tidal kite. These data are being applied to collision risk and encounter risk models in supporting consenting applications. The consequences of marine mammals colliding with turbines has been explored using techniques including ramming dead animals with a simulated turbine and testing marine mammal tissue for damage using forces likely to be produced by turbines, resulting in the likely potential for a range of damages to occur. More information is needed to fully evaluate this risk to marine mammals, particularly as new designs and deployment locations are explored for MRE development.
To better understand the collision risk to fish, numerical models are being used to estimate the probability of fish encountering a turbine, the consequences of a fish colliding with a turbine blade, and ecological risks to the population if collisions occur. Laboratory studies have used a small turbine in a flume or tank to understand how fish may interact with the turbine, and some limited field studies around deployed turbines have been conducted. These studies have shown that many fish appear to actively avoid the turbine, while others swim unharmed through the turbine.
Concerns about seabirds colliding with operating turbines as they dive for food have focused on the presence of seabirds species in the areas where tidal turbines are planned, the specific manner in which the birds use these habitats, and some of the oceanographic processes that might make encounters with turbines likely.
The Short Science Summary for the chapter is available here.