Offshore Wind Impacts
An estimated 12,000 offshore wind (OSW) turbines are in operation around the world. To date only minimal impacts have been reported, which can be mitigated. By contrast, OSW is one of the two main clean energy sources needed to prevent major ecosystem collapses, mass species extinctions, and food insecurity for billions of people. See Offshore Wind Benefits
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Comprehensive Research Portal for OSW Impacts
The most comprehensive OSW knowledge base for the U.S. offshore wind industry is the Synthesis of Environmental Effects Research (SEER), which synthesizes key issues and disseminates existing knowledge about environmental effects. Download the SEER Factsheet for a high-level summary. SEER is a multi-year collaborative effort that facilitates knowledge transfer for peer reviewed offshore wind research around the world to synthesize key issues and disseminate existing knowledge about environmental effects, inform applicability to U.S. waters, and prioritize future research needs. Through significant stakeholder outreach and engagement efforts, the research topics below were identified because they cover the range of stressor/receptor interactions, technology considerations, and cross-cutting themes that are pertinent to OSW development on both the U.S. Atlantic and Pacific Coasts.
The SEER research briefs on the seven categories of potential OSW impacts below and the scientific research papers that informed the briefs can be accessed here.
Underwater Noise Effects on Marine Life
MAIN TAKEAWAYS
- Underwater sound can be generated by biological, physical, and anthropogenic sources; unwanted sound sources, such as those from offshore development, are referred to as “noise.”
- During offshore wind (OSW) farm construction, the driving of foundation piles into the sediment generates a significant amount of noise for certain foundation types. As a result, a number of mitigation measures have been developed to reduce noise and minimize impacts to wildlife.
- Noise levels that can cause auditory injury are likely to occur in relatively close range to the pile driving. At greater distances, the intensity of noise is reduced (due to spreading) and is less injurious, but may still affect the behavior of marine species.
- Quieting technology, such as bubble curtains, are effective at reducing noise at the source, which has benefits for all marine species. Other mitigation measures, such as protected species observers or passive acoustic monitoring, can monitor areas for sensitive marine life to ensure that construction does not occur when they are in the vicinity through shutting down and delaying pile driving activities.
- The risk to marine life from underwater noise during other phases of wind farm development (e.g., site surveys, operations, and maintenance) is considered to be lower, but further monitoring is still needed to help fill existing research needs and gaps in understanding.
- For floating foundation types, mooring line anchors can be installed using a variety of relatively low-noise methods. When impact pile driving is used for the anchors, there is a smaller anticipated acoustic impact for these smaller piles.
Bat and Bird Interactions
MAIN TAKEAWAYS
- There is limited information on the risks to bats and birds from offshore wind turbines in North America, making it difficult for decision makers to site and operate wind farms that minimize potential collision risk and behavioral changes while maximizing wind energy production.
- Existing data from North America and Europe indicate that bats, particularly migratory tree-roosting species, approach and interact with land-based wind turbines, increasing their susceptibility to collisions. These interactions may also occur at offshore wind turbines. For some seabirds, such as terns and gulls, there is concern about potential collision risk. Other species, such as gannets and razorbills, may avoid or be displaced by wind farms.
- Monitoring bat and bird interactions at offshore wind turbines will require a combination of approaches, such as visual surveys, radar, cameras, strike indicators, tracking devices, and acoustic detectors, to determine species composition, assess behavioral changes, and detect collisions.
- Collision risk models may be an important tool for predicting collision risk for birds. The models are useful in comparisons across wind farms, wind turbine types, or species. They require specific data for different categories of birds (e.g., body size, flight height, and flight speed), avoidance behavior, and turbine characteristics, but the underlying assumptions are difficult to validate.
- Factors that may result in avoidance or attraction, such as lighting, wind turbine characteristics, turbine spacing, and proximity to high-use areas, should be considered when siting offshore wind farms.
- Minimization strategies that have successfully reduced bat and raptor collisions at land-based wind farms, such as curtailment and deterrents, need to be validated for offshore bat and bird species and modified to withstand the harsh marine environment.
Risk to Marine Life from Marine Debris & Floating Offshore Wind Cable Systems
MAIN TAKEAWAYS
•Primary entanglement risk: Current literature suggests that the risk of marine life becoming directly entangled with a floating offshore wind cable system (primary entanglement) is low; the mooring lines and cables have a large diameter and are sufficiently heavy which prevents them from looping and entangling marine life.
•Secondary entanglement risk: Marine debris, such as derelict fishing gear, may become snagged in floating offshore wind cable systems, which could potentially lead to the entanglement of marine life (secondary entanglement). There is insufficient information to evaluate secondary entanglement at this time.
•A broad range of marine life may be at risk of physically interacting with marine debris caught on floating OSW cable systems, including large migratory whale species (such as humpback and fin whales), fish species (such as whale sharks, basking sharks, and manta rays), sea turtles, seals, and diving seabirds, in part because of their feeding behaviors.
•Research is needed to develop more effective technologies for monitoring, detecting, and removing marine debris and derelict fishing gear snagged on floating offshore wind cable systems.
•Knowledge gaps related to marine life ecology are being addressed through ongoing research related to habitat preferences, migration patterns, and diving behaviors of marine life. This research will help inform future evaluations of entanglement risk.
Benthic Disturbance from Offshore Wind Foundations, Anchors, and Cables
MAIN TAKEAWAYS
•Foundations, anchors, and cables associated with offshore wind (OSW) energy development may alter the benthic environment during and after construction. Potential effects include alteration of habitat that displaces some invertebrate species, creation of new habitat that may increase invertebrate abundance and biodiversity, and physical and chemical changes to sediment structure.
•Most physical effects on benthic habitat are localized to the areas closest to OSW farm infrastructure and not spread throughout the entire wind farm area. Individual wind turbines occupy a small percentage of the total area of a wind farm, though the development of multiple wind farms would create more areas of change across a larger area.
•Benthic disturbance from displacement and suspension of seafloor sediment during construction tends to be temporary and recovery of the physical and biological conditions on the seafloor typically occurs within a few years.
•OSW foundations, anchors, exposed cables, and scour (or erosion) protection can alter the diversity and abundance of benthic organisms throughout the operational life of a wind farm. The components provide new hard substrate on the seafloor and in the water column that will favor some organisms over others, possibly leading to habitat conversion.
Effects on Fish Ecology from Offshore Wind Structures
MAIN TAKEAWAYS
•The placement of new structures during offshore wind (OSW) farm construction can temporarily or permanently alter the habitat directly beneath and in the vicinity of fixed-bottom turbine foundations, depending on the foundation type, materials used, and sediment type.
•Artificial reef effects have been documented at OSW farms based on the observed attraction of certain fish and invertebrate species to the turbine structures which provide a combination of hard vertical and horizontal substrates.
•Floating OSW farms are still a relatively nascent technology and less is known about their potential effects on fish and shellfish. Based on the technology type, they may have less of a direct effect on fish species and habitats because of the limited vertical profile of the floating foundation and smaller footprint associated with mooring and anchoring.
•Monitoring for changes in the biological community at OSW farms should be driven by specific objectives and hypotheses. Effective monitoring practices for understanding potential changes in fish communities at OSW farms include implementation of the BACI approach (before-after/ control-impact) or the BAG approach (before-after gradient) and data collection from trawl, trap and habitat surveys, fish tagging, and other methods.
•Examples of best management practices include siting projects away from sensitive habitats and minimizing seafloor disturbance during construction of the facility and associated infrastructure. Structures have the potential to be beneficial if they are specifically designed to meet the life requirements of a target population or a habitat need.
Presence of Vessels: Effects of Vessel Collision on Marine Life
MAIN TAKEAWAYS
- Marine life, including marine mammals and sea turtles, that spend significant time near the water surface or in areas where vessel routes overlap with migration, feeding, or breeding grounds have the potential to be struck by vessels associated with offshore wind energy development.
- There are two types of potential trauma associated with vessel collisions—blunt force and sharp force—both of which can result in death.
- The effects of vessel collisions are likely to be underrepresented due to a lack of reporting awareness and because not all struck marine animals are recoverable for documentation.
- Vessel speed reductions and route restrictions have shown to be effective mitigation measures for reducing the probability of injury and mortality related to vessel collisions.
- A broad evaluation of the risk of injury and mortality from vessel collisions on marine mammals and sea turtles associated with offshore wind activities is needed to develop effective mitigation measures that are species dependent.
Electromagnetic Field Effects on Marine Life
MAIN TAKEAWAYS
- Subsea power cables are sources of electromagnetic fields (EMF), which are made up of induced electric fields and magnetic fields.
- EMFs from natural sources also exist in the marine environment. Some marine animals, such as sharks, salmon, and sea turtles, can detect naturally occurring electric and/or magnetic fields and use those signals to support essential life functions, such as navigating and searching for prey.
- When in close proximity to subsea cables, some animals have demonstrated behavioral responses in a few studies, such as increased foraging and exploratory movements.
- So far, behavioral responses of individuals have not been determined to negatively affect a species population, but further research is needed to refine our understanding of the effects of EMFs on wildlife.