Ocean Wind Farms and Their Effects on Ocean Life

The easiest way to avoid any negative impacts from wind farms is to site and place turbines properly. Obviously, wind farms should avoid sensitive marine habitats and vulnerable species which occur closer to the shoreline. Interestingly, when people in Denmark were surveyed about siting wind farms farther from shore to maintain scenic views, they responded that they would pay more for this option. Denmark currently has the largest offshore wind farms and generates about 15% of its electricity from wind power.

Less obvious is the idea that turbines should be spaced far enough apart to avoid the cumulative noise impacts of the interior gear boxes where kinetic wind energy is converted into electricity. Adequate spacing also allows fishing vessels to sail freely within turbine arrays while huge blades are spinning. It turns out, once wind farms are constructed, they increase fishery abundance by providing good habitats helping a fishing industry that has been hurt by declines in recent years.

Negative impacts associated with offshore wind farms generally occur during the construction phase. Construction activities require transporting equipment offshore, trenching, dredging, driving pilings and setting concrete into the sea bed, all of which tear up benthic habitats. Fish and marine mammals can be disturbed during the construction phase when higher than normal noise frequencies occur as pilings are driven into the sea bed. However, abnormal fish and marine mammal responses have not been observed when frequency decibels are kept below a certain level. During normal operation, turbine movement does create some noise, but the frequency is too low to cause negative responses in fish or marine mammals.

Once wind turbines are sited and constructed properly, the positive impacts begin to appear. Below the ocean's surface, the supporting pilings become new marine habitats supporting strong benthic communities that result in bigger mollusks and crustaceans, increased diversity, structural complexity and food sources for fish and birds higher up on the marine food chain. These artificial reefs provide additional food, shelter and spawning areas enticing fish to gather within the turbine array.

The benefits are even more pronounced when you consider how offshore wind farms supplant fossil fuel use. They decrease carbon dioxide (CO2) emissions lessening the burden on the ocean. Apparently, the oceans are very good at absorbing atmospheric CO2, an important process to alleviating climate change, but a process which also creates acidic water that destroys coral reefs. Offshore wind turbines create artificial reefs that offset losses in other areas.

In the US, alternative energy projects are receiving a lot of support and some criticism. The government provides financial support through tax credits and grants, but also regulates wind energy projects similarly to a coal plant, increasing costs. Environmental Impact Statements (EIS) are required as well as compliance with the Department of Interior's Minerals Management Service's permitting process and National Marine Fisheries guidelines. Compliance with all of these programs mitigates any negative impacts.

Mitigation processes include; siting to avoid habitats like seagrass beds, anchors to reduce electric transmission cable sweep which can damage habitats, noise monitoring during the construction phase to confirm low frequencies when driving pilings, anti-perching devises to keep birds away and approval of Operation and Maintenance (O&M) plans that describe schedules and activities to keep wind farms functioning properly.

The good news is that wind farms offset CO2 impacts by decreasing dependence on fossil fuels. Better news is that wind farms sited properly, farther offshore, create artificial reefs that benefit ocean life and help the fishing industry. Wind farms create positive effects on ocean life and are a win-win situation for humans and the earth.

Department of Interior Minerals Management Service, Cape Wind Final Environmental Impact Statement

Madsen, et. al., Wind turbine underwater noise and marine mammals: implications of current knowledge and data needs.

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