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Environmental Impact Assessments for Offshore Wind Farms

offshore wind farm
Environmental impact assessments are crucial in determining how offshore wind farms will impact our world.
(cc) Kim Hansen

Wind power has proven itself to be a viable component of renewable energy portfolios. Installations, ranging from single small residential turbines that produce a few kilowatts, to wind farms consisting of dozens of megawatt turbines covering hundreds of acres, are sprouting up around the world. Unfortunately, wind power is not without its drawbacks. Utility-scale turbines inevitably have an impact on their environment. This is obvious with onshore turbines, where nearby residents may view them as noisy eyesores that reduce property values, but the effects are less apparent with offshore turbines, where they are out of sight and out of mind.

Measuring and mitigating the effects of offshore wind farms requires comprehensive environmental impact assessments. How are such assessments carried out and what should they cover?

Timing Is Everything

Environmental impact assessments begin long before the turbines start spinning. In order to gauge how a wind farm may affect the local environment, we need a clear picture of the environment first. Painting such a picture takes time. It’s not enough to take a one-time count of local bird and fish species. Populations vary over the course of a year as animals migrate, as they reproduce, and as their food supply changes.

Even a full year is not enough to establish a solid baseline for an environmental impact assessment. Weather patterns are rarely identical year to year, and may cause variations in animal behavior and populations. After the construction of a wind farm, the population of a specific species of sea bird may be lower than that observed the year before construction. But was that observation typical? Was the previous year unusually high? Or unusually low? We need data collected over several years before we can arrive at an accurate answer.

Where possible, environmental assessments should be carried out for at least three years before wind farm construction begins, continue during construction, and then for another three to five years after the wind farm becomes operational.

More Than Just Counting

Conducting an accurate environmental impact assessment involves more than just counting birds or fish. It requires knowing as precisely as possible where those birds and fish are at any given time, where they’re going, and what they’re doing. It means understanding how those birds and fish interact with each other and with other species.

How is this data gathered? Much of it comes from direct observation, watching birds from the shore, or fish from beneath the water. Surveys may also employ weather and military radar — although these are often configured to ignore flocks of birds — as well as thermal imaging.

Birds may be attracted to the superstructure of turbines as nesting sites or rest stops on their migration. Otherwise, migrating birds usually give turbines a wide berth, at least in daylight hours. If they don’t, the altitude at which they fly, above or below rotating turbines, is obviously significant. Night-flying birds are known to collide with stationary objects in their trajectory, both at land and at sea, and of course spinning turbines pose an additional hazard. It may seem that a simple solution would be to add illumination. However, lights may actually attract birds, or insects on which birds feed.

Fish species may benefit from offshore wind farms … or not. The moorings of floating turbines provide a foundation for corals and may attract fish species previously absent from the area, or increase the population of indigenous species. But this may in turn attract birds who feed on these fish.

Environmental assessments of offshore wind turbines also need to consider onshore factors, such as power transmission lines, as well as other offshore turbines. This is because there may be cumulative effects between sites. As birds increase the length of their migration to avoid obstacles, their energy requirements go up. If they then need to avoid additional obstacles, their energy requirements may exceed their reserves. If that happens, their mortality rate will likely increase.

The Butterfly Effect

Given the time and expense necessary to conduct a thorough environmental impact assessment, we could ask, is it really worth it? Is it such a problem if a few birds have to fly around a wind farm, or if they fail to fly around it and get caught in the turbines?

All living things are interconnected. Individual birds contribute to flocks; flocks contribute to species; species contribute to a balanced ecosystem. Even if the species directly influenced by offshore wind farms are not seriously affected, they may disrupt other species, including those that are already endangered. This can lead to severe consequences for humans as well. Consider …

A flock of migrating birds has to fly farther to avoid a wind farm. Some of the birds don’t make it. With their reduced numbers, there are fewer birds to feed on a certain species of insect. These insects reproduce uncontrolled and displace other insects which would otherwise pollinate food crops. Fewer pollinators lead to reduced harvests, leading to food shortages.

Although environmental impact assessments are costly and time-consuming, they are essential for our own advantage and that of our environment. This is why many countries pursuing renewable energy projects, including both onshore and offshore wind turbines, have established laws requiring such studies. The more in-depth assessments we conduct, the greater our understanding of our environment, and the more success we’ll have in working with our world, instead of against it.

Read Wind Energy Systems: Control Engineering Design from Amazon.

Jules Smith is the principal of LightningStrike Studios, a professional writing firm specializing in renewable energy and information technology.

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