This article was originally featured on Hakai Magazine, an online publication about science and society in coastal ecosystems. Read more stories like this at hakaimagazine.com.
Addressing the climate crisis—hitting net-zero global carbon emissions by 2050—calls for big solutions. Fossil fuel emissions need to drop, and alternative energy sources need to ramp up. And in pursuit of that goal, one literally big solution—offshore wind energy, with its many massive turbines—is set to get much, much bigger.
Right now, the world’s offshore wind turbines—mainly in the United States, the United Kingdom, Europe, and China—are putting out a collective 75 gigawatts of power each year. That’s about half as much power as Canada produces annually from hydro, nuclear, fossil fuels, wind, solar, and other renewables. To hit the world’s climate goals, projections suggest the world’s offshore wind capacity needs to scale to 2,000 gigawatts by mid-century. That would mean installing a whopping 5,000 new turbines in the ocean every year for the next 25 years.
But building, operating, and, eventually, decommissioning such a monumental new energy system—even a renewable one—will affect the ocean in unavoidable ways.
Building an offshore wind farm is a vast technical undertaking. Construction crews—housed in floating hotels—use giant equipment to piledrive anchors into the seabed. Others lay heavy-duty submarine cables and build offshore electrical substations. Once the turbines are running, maintenance crews sail out to keep the blades humming along with the ocean’s forceful winds. All of this creates opportunities for ship strikes, collisions with the turbines, and an onslaught of underwater noise.
There’s real potential for environmental harm, but the discussion around offshore wind has been plagued by rampant misinformation—propagated in part by Donald Trump, the former US president and current Republican presidential candidate. Trump has threatened to use his executive powers to disrupt the expansion of offshore wind if he wins a second term in November 2024. Meanwhile, oil and gas interests—responsible for worsening the climate crisis and harming birds and whales with spilled oil—are funding misinformation campaigns opposing offshore wind projects along the East Coast of the United States.
Also along the East Coast, more whales have been dying since 2016. A 2024 study tied the spike in deaths to the fact that young humpback whales are expanding into new feeding grounds, leading to increased interactions with fishing gear, and ship strikes. Yet the people spreading misinformation have tried to hook the whale deaths to the construction and operation of a few recent offshore wind farms. “The science is definitely showing that’s not the case,” says Patrick Halpin, a marine geospatial ecologist at Duke University in North Carolina. Still, some small community groups, sometimes with support from free-market think tanks and fossil fuel interests, have relied on cherry-picking data and promoting fake experts to wrongly pin the blame on offshore wind—despite the timing and locations of whale deaths aligning with increased ship traffic and fishing gear entanglements.
But in a pair of recent comprehensive reviews, Anaëlle Lemasson, a marine ecologist at the University of Plymouth in England, and her colleagues have cataloged all the real environmental consequences offshore wind turbines are expected to have. Their literature review and meta-analysis reveal the current state of scientific understanding of the ecological trade-offs that will accompany the switch to offshore wind. From there, they point to places where society can help avoid the worst of these unintended consequences.
In the first study, the researchers pored through 132 existing peer-reviewed studies to examine how offshore wind turbine construction and operation affect key ecosystem services, such as the availability of food and the quality of the water. In the second study, the scientists attempted to look into the far future—to figure out the environmental effects of a decommissioned wind turbine.
Construction
Most research on offshore wind energy’s potential environmental impacts, Lemasson and her colleagues found, stems from studies of turbine construction and operation in the United Kingdom, the European Union, and the United States.
Predictably, construction causes a lot of problems, including destroying habitat, raising the risk of collisions, disrupting animals with noise and electromagnetic fields, introducing invasive species, and having so-called “visual and aesthetic” effects. Turbine construction harms several fish species (cod, for example) and some bird species, such as the common guillemot.
And, as more turbines are deployed, researchers expect this damage to scale up.
Operation
Once built, a turbine has mixed effects. Lemasson and her colleagues found that functioning wind turbines have both positive and negative environmental consequences that are roughly equal in measure.
“It’s a balance between harms and benefits,” says Lemasson. “There have been cases where birds of conservation importance have used the platform as nesting grounds, for example.”
Many studies that focused on the impact of wind turbines during their operational lifetimes looked at their effects on fish, birds, and marine mammals. Notably, research shows that operating offshore wind farms has no observable effects on whales and other marine mammals. Scientists can’t say, however, whether offshore wind is positive, negative, or neutral for other species, such as sea turtles and sharks.
Of all the environmental consequences—both positive and negative—cataloged in the review study, Lemasson and her team found that, overall, offshore wind farms have slightly more negative effects than beneficial ones, with lots of studies showing how situational the consequences can be. The authors write that different species are often affected in various ways, so whether a turbine’s effects are good or bad really depends on what you care about. (It’s worth clarifying that the analysis only includes the direct effects the turbines have on the environment, so it deliberately overlooks the climate benefits of switching to a renewable energy source.)
Afterlife
What happens after a wind turbine reaches the end of its roughly 25-year lifespan remains a black box.
Because the young industry’s first turbines only went into the ocean in 1991, scant few have been decommissioned. Lemasson and her colleagues found no peer-reviewed studies that assess how removing or dismantling a wind turbine affects the surrounding ecosystem.
Within the offshore wind industry, developers and regulators have yet to chart a clear path for what decommissioning an offshore wind turbine would even look like. Will they remove the whole structure? Or only part of it? Will they leave it in the water as an artificial reef? “It is concerning, isn’t it?” says Lemasson.
Lacking direct studies on decommissioning, Lemasson and her colleagues worked in reverse. While they can’t say how removing a wind turbine would affect the ecosystem, they’re certain that decommissioning one would undo the benefits turbines can yield. So, they examined how operational turbines affect, say, fish abundance or invertebrate biodiversity, then concluded that removing the structures would undo that effect.
“The overall answer is the benefit is very limited,” says Lemasson. Like many artificial structures in the ocean, an offshore turbine can lure fish in from elsewhere. “This doesn’t actually mean that it’s producing fish,” she says, just that more fish are in the area.
In the United Kingdom, a recent policy push would require offshore wind projects to contribute to a net increase in biodiversity. Lemasson and her teammates explored whether leaving decommissioned turbines in the water to serve as potential artificial reefs could help hit such a goal. “In very familiar and lay terms,” she says, a decommissioned wind turbine “is just not doing much”—neither positively nor negatively.
While scientists are attuned to the lessons offered by the offshore wind industry’s short history, much more data is needed—especially when it comes to questions that are specific to certain regions, species, or time frames, says marine ecologist Shayna Sura, who is part of a working group preparing for the possibility of offshore wind in the Gulf of Mexico. “How do those impacts look after five years, 10 years, 20 years?” Sura says.
Offering people real, meaningful discussions about offshore wind’s potential impacts is critical, adds Sura. “It’s important to think about this in terms of this shift from one type of habitat to another” she says. “You are going to lose some things in order to gain some things.”
Halpin, the ecologist from Duke University, emphasizes that precise science and deliberate timing is key to avoiding unnecessary conflicts between offshore wind power and wildlife. “When you build the site, when you do the maintenance, when you do that decommissioning is as important as where you put it,” he adds.
Ultimately, says Halpin, given that the switch to renewable energy includes a drawdown of fossil fuel emissions and a reduction of planet-heating greenhouse gases, the issues at play amount to “second-generation environmental conflicts—where we have one environmental good versus another environmental good.”
Still, he underscores that these challenges aren’t insurmountable. “This can be done,” he says. “It’s something that can be managed in a thoughtful way.”
This article first appeared in Hakai Magazine and is republished here with permission.