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As the world seeks to cut its reliance on fossil fuels, scientists have been working to harness the forces of nature—from the sun and the wind to the waves and the tides—to produce reliable sources of renewable power. But just like the energy sources they seek to replace, such as carbon-spewing oil and coal, these new sources of green energy will inevitably cause some environmental damage.
Skeptics and scientists have raised a range of hypothetical ways in which wave and tidal power infrastructure could hurt animals. Maybe seals, seabirds, and fish will be sliced and diced by underwater turbines. Perhaps they will be disturbed by the sounds of underwater generators. Sharks and rays—sensitive to electromagnetic fields—might be thrown astray by subsea power cables. Seawater and sediment could be churned up, disrupting migrating and feeding animals. As with any new technology, it’s difficult to accurately gauge the actual threat posed by any of these imagined scenarios.
That’s why Andrea Copping, an offshore energy expert at the US Department of Energy-funded Pacific Northwest National Laboratory, set out to assess the risks posed by common forms of ocean energy infrastructure. She finds that tidal turbine blades present the most immediate danger to wildlife, but impacts would be rare, and in most cases non-lethal.
Through laboratory experiments and modeling scenarios, Copping and her team analyzed which of the proposed threats might pose a danger to ocean ecosystems. Crucially, they also sought to put these dangers in context, comparing them against the better-known dangers posed by offshore wind farms, oil platforms, and ships. The team presented their preliminary findings at a scientific conference in Portland, Oregon, earlier this month.
In one experiment, Copping and her team used blubber and skin from dead killer whales and harbor seals to simulate the effects of the animals being hit by turbine blades. They also modeled the odds that a harbor seal would interact with such devices in a way that it would get hurt.
Ultimately, they found that the threat of most planned wave and tidal energy setups is quite low—especially when compared to other coastal energy projects, such as offshore oil drilling.
An animal hit by turbine blades might be bruised, Copping says, but the damage is unlikely to be fatal. The wave energy industry has not settled on a favored design, but most prototypes involve fewer moving parts than tidal turbines. All marine energy systems have power cables that could potentially affect sharks’ and rays’ sense of electromagnetic perception, Copping says, but only in the cables’ immediate vicinity.
The findings echo previous research says Beth Scott, a zoologist at the University of Aberdeen in Scotland. Her colleagues have used dead seals to test the damage turbines can cause, and except for at the blades’ tips, they usually move too slowly to be lethal to marine mammals, though injuring even a single endangered animal, such as a killer whale, would be a major problem.
People tracking tagged seals near an experimental wave energy project off Scotland have not reported any injured or killed animals, Scott adds.
But there is still the potential for chronic and cumulative damage caused by noisy machinery and churning water, says Sarah Henkel, an ecologist at Oregon State University. Slightly but repeatedly modifying the flow of water could disrupt the migration and foraging of some fish species, she says, while the circulation of sediment could affect seafloor animals.
Ocean power infrastructure will also require construction and maintenance, and will likely drive increased boat traffic, Henkel adds, which could disrupt marine wildlife more than the devices themselves.
But Copping notes that wave and tidal energy systems work best in high energy seas, with water that is rough and hard to work in. “No one spends longer at sea with vessels in these harsh parts of the ocean than can be helped,” she says.
The industry has been moving slowly, making it difficult to predict how problematic such long-term issues might be. Henkel says she and other researchers are monitoring ongoing trials, and watching for any potential environmental effects.
In any case, Copping thinks wave and tidal energy have an important role to play. “I think we need to take a varied energy portfolio approach, and I think marine energy has a real place in that,” she says.
“We’re trying to learn more, and we’re trying to convince regulators and stakeholders that it’s probably not the risk they imagine.”