Do electric cables from offshore wind energy sites endanger marine species?
At a Glance:
You may have heard about the cables that carry electricity generated by offshore wind turbines to land based stations. The cables used in offshore wind are not much different from those used to carry power on land. Although they are buried on the seafloor, they do emit electric and magnetic fields (EMF) just as they do on land. While the burial reduces the emissions, it does not eliminate them. Thus, it is reasonable to ask whether these transmission lines affect marine species that encounter them.
You may be surprised to learn that the burying of high-voltage electric cables on the seafloor is not new or unique to offshore wind. There are already five undersea transmission lines connecting Long Island and the Continental United States as of 2021 (Source: Wikipedia). They are also used widely all over the world, including the 450 mile North Sea Link, which connects Norway with the United Kingdom.
The cables beneath Long Island Sound were used in experimental studies by University of Rhode Island scientists to determine what we know about behavior of local lobster and skate species in response to encountering EMF like that which will be emitted by offshore wind farms. Not surprisingly, because marine species use the natural EMF of the earth to navigate and even sense nearby predators and prey, changes in swimming and foraging behavior of individuals were detectable.
The Earth’s natural magnetic field varies from point to point on the surface. In Rhode Island it is about 50 micro Tesla. The magnetic field emitted by an HVDC cable like those already in US waters decreases with distance from the cable and never exceeds the strength of the Earth’s magnetic field. This means that it is essentially impossible for the magnetic field itself to be harmful to marine life, although the studies described above indicate that some species can detect it. Scientists in both the U.S. and Europe are investigating whether the observed changes in individual behavior translate into significant impacts at the population level of a species. Research is ongoing to inform how wildlife detect and respond to these fields but, at this point, the studies have thus far concluded with reasonable confidence that the EMF levels emitted from offshore wind cables are unlikely to cause significant risk to marine species.
An excellent summary article from BBC with links to research is How Undersea Cables May Affect Marine Life.
A Deeper Dive:
Are EMFs evaluated as part of the review process for permitting offshore wind?
Yes, EMFs are considered during the environmental review process. In the United States, EMFs are described in Environmental Impact Statements and Construction and Operations Plans, which must cite the burial depth, cable shielding, and limited range of EMFs as factors that contribute to a highly localized environmental condition that does not affect the entire habitat range for an animal. In this way, standards are upheld across all offshore wind operations.
For a more complete description and illustrations of these cables, including original references about marine species behavior around EMFs, visit the Sea Grant Energy website:
www.seagrantenergy.org/liaison-updates/effects-and-impacts-of-emf-radiation and https://tethys.pnnl.gov/sites/default/files/summaries/SEER-Educational-Research-Brief-Electromagnetic-Field-Effects-on-Marine-Life.pdf
Understanding Complexities:
Whenever we transport power from a power plant of any type, we use high voltage cable to reduce the energy lost during transmission. By raising the voltage, we can lower the current lost during transmission. The cables are designed to reduce the electric current as they come on shore, keeping the power at an appropriate level. Electric current is what generates the magnetic field, so by reducing the current for a high-voltage cable, the EMF (electric magnetic field) ends up being about the same as a regular power line that you’d see running alongside roads.
It is important to remember that for human health, the high voltage cables undersea cables are entirely inaccessible , in contrast to those already existing to carry power from on-shore power plants. While EMFs are generated by undersea cables, those same EMFs are also generated by the high voltage cables running across the country over land right now. Given this, the risk from offshore wind cables is much smaller than that from existing onshore power structure
These EMFs may inspire questions around health risks and exposure. According to the World Health Organization, potentially carcinogenic substances have four different categories:
Type 1 means definitely carcinogenic,
Type 2a means probably carcinogenic,
Type 2b is possibly carcinogenic (inconclusive, some correlations but causation isn’t proven),
Type 3 is no evidence of being carcinogenic,
Type 4 is not carcinogenic.
EMFs fall under 2b, which is the same classification as given to cell phones.
The NIH National Cancer Institute Website defines EMFs from power lines as Extremely Low Frequency-EMFs (ELF-EMFs). It states, “No mechanism by which ELF-EMFs or radiofrequency radiation could cause cancer has been identified. Unlike high-energy (ionizing) radiation, EMFs in the non-ionizing part of the electromagnetic spectrum cannot damage DNA or cells directly. Some scientists have speculated that ELF-EMFs could cause cancer through other mechanisms, such as by reducing levels of the hormone melatonin. There is some evidence that melatonin may suppress the development of certain tumors. Studies of animals have not provided any indications that exposure to ELF-EMFs is associated with cancer (10–13). The few high-quality studies in animals have provided no evidence that Wi-Fi is harmful to health.”