The US Navy's use of sonar violated maritime laws, the US Court of Appeals has ruled.
Active low-frequency sonar, approved in 2012, is used to detect enemy submarines. But it can also harm whales, dolphins and elephant seals that rely on underwater sound to move, find prey and communicate, according to environmental groups.
The case will now be sent back to a lower court for further consideration.
In 2012, the National Marine Fisheries Service allowed the use of marine sonar, but required it to shut down or delay use when a marine mammal is detected near ships. The powerful sonar pulses were also banned near shore and in some protected waters.
Environmental groups, led by the Natural Resources Defense Council, filed a lawsuit in response, claiming the approval violated the Marine Mammal Protection Act.
The San Francisco federal appeals court ruled that the approval rules granted to the U.S. Navy failed to meet a section of the protection law that requires the program to have “the least possible adverse impact on marine mammals.”.
While he initially believed the Navy had attempted to follow the guidelines, he concluded that the fisheries service “is not providing adequate protection to areas of the world’s oceans that have been identified by its own experts as biologically significant.”
According to experts, sonar systems used by the navy produce sound waves that can reach 235 decibels – a loud rock band reaches about 130. These sound waves can travel for hundreds of miles underwater and can maintain an intensity of 140 decibels up to 300 miles away from their source.
Although direct correlations are difficult to find, some scientists believe that the use of sonar has changed the behavior of whales who have been observed swimming far away, sometimes hundreds of miles, rapidly changing their depth.
