Low-frequency active (LFA) sonar systems used in areas covering 70 percent of the world's oceans are harming marine life population, a federal appeals court ruled.

The Ninth Circuit Court of Appeals in California determined that the use of LFA sonar systems violates the Marine Mammal Protection Act and negatively affects dolphins, seals, whales and walruses that depend on underwater sound for navigation.

The Navy will no longer be permitted to use LFA sonar systems to detect the presence of submarines.

The ruling finds that the National Marine Fisheries Service (NMFS), which gave the clearance for the Navy to use LFA, has to put more efforts to avoid the damage and destruction of marine environments and populations.

Indeed, environmental advocates say that the sonar systems disrupt the feeding and mating of marine animals that rely on sound to catch prey and communicate.

In 2012, the NMFS allowed the use of navy sonar, but this five-year plan was delayed or shut down when a marine animal was detected close to the ships. Loud solar pulses were banned in protected waters and near coastlines.

The Natural Resources Defense Council (NRDC) had filed a lawsuit in response to the 2012 incident, claiming the NMFS approval violated laws.

The federal appeals court determined that approval failed to meet a section of the Marine Mammal Protection Act that required the program to have the "least practicable adverse impact on marine mammals."

The appeals court said the Navy attempted to follow guidelines, but it concluded that the agency did not provide "adequate protection" to areas considered as biologically and ecologically important.

The court concluded that a significant proportion of marine mammal habitat across the world is under-protected.

Experts say the navy sonar systems can generate sound waves as high as 235 decibels. In comparison, a loud rock band reaches around 130 decibels.

Sound waves from sonar systems can travel for hundreds of miles underwater and can maintain an intensity of 140 decibels as far as 300 miles (482 kilometers) from the source.

Although there are no studies that prove direct correlation, some researchers believe that sonar use has altered the behavior of whales, which have been found to be swimming away hundreds of miles. In consequence, the whales rapidly change their depth and become at risk of beaching themselves.

According to the NRDC, the NMFS' five-year plan lead to 155 mortalities and 9.6 million cases of temporary injury of marine life.

Photo: Jose Antonio Navas | Flickr