On Friday a federal appeals court overturned a 2012 ruling which allowed the U.S. Navy to use sonar for training, testing and routine operations. The low-frequency sonar employed by the Navy has been shown to harm dolphins, whales and other marine mammals.Friday s decision came in response to a lawsuit filed by the Natural Resources Defense Council, which was later joined by environmental groups. The suit alleged that the lower court s decision to allow the use of sonar was a direct violation of the Marine Mammal Protection Act.The court agreed that the Navy s use of sonar in the Atlantic, Pacific, Indian Oceans and the Mediterranean Sea violates a section of the Act which requires all peacetime Oceanic operations to have the least practicable adverse impact on marine mammals. The court also found that guidelines set forth by the U.S. Fisheries Service did not give adequate protection to areas of the world s oceans flagged by its own experts as biologically important.  The court found the result to be that  a meaningful proportion of the world s marine mammal habitat is under-protected. As Scientific American reports here:Unfortunately for many whales, dolphins and other marine life, the use of underwater sonar (short for sound navigation and ranging) can lead to injury and even death. Sonar systems first developed by the U.S. Navy to detect enemy submarines generate slow-rolling sound waves topping out at around 235 decibels; the world s loudest rock bands top out at only 130. These sound waves can travel for hundreds of miles under water, and can retain an intensity of 140 decibels as far as 300 miles from their source.Studies show that the use of sonar can cause whales to swim hundreds of miles and even beach themselves in an attempt to get away from the sound. The use of sonar can also cause marine mammals to bleed from their eyes and ears. It can also cause temporary deafness, a condition which leaves animals vulnerable to predators and other threats. According to the Navy s own estimates, the use of low frequency sonar is expected to kill 170,000 marine mammals and cause permanent injury to more than 500 whales. An additional 8,000 would experience temporary deafness.The latest ruling, which bans the use of sonar entirely, is a huge victory for environmental and animal rights activists.Image credit: Whit Welles via Wikipedia cc 3.0