The US Navy has been barred from using its mid-frequency sonar systems in naval exercises off of southern California. The Natural Resources Defense Council sought the injunction.
The reporting on this issue has improved over time. It used to be that reporters did not distinguish between different sonar systems, and various environmental groups exploited that vagueness to argue that “Navy sonar” harmed cetaceans. Some sonar systems deployed by the US Navy, and other navies around the world, do have a record of harming certain taxa of cetaceans, but others do not. The article leads off,
A federal judge on Monday ordered the Navy to stop using medium-range sonar in training exercises off Southern California, saying that the Navy’s own assessments predicted that dozens of marine mammals, particularly deep-diving whales, could be harmed by the intense sound waves.
There are two apparent vaguenesses or inaccuracies in the above. It is unclear whether the reporter introduced them, or simply passed them on from a confused court. There is the distinction made about “medium-range sonar”; this is an odd way to refer to mid-frequency sonar systems, which are the ones implicated in various stranding incidents involving cetaceans. Then there is the “predicted that dozens of marine mammals, particularly deep-diving whales, could be harmed” part of the sentence. Does this refer to the number of individuals, and under what circumstances does that prediction hold? How many different species might be included? The previous sonar-related stranding incidents showed a particular sensitivity of whales in the genera Ziphius and Mesoplodon (the beaked whales, which are deep divers); are these the ones referred to here? It’s tough to tell.
There’s something else odd in the article. Consider these two paragraphs,
The Navy has argued that without training on this widely used system, sailors’ ability to detect enemy vessels is severely hampered. Active sonar, at various frequencies, has been developed over the past two decades as diesel engines on military craft became quieter and harder to detect with passive sonar.
Donald R. Schregardus, deputy assistant secretary of the Navy for the environment, said, “The decision puts sailors and marines at risk by ordering the Navy to stop critical antisubmarine warfare training while we complete environmental impact statements on our training ranges.”
Active sonar used for sinking subs dates back to World War II. Now, I doubt that any of the systems developed then are still in use by the US Navy, but “active sonar” as a class of equipment does have a much longer history. In fact, one of the beaked whale mass stranding events associated with mid-frequency sonar was back in the early 1960s (1962 or 63, IIRC), which considerably predates “over the past two decades”. But the real stinker in the first of those quoted paragraphs is, “as diesel engines on military craft became quieter and harder to detect with passive sonar”. That, coupled with the topic identified in the second paragraph of “antisubmarine warfare”, indicates massive confusion somewhere in the construction of the article. First off, most of the submarines of interest don’t use diesel engines. Unless we are concerned about Brazil’s submarine fleet, we aren’t primarily trying to detect the presence of diesel-powered subs. What has gotten much better in the way of submarine running gear is the propeller. Remember the flap over Toshiba trading with the USSR? What the USSR got was computer-controlled machining equipment that would allow them to manufacture submarine propellers to extremely fine tolerances, reducing cavitation and turbulence, and thus making their subs much, much quieter. That’s why the Navy has an interest in active sonar systems.