The Obama Administration has put a premium on good science in environmental policy, but some folks in the Navy don't seem to have gotten the message.
In a study soon to be published in Biology Letters, researchers exposed a captive bottlenose dolphin to recordings of Navy sonar and then gave the animal a hearing test, to see whether it suffered hearing loss. In fact, the study is the latest in a line of similar experiments that the Navy has sponsored, usually on bottlenose dolphins since the Navy maintains several of the animals in captivity. In this case, it took higher sonar levels to produce hearing loss in that one animal than might have been predicted from earlier studies.
That's useful to know, and it adds to our existing knowledge about sonar's effects on marine mammal hearing. The problem is that the Navy, hungry for any science that might justify its recalcitrance on sonar policy, wants it to mean a lot more than it says.
Simply put, studies of hearing loss like this one don't address the central concerns that scientists have about sonar: its widespread impacts on marine mammal behavior, its long-term effects on marine mammal health, and its startling capacity to injure and kill certain species of whales.
Let's take mortalities first. Deep-diving beaked whales - exposed to levels of sonar much lower than those needed to cause hearing loss - have consistently turned up with hemorrhaging in their brains and emboli in their livers and other organ tissue. The leading theory is that Navy sonar drives them to alter their highly-evolved dive patterns in ways that induce "bends"-like injuries. This view is supported by multiple peer-reviewed articles on dive physiology, tissue pathology, and other subjects. And while a number of other mechanisms remain possible (an expert workshop organized by the U.S. Marine Mammal Commission identified several), hearing loss is not among them.
How to prevent these injuries is a deadly serious problem given that beaked whales make up one-sixth of all marine mammal species on earth. But the new study doesn't move us any closer to a solution and, quite reasonably, doesn't attempt to.
Nor does the new study contribute to our knowledge of an even more important problem: sonar's impacts on whale behavior. Navy sonar is known to cause whales and other marine mammals to stop vocalizing and feeding, to abandon habitat, to panic, to put themselves at risk of ship collision, and, in some cases, to strand and die. These impacts occur in some species at very low levels of sonar exposure and affect vast numbers of animals. Even the Navy estimates that its exercises off the coastal United States would significantly impact marine mammals more than 2 million times each year. All of these behaviors may be critical to survival, not just of individual animals but of entire populations, many of which are already endangered or depleted.
The new study has little, if anything, to say about these critical behavioral effects, and rightly so. "Boris," the dolphin used in the experiment, wasn't a wild animal or even an ordinary captive animal, but one that was specifically trained for years to stay on task during experiments.
But that won't stop the Navy from spinning the study as though it were some Archimedean lever displacing years of research on completely different issues. Hopefully, the press will put on the brakes.