For years, conservation groups and the US Navy have been involved in an intricate dance concerning the application of provisions of the Marine Mammal Protection Act (MMPA) to Navy activities. The goal of the conservationists has been to get the Navy to agree to restrictions on its acitivities as the MMPA would do for any civil entity, but not press so hard that the Navy simply disengages and declares itself ungoverned by the MMPA.
An item on the MARMAM email list indicates that the dance may be over. According to Michael Jasny at the Natural Resources Defense Council (NRDC), the US Navy has taken the step of issuing itself a two-year exemption from provisions of the MMPA in order to continue training using mid-frequency (2 to 10 kHz) sonar systems. I’ve requested a couple of documents from Jasny about this issue; I’ll update when I get those.
Military use of mid-frequency sonars causes morbidity and mortality in beaked whales under certain conditions. A mass stranding of beaked whales in the Bahamas in 2000 caused the National Marine Fisheries Service to conduct a workshop in 2002 bringing together experts on biology and acoustics to evaluate the acoustic resonance hypothesis for this morbidity and mortality. While the acoustic resonance hypothesis was considered unlikely by us, we did broadly agree that the evidence indicated a correlation between military exercises using mid-frequency sonar and mass strandings of beaked whales. The historical record, once examined with military exercises in mind, showed concomitant beaked whale mass stranding events going back to at least 1963. What remains at issue is what, precisely, is the mechanism of the morbidity and mortality of beaked whales exposed to military mid-frequency sonar, which would allow military planners to avoid the set of circumstances that would endanger beaked whales. In the absence of knowledge about the mechanism, though, what can be done is to look at past beaked whale mass stranding events that occur in the presence of mid-frequency sonar and attempt to correlate common factors.
Or, as various groups have urged, the Navy can discontinue use of mid-frequency sonar entirely. This latter approach I speculate is the proximal cause of the US Navy deciding that it would simply remove considerations of the MMPA from its planning in the use of mid-frequency sonar.
Update: I’m looking at some of the news coverage on this topic, and I keep seeing a phrase of the sort that says that mid-frequency sonar is “harmful to whales”. This sort of statement is misleading. The harm caused by mid-frequency sonars is only definitively demonstrated to occur in beaked whales, one taxon of toothed whales, not whales in general, which is the likely reading that many will take away from the news reports. There is something very specific about the vulnerability of beaked whales to the operation of mid-frequency sonars that is not generally shared even with other, more familiar, odontocetes.