The U.S. Navy and a federal agency charged with protecting ocean life haven't done enough to make sure tests of experimental sonar won't hurt marine mammals, a federal appeals court ruled late last week. The ruling is a bit of a reprieve for marine mammals, which stand to suffer significant potential harm from this obscure aspect of American foreign policy.
The Navy intends to tow 18 underwater loudspeakers 100 meters below the surface of the ocean in the Atlantic, Pacific, and Indian oceans, along with the Mediterranean Sea, to test new ways of detecting increasingly quiet submarines operated by potentially unfriendly nations. The tests, which would take place over a five-year period, are part of the Navy’s so-called “surveillance towed array sensor system low-frequency active sonar” program, an imposing name with the equally imposing acronym SURTASS LFA.
Those loudspeakers would emit very loud pings – around 230 decibels – that will bounce off of solid underwater objects. The echoes will be picked up by SURTASS LFA’s microphones, and computers will analyze the echoes to determine whether any of those echoing underwater objects are enemy submarines. The eventual goal, according to the Navy, is a global submarine detection network with which the United States can track submarines and other ships in all the world’s oceans. The testing would expose almost three-quarters of Earth’s oceans to those loud pings.
Critics charge that those pings could wreak havoc on the world's beleaguered marine mammals, and possibly other sea life as well. The project's most vocal opponents are breathing a collective sigh of relief at a Friday ruling by the Ninth Circuit Court of Appeals that the federal government violated the Marine Mammal Protection Act in approving the tests.
At issue, claims the Navy, is the United States’ ability to detect relatively quiet diesel-electric submarines in an increasingly loud ocean. The Navy has long relied on so-called “passive sonar” – a.k.a. “listening” — using a network of seabed microphones. Computers sort out the enemy sub noise from random ship traffic and other confounding sounds. As the oceans get noisier, claims the Navy, it’s harder and harder to sort out the subs from the container ships and oil tankers.
That justification for the project has remained unchanged since the 1990s, though the Navy has access to computer processing power orders of magnitude more powerful than it did during the Clinton administration. Critics have pointed out that passive sonar works as well as it ever has in the open ocean: it’s along coastlines, where underwater sound echoes off the complex shallow seabed and rocky shore, that passive sonar can falter. And since the U.S. Navy could thus track any attacking diesel-electric submarines long before they reach the U.S. coast, as their silent electric mode can only be used for relatively short distances, some analysts have suggested that active sonar such as SURTASS LFA is primarily useful along the coasts of hostile countries the United States is attempting to invade, where those diesel electric subs might be lurking close to home, in defense mode.
And indeed, that's how SURTASS LFA was described in defense trade journals throughout the 1990s; as a tool for use in naval campaigns during U.S. interventions overseas.
How do whales figure into this geopolitical weapons technology issue? Noises as loud as those used by the SURTASS LFA program have been shown to cause potentially fatal injury to marine mammals at short range. The pings’ effects on more distant wildlife is not yet settled, though marine mammal advocates point out that seriously injured marine mammals have stranded themselves after regional sonar tests in a number of places over the last couple of decades.
That brought the U.S. Marine Mammal Protection Act (MMPA) into play. In order to conduct its tests legally, the Navy needed clearance from the National Marine Fisheries Service (NMFS), the agency charged with enforcement of the MMPA and other marine wildlife law. If NMFS found that the Navy’s plan posed an unacceptable risk to protected marine mammals, the Navy would have had to head back to the drawing board. But in 2012 NMFS signed off on the Navy’s test plan, saying that the Navy had agreed to measures that would protect wildlife from harm caused by the project. Among those measures were agreements to stay more than 12 miles from coastlines, and to avoid “offshore biologically important areas” identified by NMFS.
Those measures didn’t reassure environmental and wildlife protection groups, a number of which sued NMFS in an attempt to force the agency to reconsider. The Natural Resources Defense Council and its co-plaintiffs charged that NMFS hadn’t lived up to its responsibility to protect marine mammal habitat from SURTASS LFA in the vast majority of the ocean habitats that would be subjected to loud noise during the tests. NMFS designated just 73 of those offshore biologically important areas in its review of the SURTASS LFA project, saying that there wasn’t enough known about marine mammal presence in other parts of the oceans to justify protecting their habitat. NRDC and its co-plaintiffs argued that absence of data for unprotected parts of the ocean didn’t mean absence of marine mammals – a position that some NMFS scientists had also argued before their agency’s decision.
The green groups and the Navy each have scientists that support their cases. But it makes sense that very loud noise in the ocean would pose a serious risk to animals that primarily navigate, communicate, and find food using the same technology as SURTASS uses to find ships. Whales and dolphins emit noises, then use their incredibly sensitive hearing to read the reflected sound waves. Tests have shown that bottlenose dolphins can tell the difference between cubes and spheres of similar size using just their hearing. It’s been conjectured that whale song sung by animals in the North Atlantic near Newfoundland can be heard by whales in the Caribbean. Humpback whale mothers can recognize their calves’ voices from miles away, and vice versa.
The Navy claims that farther than a nautical mile from the SURTASS loudspeakers, the pings drop below 180 decibels and thus don’t pose a long-term threat to whales or other marine mammals. While sounds of 180 decibels are dangerously loud when we’re talking about a human listener and sounds traveling in air – we can suffer permanent hearing loss from short exposures to sounds of 170 decibels -- it’s risky to extrapolate to cetacean ears listening underwater. Loud sounds underwater may travel much farther, but they can exert less force on sensitive ears and other tissues as a comparably loud air-borne sound might.
And then there’s accounting for the differences in human and cetacean ears, the latter of which are clearly evolved to be remarkably sensitive underwater. It’s no wonder that you can find scientists on several different sides of the issue of potential harm to wildlife from sonar. It's worth noting, though, that the Navy has set an upper limit on underwater noise to which Navy divers can be safely exposed. That limit is 140 decibels. The decibel scale is logarithmic: a sound at 150 decibels is ten times louder than one measuring 140 decibels. Which means the Navy is claiming that marine mammals can safely withstand noises ten thousand times louder, at 180 decibels, than it will allow its own divers to experience.
There's at least one aspect of this that isn't at all controversial: No one disagrees that marine mammals rely utterly on their amazingly sensitive hearing for almost all aspects of their daily life. If loud sonar pings cause permanent hearing loss, that can doom the whale to a slow, unpleasant demise. Even a temporary hearing loss can dissuade whales from using formerly useful habitat, if they associate the place with being unable to hear. And loss of habitat definitely qualifies as harm prohibited under the Marine Mammal Protection Act. In its approval of the Navy’s tests, NMFS says that no more than 12 percent of any protected marine mammal species can be subject to that kind of disruption of breeding, feeding, and migration.
It was a procedural error that torpedoes NMFS' approval of SURTASS LFA last week. According to the language of the Marine Mammal Protection Act, NMFS can only permit activities that risk harming marine mammals if the amount of harm done is “negligible,” and steps are taken to mitigate that damage to the “least practicable adverse impact” – in plain English, the least amount of harm that can reasonably be achieved. Both the “negligible impact” requirement and the “least practicable adverse impact” requirement must be met for NMFS to approve a potentially harmful project.
On Friday, the Ninth Circuit Panel found that while NMFS had arguably met the first of those two conditions in declaring that SURTASS LFA would have a negligible impact on marine mammals, the agency had failed to meet that second condition – it hadn’t required the Navy to take more reasonable steps to reduce the project’s hazard to wildlife.
And so SURTASS LFA heads back to the drawing board. It's not a death blow to the project, which has suffered similar setbacks in the nearly three decades since it was first declassified. But it does offer a little bit of breathing room for marine mammals, which already have enough problems to contend with.