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May 1, 2006

Sonar Strandings & Dolphin Deaths

We're planning to spend part of our honeymoon on Zanzibar, so I keep pretty close tabs on the news of the area. The little island off the coast of Tanzania is known for its beautiful beaches and spectacular diving. This past week, there are been some very sad news for the area as a large number of dolphins washed up dead on the north shore of the island for reasons "unknown".

Villagers and fishermen on Saturday buried the remains of the roughly 400 bottlenose dolphins, which normally live in deep offshore waters but washed up Friday along a 2.5 mile stretch of coast in Tanzania's Indian Ocean archipelago.

...

A U.S. Navy task force patrols the coast of East Africa as part of counterterrorism operations.

More at: MSNBC: Sonar tied to deaths of 400 dolphins?

Whale and dolphin strandings happen for a variety of reasons. Sometimes the animals have been poisoned. In this case, the dolphins had empty stomachs, which rules that out for the most part. Recently, more and more strandings have been attributed to sonar. Specifically, military active sonar, low frequency or mid-spectrum sonar, employed almost exclusively by the military.

Can Active Sonar Really Hurt Marine Life?

At this point, the answer is yes. Although the U.S. military doesn't seem to wish to accept this reality, the evidence is pretty conclusive at this point. The Scientific Committee of the International Whaling Commission is made up of 200 of the world's leading whale biologists. Their recent report claimed evidence linking active sonar to whale strandings is "very convincing and appears overwhelming."

How Does Military Active Sonar Hurt Marine Life?

Now, we're not talking the little fish finders on fishing vessels here. We're talking long-range military active sonar. The type of sonar that sends huge, powerful sound wave booms through tens or hundreds of miles of ocean.

Each loudspeaker in the LFA system's wide array, for example, can generate 215 decibels' worth -- sound as intense as that produced by a twin-engine fighter jet at takeoff. Some mid-frequency sonar systems can put out over 235 decibels, as loud as a Saturn V rocket at launch. Even 100 miles from the LFA system, sound levels can approach 160 decibels, well beyond the Navy's own safety limits for humans.

More at: NRDC: Protecting Whales from Dangerous Sonar

The prominent science journal Nature has published numerous findings on the effects of active sonar on marine mammals. The current reasoning is that the active sonar "confuses" the marine mammal's echolocation abilities, causing them to strand themselves. While this might be true of animals receiving weak signals from great distance, I tend to think that "confusing" is a rather watered down term when the poor creatures are bleeding in the ears and brain. Frankly, it sounds more like a case of rendering a creature dependent on sound deaf and terrified with great booms of noise.

Pathology evidence of stranded whales has shown that they have suffered from embolisms, or nitrogen bubbles in their tissue. Much like divers who ascend too quickly can get "the bends" and die, the marine mammals appear to suffer from a similar condition after being hit by the deafening sound waves. They panic and surface too quickly.

Those that survive often suffer from other, more subtle changes in behavior whose damage is much more difficult to measure. Just searching for "active sonar" on Nature.com turns up some interesting examples, like how whale songs, a key part of courting and mating rituals, are changed after the whales are exposed to the sonar noise.

Marine mammals use sound to navigate, to communicate with mates and young, and to find food. Military sonar has been shown to disrupt these key activities and over time, the health of marine mammal populations. The long-term effects are just not yet known.

Have There Been A Lot Of Marine Mammals Injured?

It's very difficult to determine how many whales and dolphins have been killed or injured by the use of active sonar because it's likely that only a small percentage of the animals wash up on beaches to be counted. Many animals may just drown in the deeper waters in which they live and we wouldn't know it other than by their absence.

One of the first clear-cut cases of active sonar harming whales was back in March of 2000 when a U.S. Navy battle group was using active sonar off the Bahamas. Four different species of whales became stranded on the beaches of the Bahamas. Post-mortem analysis found that the whales were bleeding internally around their brains and ears. Although the Navy initially denied any responsibility, the subsequent government investigation proved otherwise. Since then, many other strandings have been tied back to military activities and active sonar usage. So far, thousands of marine mammal deaths have been attributed to active sonar use.

And these are just the ones we can count.

What's Being Done?

Back in 1994, the National Resources Defense Council (NRDC) investigated rumors of active sonar experiments being conducted off our own California coast, a well-established whale migration route. The rumors proved to be true. Conservation organizations like the NRDC are continually lobby to limit use of active sonar in the world's oceans. Governmental agencies like the EU and NATO have been petitioned with some success. Some countries have already begun to phase out use altogether, or at least limit it where it will do the most harm. The United States has been hesitant to follow suit, despite the overwhelming evidence.

Conservationalists argue that where the technology cannot be abandoned entirely for security reasons, then at least it can be used judiciously. By avoiding key marine habitats like migration routes, breeding areas, and marine reserves, the negative effects of active sonar can be minimized, at the very least. Passive sonar (listening but not transmitting) can also be used to determine if marine mammals are in the area before using active sonar.

Still, for every positive step forward, it seems a road block arises. A federal court ruled the Navy's plan to deploy LFA sonar through 75 percent of the world's oceans illegal in 2003, in violation of the Marine Mammal Protection Act, the Endangered Species Act, and the National Environmental Policy Act. The Navy and conservationalists came to a compromise: judicious usage of active sonar with regard to marine life with flexibility for training exercises. None of the limits applied during war or high threat conditions and the agreement was considered a good balance of environmental protection and national security. The Bush Administration didn't agree. They followed up by exempting the U.S. military from core provisions of the Marine Mammal Protection Act. Now the administration is appealing the ruling limiting deployment of LFA sonar.

Dead Dolphins In Zanzibar

With no food in their bellies, it seems unlikely that the dolphins that washed up this past week were poisoned. Eastern African countries like Kenya, Tanzania and Somalia have seen recent and continued Al-Qaeda activity, so it's not surprising to have an active military precence in the area. Banging away on active sonar, no less. National security is, therefore, a real concern here. But still, there is a cost to active sonar use that needs to be communicated to the public, understood, and considered when determining acceptable losses in decision making. These choices have a significant impact on our planet.

Posted by sorsha at May 1, 2006 1:45 AM