The Defense Department has exempted the Navy and its use of sonar from the federal Marine Mammal Protection Act for two years — causing an outcry from a national environmental group that maintains the underwater sound harms whales.

Last summer, a six-month exemption granted during biennial Rim of the Pacific, or Rimpac, naval exercises off Hawai'i led to a legal challenge, and a federal judge briefly prohibited midfrequency sonar use during the war games.

Rimpac is one of the largest naval exercises in the world, and last year involved eight nations, more than 40 ships, six submarines, 160 aircraft and almost 19,000 service members.

The new two-year exemption is the latest turn in an ongoing battle that has pitted environmentalists and emerging science on the harm of sonar to whales against the Navy's need for sonar training to detect a growing fleet of extremely quiet foreign diesel submarines.

The next court clash could come over expected Navy sonar use off the coast of California, but the Defense Department exemption would extend through the 2008 Rimpac exercises off Hawai'i.

Federal marine regulators last spring said sonar use was a "plausible, if not likely, contributing factor" in the stranding of up to 200 melon-headed whales off Kaua'i during July 2004 Rimpac war games.

The mass stranding of such whales was the largest recorded in Hawai'i waters, but the science related to sonar impact on various types of marine animals is far from clear-cut.

"The Navy's position is that continued training with active sonar is absolutely essential in protecting the lives of our sailors and defending the nation," the Pentagon said yesterday in announcing the exemption.

PROTECTION EFFORTS

The Defense Department also said the Navy continues to work with the National Oceanic and Atmospheric Administration, or NOAA, on a long-term sonar-use plan, and a range of marine mammal protection measures will remain in place.

"We will continue to employ stringent mitigation measures, developed with NOAA's concurrence, to protect marine mammals during all sonar activities," said Rear Adm. James Symonds, director of environmental readiness for the Navy.

But the Natural Resources Defense Council, which filed suit against the Navy in 2005 over midfrequency sonar use, said "numerous" mass strandings and deaths have been associated with sonar use.

Joel Reynolds, a senior attorney and director of the Natural Resources Defense Council's Marine Mammal Protection Project, objected to the exemption from federal law.

"Obviously, the (Marine Mammal Protection Act) is a statute that is designed to protect marine mammals," Reynolds said. "When you nullify that, there's no getting around the fact that they are undermining the protection that federal environmental law provides."

Reynolds said the Navy has "more than enough room in the ocean to train effectively without injuring or killing endangered whales and other marine species," but chooses some locations because of their convenience.

PERMIT TO 'HARASS'

Responding to growing scientific evidence that sonar can disrupt, injure or kill whales or dolphins, the Navy for the first time last summer sought a federal permit under the Marine Mammal Protection Act to "harass" the sea creatures when it uses midfrequency sonar during Rimpac.

After NOAA Fisheries granted the permit, environmental groups sued to try to stop it. The Defense Department stepped in, said national defense concerns pre-empted the act, and granted a six-month exemption.

A federal judge subsequently said other environmental laws still applied and ordered the Navy and environmental groups to negotiate.

SAILORS ON LOOKOUT

Among the protections the Navy agreed to undertake were to not use sonar within 25 miles of the Northwestern Hawaiian Islands Marine National Monument, and to report the presence of marine mammals detected through underwater listening devices or visual scanning.

The Navy also posted one person per ship whose job it was to search the waters for marine mammals during the exercises, and three others keeping an eye out.

Instead of applying for federal permits to "harass" marine animals for each and every sonar exercise, the Navy wants to conduct environmental impact analyses for "bodies of water."

"We did it (individually) for Rimpac, and that was kind of the example of, 'This isn't going to work,' " said Lt. Ryan Perry, a Navy spokesman at the Pentagon.

Reynolds said the Navy can accomplish some of its sonar training at locations such as the Pacific Missile Range Facility ocean areas, "but the way they've done it historically is to train all over the Hawaiian Islands, and inside of sanctuaries, really without regard to environmental harm. I think that's a mindset that has to change."

Reach William Cole at wcole@honoluluadvertiser.com.