The Virginia-class USS North Dakota (SSN 784) submarine is seen during bravo sea trials in this U.S. Navy handout picture taken in the Atlantic Ocean August 18, 2013. The Navy commissioned its newest attack submarine North Dakota, during a ceremony October 25, 2014, at Submarine Base New London in Groton, Connecticut, defense officials announced. (U.S. Navy/Reuters)

No humans will be harmed in the war games the Navy is conducting in the Pacific Ocean near California and Hawaii for the next four years.

The same cannot be said for marine mammals that gather there. Dozens of blue whales, bottlenose dolphins and seals are almost certain to die, and tens of thousands more could be permanently injured by explosives and underwater sonar.

War games have played out in the vast Hawaii-Southern California Training and Testing Study Area for nearly 45 years, and environmentalists again are trying to halt them. The Conservation Council for Hawaii filed a federal lawsuit last year before the start of the exercise and last week submitted a motion asking a judge to declare the training illegal because it violates an act meant to protect endangered mammals.

This argument has found its way in federal courts numerous times, with the U.S. Supreme Court siding with the Navy in a 2008 case, saying sacrifices must be made in the military’s quest to protect the public.

The question is how many lives of endangered whales and seals, along with depleted stocks of dolphins, is too many.

Excruciating noises are in store this winter for whales calving off the coasts of Hawaii and California.

Through 2018, the Navy plans to use 260,000 explosives — some as heavy as 2,000 pounds — and emit high-frequency sonar for a total of 500,000 hours — including 60,000 hours of the most powerful sonar.

A single “ping” generated every 10 seconds can permanently damage the ears of animals that rely on hearing to find food in the deep ocean, according to conservation groups that filed a lawsuit challenging the operation. There is no threat unless animals are within 100 meters of a ping.

In the lawsuit, attorneys for two nonprofit environmental groups that represent the council in Hawaii, Earthjustice and the Natural Resources Defense Council, say the Navy is conducting “more intense training” that violates an act to protect marine mammals and should not have been permitted by the National Marine Fisheries Service, a division of the Department of Commerce charged with protecting mammals.

They claim that the fisheries service “rubber stamped” a permit the Navy needed to conduct the exercise, failing to consider the full impact on numerous species under its protection. That animals should die for the common good is not in dispute, the lawyers said, but the current exercise will take too many.

“The more we look at the Navy’s activities, the more we’re finding the potential for harm,” said Michael Jasny, the director of NRDC’s marine mammal protection project. Citing the Navy’s estimates, he said the impact of the current exercise on animals will “increase more than 11 times over the previous five-year period.”

The fisheries service declined to comment, citing the pending lawsuit. But the Navy emphatically denounced the activists’ characterization of their operations.

In an environmental impact statement that the fisheries service requires as part of the permitting process for the exercise, the Navy estimated that the exercises would result in 155 deaths of marine mammals, 2,000 permanent injuries and nearly 10 million instances of temporary hearing loss and disruptions of behavior.

An adult, female beaked whale swims off the Kona coast in Hawaii. These and other marine life are at the center of a dispute over the Navy's use of sonar, missiles and machine guns. (Robin W. Baird/Cascadia Research Collective/Associated Press)

Conservation lawyers seized on those numbers to describe the harm, but the Navy called that unfair. They “are not annual numbers but actually cover a five-year period” and “represent worst-case scenarios,” said Kenneth Hess, a spokesman for the Navy.

“Despite decades of the Navy conducting very similar activities in these same areas, there is no evidence of these types of impacts,” Hess said. Permits the Navy requires for the training “can only be issued if our activities will have no more than a negligible impact on marine mammal populations,” he said.

That assessment was backed by Brandon Southall, a former fisheries service researcher who researches at the University of California at Santa Cruz. “I think the numbers” citing potential harm presented by the Navy and NMFS “are overestimates,” he said.

“Overall, I think the concerns are being amplified because the conservation groups are interested in getting people’s attention, and they get it by saying these animals are all going to die,” Southall said.

“This is where the Navy is kind of damned if they do and damned if they don’t,” he said. “If you assume the worst-case scenario, using models that have different levels of uncertainty. . . you wind up getting really high numbers. They get these large numbers and they get sued.”

The lawsuit appears to face an uphill battle, if previous court rulings serve as a precedent.

In Winter v. Natural Resources Defense Council , the court decided that the military’s interests trumped environmental concerns, lifting an injunction against training with sonar imposed by a lower court.

Activists say the pending case is different because the mortality estimates in the impact statement exceed the numbers allowed under the federal Marine Mammal Protection Act.

They said the fisheries service failed to analyze the consequences of the deaths that could happen in the next four years, according to the Navy’s analysis, and failed to take basic steps to mitigate damage, such as instructing the Navy to avoid certain sensitive areas when animals are feeding, mating and giving birth.

“No one is suggesting the Navy shouldn’t be allowed to do testing and training,” said David Henkin, a staff attorney for Earthjustice. ‘The question is whether they need every inch of the ocean. . . particularly biologically significant small refuges.

“We’re saying that even if you take their own numbers, they’re so monumental, it violates the animal protection act,” Henkin said. “They cannot justify it.”

The Navy’s use of sonar is central to the legal complaint. Its effect on marine mammals is widely debated, but recent incidents have left no doubt that it can be harmful to animals .

Conservationists compared the high-frequency decibel levels of mid-range sonar to the sound of 2,000 jet engines.

In April this year, several Cuvier beaked whales stranded on the beach and died on the southern coast of Crete in Greece when the United States conducted war games with two other countries’ navies. In 2000, four species of whales — 16 in all — beached themselves in the Bahamas during Navy exercises.

At first, the Navy denied responsibility in the Bahamas. A U.S. government investigation proved otherwise. Afterward, beaked whales in the area nearly disappeared.

Sonar-related strandings also have occurred in the Canary Islands, Virgin Islands, the Outer Banks of North Carolina, Washington state and Alaska.

Jasny said the sonic activity alone can disrupt the behaviors of blue whales and beaked whales “in millions of instances,” causing them to flee, stopping them from eating, communicating with mates and nursing calfs.

“We’re looking at high levels of mortality, high numbers of hearing loss, enormous amounts of disruptions and potential life functions. It’s not sustainable without better mitigation,” he said.

Hess said the Navy learned “a great deal through its investigation of the Bahamas stranding,” and followed up with “a thorough analysis of the potential environmental effects of our activities.”

And yet, Jasny said, strandings linked to use of Navy sonar continue.