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The U.S. Navy is reviewing the impact of its operations on marine mammals after an environmental organization threatened to sue this summer in response to the death of two whales near San Diego.

The Navy’s Pacific military exercises from Southern California to Hawaii fall under a approved in 2018 which gives the military an authorized “incidental take” — a calculation of the number of times the government believes Navy operations could harass, injure or kill marine mammals.��

But critics question the accuracy of its estimates.��

“Throughout the documents, they largely just dismiss the possibility that there will be a ship strike at all,” said Kristin Monsell, oceans program litigation director at the Center for Biological Diversity, a nonprofit that advocates for the protection of endangered species.

Navy officials have insisted they would know if they struck a whale. But the center threatened to sue after an Australian Navy destroyer unknowingly dragged two dead fin whales during a U.S.-led exercise in San Diego over the summer.

The Navy announced in July it would conduct the review.��The Navy’s permit allows up to two fatal encounters with fin whales, but the Endangered Species Act also requires the government to reevaluate its calculations if new information or factors it hadn’t considered come to light.

“I think the destroyer pulling into base with those two fin whales stuck to its hull shows that those assumptions are erroneous and that ship strikes are a much larger threat to these endangered whales than the Navy considered,” Monsell said.

Over the last few decades, the Navy has hired scientists to collect and analyze data on the environmental impact of its operations. The Navy has also spent millions on supporting marine biology and oceanography research at universities and other civilian institutions.��

However, the U.S. Pacific Fleet did not respond to numerous requests for interviews with its environmental team or answer questions about how many documented “incidental takes” it has recorded near Hawaii.

“In the case where you have to write it down on a logbook, that’s only when there’s like actual proof that this thing occurred and it’s unignorable,” said Navy veteran Zoe Garland, who served on both ships and aircraft over her seven-year career. “If there’s an opportunity to leave a logbook blank for something like ‘we hit a whale,’ they’re going to do it. It’s very likely that that’s going to occur.”

Unknown Variables

Joseph Mobley, a professor at the University of Hawaii Manoa who studies marine mammal behavior, has monitored Navy exercises in Hawaii over the years through a program that brings in independent scientists to record impacts on local marine wildlife and provide data to the Navy.

“We’d fly ahead of the destroyer, and if there were whales in the area, we would alert them and then they would try and go around them and so on, but also our task at that time was to assess changes in behavior,” Mobley said.��

Mobley said Navy officials took his findings seriously and used them to guide operations. “We never felt like we were under the gun to try and show everything’s fine,” he said.

But while Mobley’s experiences have been positive, he said he’s not naive about why the military came to scientists like him. “This wasn’t the benevolence of the Navy,” he said. “This was basically the Navy responding to the threat of litigation and so on.”

Among the impacts Mobley watched for most closely was from sonar, as well as from other potentially noisy training.

Mobley said that overall there seems to be little impact from sonar on most local species, with the exceptions of some species of beaked whales. Sonar may frighten them and cause them to quickly ascend, causing a condition similar to the bends.

“You would think after millions of years of evolutionary adaptation they wouldn’t, but I guess, throughout their evolution they didn’t have anything like sonar until recently,” Mobley said. “That causes them disorientation, they wind up beaching themselves and then they die subsequent to being beached, usually.”

But Mobley stressed that most other species around Hawaii don’t react much to sonar or even live-fire training and rarely seemed to be harmed. He said he has seen whales lingering as close as 100 meters to ships near Hawaii.

He believes that mammals in particular have learned to recognize Navy activity around Hawaii and became habituated to it over generations. The exceptions are large training events like RIMPAC which Mobley describes as being “like a rock concert” in their habitat. Mammals tend to stay clear but return after ships have left.

Elsewhere, such as in the Caribbean and Mediterranean seas, there have been a series of beachings and whale deaths tied directly to military training. Along the California coast, mammals have been observed avoiding military vessels using sonar. Mobley said the apparent lack of impacts to wildlife in Hawaii warrants further study. “Hawaii may be something of an anomaly that way,” he said.��

But Mobley said there may be unknown variables. “The caveat of course is that just because we didn’t discern it, because we were humans with eyeballs up there, it doesn’t mean that something didn’t happen,” he said.

Critics of the Navy argue that there are many unknown — and undocumented — factors.

A Crowded Ocean

The U.S. Navy’s operations don’t exist in a vacuum. Other navies also conduct constant operations in the Pacific and have environmental impacts of their own.

The Chinese military has increasingly transformed reefs into military bases and built artificial islands as it seeks to assert control over . Satellite imagery suggests these operations are having a , but scientists haven’t been able to conduct research up close.

Mobley points out that it’s also not just military vessels that can harm. The Pacific Ocean is bustling with commercial, scientific and recreational activity. Whale watchers, fishermen, yachters and merchant vessels constantly move through Hawaii’s waters and have at times collided with wildlife.��

“Here in Hawaii, any boat traveling faster than, say, 15 knots, we would be concerned about ship strikes,” Mobley said.

Federal documented at least 26 whales killed in strikes with vessels of all kinds along the West Coast from 2014 through 2018. Recent studies suggest there may be even more, with some estimating that the actual number could be as much as 20 times higher since most dead whales sink without crews ever knowing.

Even without sonar or weapons firing, the constant movement of ships can also be loud. Recent research suggests that even seagrass is .

Monsell said the U.S. military can take the lead in mitigating those impacts. Among them, the Center for Biological Diversity has requested the Navy slow its ships when traveling through known marine mammal habitats.

Monsell also notes policies that the Navy has abandoned that it could reinstate. “There were previously mitigation areas off Hawaii that are biologically important areas for different species and within those areas there was previously a total ban on sonar but now there’s only seasonal restrictions in place,” Monsell said.

“Those (are) some specific things that we think the Navy can do so that we don’t keep seeing more dead whales in our oceans and on our beaches,” she said.