Navy training using sonar and explosives around Hawaii presents risks to thousands of whales and dolphins every year from temporary hearing loss, but the impacts are unlikely to lead to any long-term consequences for marine mammal populations, the service said in a new report.

The final environmental impact statement released Friday evaluates potential effects in what’s known as the Hawaii-Southern California Training and Testing Study Area.

“Individual (marine) animals would typically only experience a small number of behavioral responses or temporary hearing threshold shifts per year due to exposure to acoustic stressors,” the Navy said, adding that mitigation efforts will continue to be practiced to minimize harm.

But David Henkin, an attorney for Earthjustice in Honolulu, said the “extraordinarily high numbers of whales, dolphins and other marine mammals the Navy admits would be harassed, injured or killed by its training and testing activities is alarming.”

“While the Navy has proposed some limited measures to curb sonar and explosives use around Hawaii island and Maui County, it has failed completely to protect vulnerable marine mammal populations around Kauai and Oahu,” Henkin said.

He added, “We are carefully reviewing the final environmental impact statement to assess whether the Navy has complied with its legal duty to do everything it reasonably can to protect marine mammals — including several critically endangered species — from harm.”

Henkin said it’s not a question of whether the Navy will be able to conduct necessary training, but rather how the Navy carries out its mission to protect the nation — including “vulnerable and irreplaceable biological treasures.”

The Navy environmental review is necessary for the issuance of federal permits under the Marine Mammal Protection Act and the Endangered Species Act. A similar analysis was conducted for training and testing activities from 2013 to 2018.

The study area consists of at-sea regions off the coasts of Hawaii and Southern California; areas on the high seas between the Navy’s Hawaii and Southern California range complexes; the Temporary Operating Area north and west of the Hawaii Range Complex; and select Navy pierside and harbor locations.

Federal regulations provide for a 30-day waiting period after the final environmental impact statement is published before the Navy may take final action. The document is available at HSTTEIS.com.

The Navy said it needs the sonar and explosive training to ensure that it meets its mission to train combat-ready naval forces capable of winning wars, deterring aggression and maintaining freedom of the seas.

The planned activities are “generally consistent” with those previously analyzed, the service said.

The review “supports the Navy’s increased focus on live training to meet evolving surface warfare challenges,” the Navy said. “This results in a proposed increase in levels of air-to-surface warfare activities and an increased reliance on the use of non-explosive and explosive rockets, missiles, and bombs.”

Reporting has been updated to reflect new active sonar sources, such as high-frequency imaging sonars and broadband sound sources proposed for testing and experimentation, the Navy said. A net increase in testing systems that use sonar is projected.

The Navy said it will implement mitigation wherever training occurs involving acoustic, explosive and physical disturbance. That generally involves the use of trained lookouts for species including marine mammals and sea turtles and requirements for the watch station to implement mitigation.

Among other species and effects, 4,296 pygmy sperm whales and 2,703 minke whales are expected to experience some temporary hearing loss per year in the Hawaii area. A total of 44 Hawaiian monk seals would experience some effect annually. That also applies to 910 Fraser’s dolphins.

Training will include everything from airplanes dropping bombs on surface targets and helicopter, ship and submarine anti-submarine training, to high-energy lasers and at-sea sonic booms.

The activity “could contribute incremental stressors to (marine animals), which would both further compound effects on a given individual already experiencing stress and, in turn, have the potential to further stress populations, some of which may already be in significant decline or in the midst of stabilization and recovery,” the Navy said. “However, with the implementation of standard operating procedures reducing the likelihood of overlap in time and space with other stressors, and the implementation of mitigation measures reducing the likelihood of impacts, the incremental stressors … are not anticipated to be significant.”