The Navy has agreed in court to drastically limit deployment of its controversial low-frequency sonar system, which environmental groups contend is so loud that it can disorient and kill already endangered whales and other sea creatures.

By agreeing to a permanent injunction against global use of the new sonar, the Navy gave the environmental groups what they called a “groundbreaking” agreement and success. The accord, which limits the Navy to less than 1 percent of the global range that it requested and that was granted initially by federal authorities, was reached last week as part of a lawsuit in federal district court in California.

Environmental groups said they will use their success with the U.S. Navy to begin a worldwide campaign against the high-powered, low-frequency sonar and that a bill was scheduled to be introduced Monday in the European Parliament to limit the sonar use by NATO.

But the groups may not be celebrating for long because military leaders are pushing for legislative changes that would allow the use of such sonar. Navy spokesman Lt. Cmdr. Cappy Surette said Monday that the Navy does not see the agreement as a positive development and that “it will limit the readiness of our sailors and Marines to meet the submarine threats of the new century.”

He said the agreement and permanent injunction also “highlight why legislative change is required to achieve a statutory regime that effectively considers important national interests and national defense.”

The Navy has been a vocal advocate for legislation that would modify the Marine Mammal Protection Act and other environmental laws that military leaders say stand in their way of properly ensuring national security. The bill with the Pentagon’s changes, called the Range and Readiness Preservation Initiative, passed both the House and Senate this year as an amendment to the Defense Department appropriations bill. But it is still being debated in a conference committee because the House and Senate versions had significant differences.

In particular, Surette said, the Navy wants to see the law clarified regarding what constitutes “harassment” of whales, dolphins and porpoises and how many of them can be killed inadvertently without breaking environmental laws. He said that if the House bill becomes law, then the “issues before the California court would be resolved.”

Under the permanent injunction, the Navy will be allowed to use the new sonar – which emits very loud, low-frequency sound that can travel for hundreds of miles – only along the eastern seaboard of Asia, or about 1.5 million square miles. The Navy says the new sonar is essential to detect at long range the new “quiet” submarines being deployed by many navies.

The agreement prohibits the use of the sonar, called Surveillance Towed Array Sensor System-Low Frequency Active, around wildlife-rich Hawaii in particular, although the National Marine Fisheries Service earlier had allowed the Navy to deploy there. The injunction also restricts use of the sonar during seasons when marine mammals are migrating through the approved area and along the coastlines of the approved area, which includes China, Korea, Japan and the Philippines.

Surette said that there is no scientific support to the charge that low-frequency sonar will harm sea creatures and that the Navy spent $10 million to do an environmental impact assessment that found in its favor. But other researchers have concluded that high-powered sonar can and does cause marine mammals to beach themselves and die.

Researchers are still not certain how the loud sonar blasts affect marine mammals. But last week, English and Spanish researchers announced in the journal Nature that they had found gas bubbles in the tissues of some beached whales, indicating they may have risen too quickly to escape the noise and developed decompression sickness or “the bends.” The whales tested had beached in the Canary Islands, just a few hours after active, midfrequency sonar had been used as part of a Spanish-led, international naval maneuver.

The research so far has been on already-deployed midfrequency sonar, but some scientists contend that low-frequency sonar would have the same effect on different species of whales and other sea animals.

“This agreement safeguards both marine life and national security,” said Joel Reynolds, director of the Marine Mammal Protection Project at the Natural Resources Defense Council, the lead plaintiff in the lawsuit against the Navy. “It will prevent the needless injury, harassment and death of countless whales, porpoises and fish, and yet allow the Navy to do what is necessary to defend the country.”

Reynolds said the restrictions will not be in force during times of war or times of officially declared increased threat.

The temporary injunction was ordered by U.S. Magistrate Elizabeth Laporte in August, who struck down the permit issued 15 months ago by the National Marine Fisheries Service. NRDC, the Humane Society International and Jean-Michel Cousteau’s Oceans Future Society brought that lawsuit.

The environmental groups involved said Monday they planned to internationalize the campaign against active sonar in an effort to achieve some global regulation. The International Fund for Animal Welfare, which is based in Europe and claims to have 2 million members worldwide, said Monday that it will actively lobby European governments and the European Union to limit the deployment of the high-powered sonar.

While information about which countries are testing the low-frequency active sonar remains unclear, environmental officials said Monday they believed many nations in Europe and the NATO organization are involved. Reynolds said he did not believe any low-frequency sonar systems have yet been deployed.