Forty-one environmental groups banded together yesterday to criticize an effort by the U.S. Navy to exempt two military bases in California from provisions of the Endangered Species Act. Navy officials say they need the exemptions for national security reasons and claim they will implement their own species-protection efforts. In a formal letter to the U.S. Fish and Wildlife Service, which will decide whether to grant the Navy’s request, the coalition of enviro groups argues that making the exemptions “would set a terrible precedent for similar unjustified exemptions … across the country.” The enviros say the military’s activities are already encroaching on habitat for the endangered gnatcatcher songbird and the fairy shrimp.