Safe use of military active sonar – national guidelines and Swedish law

The effect of active sonars on marine life has received significant attention in international media and scientific publications. There have been several mass strandings of marine mammals where military active sonars are believed to be the cause (Hildebrand 2004 and Parson et al 2008). However, none of these have occurred in Sweden. Three seal species, namely the grey, harbour and ringed seals, and one cetacean species, the harbour porpoise, inhabit Swedish waters. They face several different forms of threats, including chemical pollutions, bycatch in fishing, diseases and also negative effects from loud noise. Loud noise may harm animals physically but may also induce behavioural reactions that in turn may result in secondary physical injuries. Harbour porpoises in the Baltic Sea may suffer significant behavioural disturbance at up to 20 km from a Swedish Navy VDS (Variable Depth Sonar) active sonar transmitting at full power at a frequency of 25 kHz. They may suffer temporary hearing damage at ranges up to 7 km (Andersson and Johansson 2013). This report presents an overview of Swedish and international laws of relevance to the use of active sonar as well as operational guidelines for active sonar that have been adopted in e.g. France, Norway, Italy, Great Britain and the United States. Marine mammals in Swedish waters are mentioned in lists of species that need protection e.g. the Swedish red list and international red lists as well as national laws like jaktlagen, miljöbalken and artskyddsförordningen. There are designated seal protection areas and two Natura 2000 areas where harbour porpoises are listed. The EU Marine Strategy Framework Directive (2008/56/EU) stipulates that in 2020, European waters shall display a good environmental status. The Directive targets different threats to the marine environment, including underwater noise. Havsmiljöförordningen (2010:1341) implements the Marine Strategy Framework Directive in Swedish Law, and applies to military operations. Miljöbalken (1998:808) regulates all civilian and military activities that may have an effect on the environment. This includes the Swedish Navy's active sonar systems. It requests the Navy to e.g. gather knowledge and implement appropriate protective measures. Moreover, Sweden has ratified several resolutions and conventions that cover the environmental impact of underwater noise. This report suggests scientifically appropriate mitigation measures and practical guidelines for responsible use of active sonar by the Swedish Navy. Examples are inventory of marine mammals at sites proposed for sonar use, implementation of safety zones using visual and acoustic observation, guidelines that specify what is to happen if a marine mammal enters such a safety zone, and documentation of sonar activities, marine mammal observations and possible incidents. Several knowledge gaps must be addressed in order to make the guidelines relevant and effective. This report may form the basis of an effort to draw up and implement operational guidelines for environmentally responsible use of active sonar in the Swedish Navy. Such an effort should be conducted in close collaboration between scientific expertise and all affected branches of the Swedish Armed Forces.