Evaluation of active sonar risk assessment tools

The EU Marine Strategy Framework Directive (2008/56/EU) stipulates that in 2020, a good environmental status should prevail in European waters. The Directive specifies eleven descriptors that describe what is meant by a good environmental status. The 11th descriptor states that underwater noise must not be at levels high enough to negatively affect the marine environment. The Marine Directive does not strictly apply to peacetime military operations, but European Navies still need to address it. Sound and noise can affect marine life in several different ways, ranging from direct physical impact to behavioural distance and masking of calls. The possible impact of naval activities and in particular active sonar on marine mammals has received significant attention after several mass strandings of whales in conjunction with active sonar exercises. Several countries have strived to reduce the risks to marine life from active sonar. The work has focused on marine mammals because they have displayed the largest negative effects and have better hearing than fish at typical sonar frequencies. In Swedish waters there are four resident species of marine mammals: the harbour porpoise and three seals, the gray, harbour, and ringed seals. The underlying purpose of this report is to discuss how best to provide the Swedish Navy with an active sonar risk assessment tool. Our assessment is that a land-based system managed by expert operators would be appropriate since a broad competence in acoustics and marine biology is needed for a full understanding of the issue and interpretation of risk assessment results. This report presents an evaluation of two risk assessment tools for possible future use by the Royal Swedish Navy (RSwN). ERMC (BAE Systems, UK) is a robust product developed for operational use on board Royal Navy platforms. SAKAMATA (TNO, the Netherlands) has a simpler user interface and should appeal to an expert user, but is less robust than ERMC and should be seen as a tool under development. However, both ERMC and SAKAMATA could be suitable for use by RSwN within a timeframe of a few years. This report also identifies other alternatives of supplying RSwN with a risk assessment tool. A lot of information is required in order to be able to perform a correct risk assessment, and a risk assessment tool is ultimately limited by the quality of the databases that the assessment is based on. An alternative to the explicit risk assessment of ERMC and SAKAMATA is to present maps of biological data and let the user decide where and when it is most appropriate to perform an active sonar exercise. We present two GIS tools that display geographical information of interest in a risk assessment: SONATE (FFI, Norway) and Maringeografisk Biologikalender (RSwN, Sweden). These are good alternatives to risk assessment tools when a reliable risk assessment cannot be performed, and can otherwise serve as a complement to a risk assessment tool.