From AEI’s lay summaries of key science and policy:

A comprehensive report on Mediterranean shipping from the International Union for the Conservation of Nature and Natural Resources includes a long section in the early pages on noise impacts. Due to the concentration of shipping in the Mediterranean, ambient noise is 40dB higher than in relatively shipping-free regions such as the Sea of Cortez. Among the recommendations are that “Much effort should be devoted to developing a legal framework within which underwater noise is recognized and regulated as a threat,” and the advocacy of MPAs that are designed to provide acoustic protection to critical and productive habitats, where “noise levels should not be allowed to exceed ambient by more than a given value, including noise from sources located outside the MPA.” In addition, the report stresses the importance of moving rapidly to develop regional hydrophone networks with which to monitor noise and develop current “noise budgets,” as well as the need for expanded research using new non-invasive methods to examine hearing sensitivity and changes due to noise exposure in wild animals, and analysis of stress hormones in response to noise. The authors of the report forge important new ground as they summarize: “In addition to defining which impacts should be avoided or mitigated, we also need to draw up a model of ‘acoustic comfort’ that we should guarantee to animals, at least over sufficiently extensive protected areas. This is a novel concept. It means we should define the (near to) zero-impact noise level that a habitat should have for each type of marine life.”

Ameer Abdulla, Olof London (editors). 2008. Maritime traffic effects on biodiversity in the Mediterranean Sea: Review of impacts, priority areas and mitigation measures. Malaga, Spain: IUCN Centre for Mediterranean Cooperation. 184 pp. [DOWNLOAD(pdf)] [WEBSITE]