The MarCons Cost Action will consolidate a network of scientists and stakeholders who are involved in marine conservation in European and contiguous seas. By advancing the science of integrated conservation planning, promoting regional coordination and transboundary conservation, proposing specific conservation actions, accounting for climatic change and biological invasions, and providing guidance for assessing governance issues to make marine spatially managed areas more effective, this Cost Action aims to bridge the gap between conservation science and policy makers and substantially contribute to the challenge of halting biodiversity loss in the European Seas by 2020.