The welfare costs that this imposes on society are high and pressures from human activities are projected to grow. Though no single definition exists, MPAs are generally described as any defined area within or adjacent to the marine environment which has been reserved by legislation or other effective means so that its marine and/or coastal biodiversity enjoys a higher level of protection than its surroundings. In addition to protecting habitats, and buffering against storms and erosion, MPAs can help ensure the provision of multiple other ecosystem services that are fundamental for human well-being, including for fisheries, tourism, recreation and carbon storage.