Restoration of marine ecosystems: understanding possible futures for optimal outcomes

Accelerating declines in the extent, quality and functioning of the world's marine ecosystems have generated an upsurge in focus on practical solutions, with ecosystem restoration becoming an increasingly attractive mitigation strategy for systems as diverse as coral reefs, mangroves and tidal flats. While restoration is popular because it promises positive outcomes and a return to something approaching unimpacted condition and functioning, it involves substantial public and private investment, both for the initial restoration activity and for on-going maintenance of the restored asset. This investment often affords one big chance to get things right before irretrievable damage is done. As a result, precise, well considered and accountable decision-making is needed to determine the specific focus for restoration, the scale of restoration, the location for deploying restoration activities, and indeed whether or not restoration is necessary or even possible. We explore the environmental/ecological considerations and constraints governing optimal decisions about the nature, location and prioritisation of restoration activities in marine ecosystems, and in particular the constraints on achieving understanding of possible futures and the likelihood of achieving them. We conclude that action must be informed by a context-specific understanding of the historical situation, the current situation, the constraints on change, the range of potential outcome scenarios, and the potential futures envisioned