On coastal reefs (0-50 m depth), perhaps more than anywhere in the world, natural and human systems share a history of strong dependence that must be taken into account to maintain, on one side, the long-term human development and well-being, and, on the other side, biodiversity. This biodiversity translates directly into services. Reef fishes support the nutritional and economic needs of people in many poor countries while hosting the major part of marine life on Earth (25%). However world's reefs are severely over-fished or have degraded habitats. Avoiding or escaping this negative spiral and identifying the most vulnerable reef social-ecological systems on Earth are among the major issues that scientists and managers are facing today. The project aims to move beyond the typical over-simplified ‘human impacts’ storyline and focus on uncovering new solutions based on a prospective and integrated modelling approach of reef social-ecological systems at the global scale with three objectives: 1.Quantifying five key services provided by reef fishes: (i) biomass production providing livelihoods, (ii) nutrient cycling that affects productivity, (iii) regulation of the carbon cycle that affects CO2 concentration, (iv) cultural value that sustains well-being tourism activities and (v) nutritional value insuring food security. 2.Determine the conditions (socioeconomic and environmental) under which these ecosystem services are currently maintained or threatened. Based on a global database of fish surveys over more than 5,000 reefs that encompass wide gradients of environments, human influences (fishing impact), and habitats, we will estimate the boundaries or thresholds beyond which these ecosystem services may collapse. 3.Predict the potential futures of these services and social-ecological systems under various global change scenarios. Using multiple integrated scenarios (human demography, economic development and climate change) and predictive models we will simulate the dynamics of shallow reef ecosystems and their ability to deliver services during the next century.