Coral reefs support immense biodiversity and provide important ecosystem services to many millions of people. Yet reefs are degrading rapidly in response to numerous anthropogenic drivers. In the coming centuries, reefs will run the gauntlet of climate change, and rising temperatures will transform them into new configurations, unlike anything observed previously by humans. Returning reefs to past configurations is no longer an option. Instead, the global challenge is to steer reefs through the Anthropocene era in a way that maintains their biological functions. Successful navigation of this transition will require radical changes in the science, management and governance of coral reefs.

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In an effort to deliver better outcomes for people and the ecosystems they depend on, many governments and civil society groups are engaging natural resource users in collaborative management arrangements (frequently called comanagement). However, there are few empirical studies demonstrating the social and institutional conditions conducive to successful comanagement outcomes, especially in small-scale fisheries. Here, we evaluate 42 comanagement arrangements across five countries and show that: (i) comanagement is largely successful at meeting social and ecological goals; (ii) comanagement tends to benefit wealthier resource users; (iii) resource overexploitation is most strongly influenced by market access and users' dependence on resources; and (iv) institutional characteristics strongly influence livelihood and compliance outcomes, yet have little effect on ecological conditions. common property | governance | human-environment interaction | institutional design principles | common-pool resources

To minimize the impacts of climate change on human wellbeing, governments, development agencies, and civil society organizations have made substantial investments in improving people's capacity to adapt to change. Yet to date, these investments have

Continuing degradation of coral reef ecosystems has generated substantial interest in how management can support reef resilience. Fishing is the primary source of diminished reef function globally, leading to widespread calls for additional marine reserves to recover fish biomass and restore key ecosystem functions. Yet there are no established baselines for determining when these conservation objectives have been met or whether alternative management strategies provide similar ecosystem benefits. Here we establish empirical conservation benchmarks and fish biomass recovery timelines against which coral reefs can be assessed and managed by studying the recovery potential of more than 800 coral reefs along an exploitation gradient. We show that resident reef fish biomass in the absence of fishing (B0) averages ∼1,000 kg ha(-1), and that the vast majority (83%) of fished reefs are missing more than half their expected biomass, with severe consequences for key ecosystem functions such as predation. Given protection from fishing, reef fish biomass has the potential to recover within 35 years on average and less than 60 years when heavily depleted. Notably, alternative fisheries restrictions are largely (64%) successful at maintaining biomass above 50% of B0, sustaining key functions such as herbivory. Our results demonstrate that crucial ecosystem functions can be maintained through a range of fisheries restrictions, allowing coral reef managers to develop recovery plans that meet conservation and livelihood objectives in areas where marine reserves are not socially or politically feasible solutions.

Sustainably managing ecosystems is challenging, especially for complex systems such as coral reefs. This study develops critical reference points for sustainable management by using a large empirical dataset on the coral reefs of the western Indian Ocean to investigate associations between levels of target fish biomass (as an indicator of fishing intensity) and eight metrics of ecosystem state. These eight ecological metrics each exhibited specific thresholds along a continuum of fishable biomass ranging from heavily fished sites to old fisheries closures. Three thresholds lay above and five below a hypothesized window of fishable biomass expected to produce a maximum multispecies sustainable yield (B MMSY ). Evaluating three management systems in nine countries, we found that unregulated fisheries often operate below the B MMSY , whereas fisheries closures and, less frequently, gear-restricted fisheries were within or above this window. These findings provide tangible management targets for multispecies coral reef fisheries and highlight key tradeoffs required to achieve different fisheries and conservation goals.human-environment interactions | sustainable fisheries | marine protected areas | resilience | social-ecological systems C oral reefs have proven difficult to manage sustainably, in part because the multispecies nature of reef fisheries, the complexity of trophic interactions, and the times scales on which processes manifest may allow coral reefs to appear healthy long after serious degradation has occurred (1, 2). This also means that signs of degradation may not be readily apparent in the information that many managers use to evaluate the condition of reef systems [metrics such as catch data or coral cover (2)]. In addition, most reefs are located in developing countries (3) where food security concerns often take priority over conservation. In the absence of reference points that signal when further exploitation may have serious consequences for reef ecosystems, managers are often unlikely to make the socially and politically difficult decisions to restrict fishing activities. A question of critical relevance to scientists, managers, and resource users alike is whether meaningful limits or reference points can provide effective warning of conditions beyond which coral reef social-ecological systems incur a risk of serious degradation and lost value (4, 5).Here we examine where major changes in coral reef systems occur along a gradient of fishable biomass, a readily measured and managed variable, and explore how this can be used to define key reference points that can help inform management decisions (4, 6). We compiled information from more than 300 surveys of shallow coral reefs from nine countries across the Indian Ocean (Table S1 ). Survey sites spanned some 35°of latitude and 52°of longitude and were evenly distributed among unregulated, restricted, and fisheries closure management areas (details in SI Methods). We used a suite of four statistical models (null, linear, switch-point, and piecewis...

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