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Ecosystems worldwide are under increasing threat. We applied a standardized method for assessing the risk of ecosystem collapse, the International Union for Conservation of Nature (IUCN) Red List of Ecosystems, to coral reefs in the Western Indian Ocean (WIO), covering 11,919 km2 of reef (~5% of the global total). Our approach combined indicators of change in historic ecosystem extent, ecosystem functioning (hard corals, fleshy algae, herbivores and piscivores) and projected sea temperature warming. We show that WIO coral reefs are vulnerable to collapse at the regional level, while in 11 nested ecoregions they range from critically endangered (islands, driven by future warming) to vulnerable (continental coast and northern Seychelles, driven principally by fishing pressure). Responses to avoid coral reef collapse must include ecosystem-based management of reefs and adjacent systems combined with mitigating and adapting to climate change. Our approach can be replicated across coral reefs globally to help countries and other actors meet conservation and sustainability targets set under multiple global conventions—including the Convention on Biological Diversity’s post-2020 global biodiversity framework and the United Nations’ Sustainable Development Goals.

Protected and Conserved Areas (PCAs) are key ecosystem management tools for conserving biodiversity and sustaining ecosystem services and social co-benefits. As countries converge on a 30% target for protection of land and sea under the post-2020 framework of the United Nations Convention on Biological Diversity, a critical question emerging is, “which 30%?”. One approach to an answer is risk-based: we should protect the 30% that returns the greatest reductions in risks of species extinction and ecosystem collapse. IUCN Red List protocols provide practical methods for assessing these risks. All species, including humans, depend on the integrity of ecosystems for their well-being and survival. Africa is strategically important for ecosystem management due to convergence of high ecosystem diversity, intense pressures and high levels of human dependency on nature. We reviewed the outcomes of a symposium at the inaugural African Protected Areas Congress convened to discuss applications of the IUCN Red List of Ecosystems to the design and management of PCAs. We found significant recent progress in red listing, with c. 1000 ecosystem types assessed across 21 countries. While these span a diversity of environments across the continent, the greatest thematic gaps are in freshwater, marine and subterranean realms and large geographic gaps exist in north Africa and parts of west and east Africa. The projects are implemented by a diverse community of government agencies, NGOs and researchers. Already, they are having impact on policy and management, informing extensions to formal Protected Area networks, supporting decision making for sustainable development and informing ecosystem conservation and threat abatement, both within boundaries of PCAs and in surrounding landscapes and seascapes. We recommend further integration of risk assessments into environmental policy and enhanced investment in ecosystem red listing to fill current gaps.

Ocean warming is increasing the incidence, scale, and severity of global-scale coral bleaching and mortality, culminating in the third global coral bleaching event that occurred during record marine heatwaves of 2014-2017. While local effects of these events have been widely reported, the global implications remain unknown. Analysis of 15,066 reef surveys during 2014-2017 revealed that 80% of surveyed reefs experienced significant coral bleaching and 35% experienced significant coral mortality. The global extent of significant coral bleaching and mortality was assessed by extrapolating results from reef surveys using comprehensive remote-sensing data of regional heat stress. This model predicted that 51% of the world’s coral reefs suffered significant bleaching and 15% significant mortality, surpassing damage from any prior global bleaching event. These observations demonstrate that global warming’s widespread damage to coral reefs is accelerating and underscores the threat anthropogenic climate change poses for the irreversible transformation of these essential ecosystems.

Djiboutian coral reefs are poorly studied, but are of critical importance to tourism and artisanal fishing in this small developing nation. In 2014 and 2016 we carried out the most comprehensive survey of Djiboutian reefs to date, and present data on their ecology, health and estimate their vulnerability to future coral bleaching and anthropogenic impacts. Reef type varied from complex reef formations exposed to wind and waves along the Gulf of Aden, to narrow fringing reefs adjacent to the deep sheltered waters of the Gulf of Tadjoura. Evidence suggests that in the past 35 years the reefs have not previously experienced severe coral bleaching or significant human impacts, with many reefs having healthy and diverse coral and fish populations. Mean coral cover was high (52%) and fish assemblages were dominated by fishery target species and herbivores. However, rising sea surface temperatures (SSTs) and rapid recent coastal development activities in Djibouti are likely future threats to these relatively untouched reefs.

This erratum has been initiated as authors first and last names appeared inverse in the original article and should be correctly read as.