IUCN Red List of Ecosystems: Coral Reefs of the Eastern Tropical Pacific

Andrea Arriaga-Madrigal, Manuel Olán-González, Juan P. Quimbayo, Juan José Alvarado, Imelda Amador, Arturo Ayala-Bocos, Luis Calderón-Aguilera, José Julio Casas-Maldonado, Amílcar Leví Cupul-Magaña, Priscilla Martinez, Ollin T. González-Cuellar, Rebeca Granja-Fernandez, Inti Keith, Andrés López-Pérez, Nicolas Moity, Damien Olivier, Georgina Ramírez-Ortiz, Héctor Reyes-Bonilla, Fernando Rivera, Jenny Carolina Rodríguez-Villalobos, Fabián A. Rodríguez-Zaragoza, Johanna Segovia-Prado, Omar Valencia-Méndez, Franz Smith, Mishal Gudka, Sonia Bejarano, Fernando A. Zapata

Coral reefs in the Eastern Tropical Pacific (ETP), covering 140 km² (0.04% of the total global coral reef extent), are under increasing climate and anthropogenic threats. Coral reef development and species distribution in the ETP are conditioned by the characteristic isolation of the region and its strong environmental variability, including El Niño-Southern Oscillation (ENSO) events and upwelling. Focusing on coral reefs, marginal reefs, and their degraded/collapsed counterparts, located in Mexico, El Salvador, Nicaragua, Costa Rica, Panama, Colombia, and Ecuador, and encompassing five coastal and five oceanic ecoregions, we applied a standardized method to assess the risk of ecosystem collapse based on four criteria (i.e., decline in distribution, restricted geographic distribution, environmental degradation, and disruption of biotic processes and interactions). The ETP is characterized by a high overall risk of coral reef ecosystem collapse, with nine of the ten ecoregions classified as Critically Endangered and one ecoregion Collapsed. Across ecoregions, collapse risk was primarily associated with severe environmental degradation, particularly increasing thermal stress, although the relative contribution of other factors varied geographically. In three Critically Endangered ecoregions, severe environmental degradation was compounded by additional vulnerabilities, including reduced geographic distribution and disruption of biotic processes and interactions in Nicoya, reduced geographic distribution in the Eastern Galápagos Islands, and inherently restricted geographic distribution in Clipperton Atoll. The widespread high-risk status across both continental and oceanic ecoregions indicates that reef decline is not driven by a single pressure, but rather by the convergence of naturally marginal environmental conditions with accelerating climate and local anthropogenic stressors. These include thermal stress and coral bleaching, as well as land-based pollution, sediment and nutrient inputs, wastewater discharge, coastal development, and unsustainable fishing. The reef extent assessment conducted here represents the best available regional estimate and a standardized baseline for evaluating reef collapse risk. These results highlight the urgent need to safeguard the remaining coral-dominated reefs, persistent coral refugia, and herbivore and piscivore assemblages through coordinated regional management. Priority actions include reducing land-based pressures along continental margins, strengthening fisheries management and enforcement, maintaining ecological connectivity among reefs, as well as strengthening reef monitoring programmes regionally. Integrating these measures with transboundary governance, effective management of Marine Protected Areas, restoration actions, ecosystem-based management, direct conservation of resilient reefs, and climate-adaptation strategies will be essential to prevent further ecosystem collapse.