Climate Change Risk Scenarios for Echinometra lucunter (Linnaeus, 1758) in the Colombian Caribbean

Echinometra lucunter (Linnaeus, 1758) is a sea urchin widely distributed throughout the Caribbean, recognised for its pivotal ecological role as a bioindica-tor. Its niche is characterised by herbivory within coral reef frameworks and shal-low rocky substrates, where it significantly contributes to nutrient cycling and net primary productivity across Caribbean marine ecosystems. However, anthropo-genic climate change poses a substantial threat to its populations, specifically through perturbations in marine hydrochemistry. This study aims to estimate and analyse the habitat suitability of E. lucunter in the Southwestern Caribbean under current conditions and future climate risk scenarios. To achieve this, we employed ecological niche modelling (ENM) using an ensem-ble forecasting approach that integrates multiple algorithms, including Maximum Entropy (MaxEnt), Generalized Linear Models (GLM), and Random Forest (RF). Models were calibrated using physical and chemical oceanographic variables and projected onto two contrasting climate pathways (SSP1-1.9 and SSP5-8.5) for the 2040–2050 horizon. Our results indicate that while the contemporary distribution of the species is strongly dictated by physiographic factors such as bathymetry and coastal proximity biogeochemical variables, including pH fluctuations, sea surface temperature (SST), and chlorophyll-a net productivity, are the primary drivers of habitat suitability shifts. Both future scenarios project a marked niche contraction, characterized by severe loss of core habitat and a high risk of local extirpation. Con-versely, specific insular and coastal regions in Colombia may serve as climate re-fugia, suggesting a potential buffering effect against regional declines. In conclu-sion, E. lucunter emerges as a species highly vulnerable to climate-driven stress-ors, underscoring the urgent requirement for spatially explicit conservation strate-gies within the Caribbean basin.