Corais brasileiros e mudanças climáticas globais: projeções futuras e hotspots de vulnerabilidade

Abstract

Global climate change is a major threat to coral reefs around the world, increasing the annual frequency and severity of bleaching events, causing loss of living coral cover, complexity and diversity of coral reefs. Repeated and intense bleaching events can reduce the thermal tolerance and recovery capacity of coral species, so corals will likely depend on refuge areas that will become more suitable as ocean warms (e.g. extratropical reefs), that are less impacted by increasing temperatures (e.g. deeper reefs) and where local human impacts are minimized, potentially enabling acclimation and adaptation. Therefore, identifying potential refugia and the most vulnerable areas to coral bleaching is critical to minimize local impacts and enhance coral´s ability to cope with climate change. We used Bayesian Hierarchical Spatial Model to project coral occurrence, cover and bleaching probabilities along the Brazilian coast that harbors the largest and richest marginal reefs in Southwestern Atlantic, and predicted how these probabilities are likely to change by 2050 and 2100, based on the RCP8.5 scenario forecasted by the Intergovernmental Panel on Climate Change (IPCC). By overlapping these predictive models, we identified the most vulnerable areas to coral bleaching (hotspots) under current and future scenarios. We identified higher coral occurrence and cover probabilities in tropical than subtropical regions of the Southwestern Atlantic under current conditions. By 2050 and 2100, the projections indicate an increase in coral occurrence and cover probabilities toward extratropical and deeper offshore reefs, which could act as refugia. However, the role of these areas as refugia also depend on the bleaching probability, which tend to increase in future projections, and on the synergic effects of other anthropogenic impacts. The vulnerability hotspots were concentrated around the Abrolhos Bank, the largest and richest coral reef area in South Atlantic, both in current and future projections. This area comprises a network of marine protected areas that should be reinforced to mitigate local impacts and enhance the ability of corals to cope with increasing temperatures. The combination of these modelling approaches can be a powerful tool to inform conservation actions to face global climate changes accounting for future range expansion and increase in bleaching probabilities.