Modelling coral reef biodiversity for prioritizing marine protected area in Madagascar and adjacent islands

Purpose To determine the distribution of biodiversity in coral reefs of Madagascar, Comoros, and Mayotte. Methods A Gradient Boosting Model (GBM) evaluating seventy environmental spatial databases predicted reef biodiversity field data to create spatial predictions in 2854 6-km ² mapped reef cells in 2020 and 2050. Predicted biodiversity were compared to past provincial protected area prioritization activities and the current listing of marine national parks (MNP), Locally Managed Marine Areas (LMMAs), and the World Protected Area Database (WDPA). Results Twenty-one national high biodiversity priority cells were selected for Madagascar, 3 for Mayotte, and 8 for Comoros. Sixteen of the 32 selected high biodiversity locations were contained in 44 of the 102 possible listed WDPA protected areas. The east and coastal reefs south of Antongil Bay and offshore coral reefs islands were notably excluded from national but not LMMA designations. Madagascar’s west coast was better represented than the east coast in WDPA locations. Based on surface temperate predictions, coral cover declined in 55% and gained in 7%, while numbers of taxa declined in 72% but gained in 14% of the grid cells between 2020 and 2050. Conclusions Spatial cells with minor climate-induced changes or gains in coral reef cover and diversity attributes were broadly scattered among governance authorities. However, most locations with little climate change effects were in southwest Madagascar where overfishing is likely to undermine their climate refugia potential.