2024 Mesoamerican Reef Health Report Card Records Improvement Despite Growing Challenges

The 2024 Mesoamerican Reef Health Report Card evaluated 286 sites, noting an improvement in the Reef Health Index (RHI) from 2.3 (2021) to 2.5 (2023), out of a possible 5. However, 62% of sites remain in poor or critical condition, with only 10% rated good or very good. Regionally, coral cover and herbivorous fish biomass ranked ‘fair,’ while fleshy macroalgae and commercial fish biomass ranked ‘poor,’. Herbivorous fish biomass increased from 1,843g/100m² to 2,419g/100m² (2021-23), with notable gains in Belize and Guatemala. Commercial fish biomass remained stable except in Belize, which saw an increase from 330g/100m² to 791g/100m² (2021-2023). Coral cover decreased from 19% to 17%, primarily due to disease and bleaching. All reefs were exposed to severe heat stress, with approximately 40% of corals experiencing severe bleaching during 2023. However, most coral mortality occurred after the monitoring  season, as in the iconic Banco Cordelia, Roatan, Honduras which went from 46% live coral in September 2023 to 5% in February 2024.  

Higher grouper and snapper biomass is found within the Fully Protected Zones (FPZs), where all types of fishing is prohibited.  FPZs cover only 3% of the MAR’s territorial seas and 11% of its coral reefs. Thus, there is great potential to improve reef health by expanding the area in full protection within the much larger Marine Protected Areas (MPA) areas already designated. There are >50 MPAs covering 57% of the territorial seas within the MAR. Well-managed and enforced MPAs are crucial for replenishing fish populations, particularly those with additional regulations like parrotfish and surgeonfish, which are protected in most of the MAR;  and Nassau groupers, which are the only fin fish species with size limits and a closed season across the MAR. The Nassau grouper was the only species of grouper to have a relatively balanced size distribution with 44% of the fish surveyed meeting the minimum reproductive size, although total numbers are still very low.  Integrating FPZs in ecologically critical areas, including Fish Spawning Aggregation sites and areas believed to be less prone to heat stress events, is vital for the maintenance of ecological structure and function and the large ecosystem scale of the Mesoamerican Reef. 

Increasing the area in full protection to 20% has been a recommendation since our first Report Card was issued in 2008. Increases have been small and incremental compared to the pace and scale of the additional stressors.  Improving sewage treatment and land use management in watersheds and coastal areas has also been a recurring recommendation for decades, with many versions of plans produced but few examples of effective implementation of these plans. Finally, without urgent and almost impossible reductions in greenhouse gasses, the escalating heat stress will soon overwhelm the adaptive capacity of coral reefs that continue to be stressed by anthropogenic stressors identified over thirty years ago. Our two decades of collaborative science-based monitoring and reporting has described way to assist coral reef survival, but it cannot implement the needed political actions, which may require a different novel approach.