Fig. 4: Present and future projections of genomic vulnerability across global reefs.

Global map of coral reefs colored by expected frequency of heat-adaptive genotypes based on heat stress before 2020 (0–50%: red, 50–70%: yellow, 70–100% green). The intensity of colors represents the intensity of heat stress [maximal Degree Heating Week (DHW_max)] during 2020–2024 (low: <4 °C-week, significant: ≥4 and <8 °C-week, severe: ≥8 °C-week). In grey, reefs are exposed to heat stress levels beyond the predictable range of the environmental genomics model. B Global map of expected frequency of heat-adaptive genotypes based on heat stress before 2035. The intensity of colors represents the intensity of forecasted heat stress during 2036-2040. C Year-by-year projected proportions of reefs exposed to severe heatwaves (top graph), of reefs with an expected frequency of heat-adaptive genotypes above 70% (middle graph) and of reefs under genomic vulnerability (i.e., reefs exposed to severe heatwaves and having an expected frequency of heat-adaptive genotypes below 70%; bottom graph). Full lines represent projections from past heat stress data, and dotted lines from forecasted heat stress under a moderate climate change scenario (SSP2-4.5)⁵². Shaded areas in the background display the range of projections across ten oceanic regions. D Estimated mutations-area relationship (MAR) of the Acropora populations (black line, shaded area as interval of confidence). Points represent the mean genetic diversity loss per area loss (bars represent the 95% confidence interval), as observed in stochastic simulations of extinction across all datasets (N = 58). Solid arrows indicate the proportion of global reef area at risk of extinction according to heatwave exposure (blue) and genomic vulnerability (purple)–––based on 2020-2024 projections. For these potential losses of reef area, dashed lines indicate the corresponding genetic loss. E Mean proportion of reefs (N = 45,577) with expected frequency of heat-adaptive genotype above 70% inside (black) and outside (grey) marine protected areas (MPA), globally and by oceanic region (genotype frequencies predicted in 2024). Background map was produced using the Global Relief Model from NOAA (ETOPO 2022⁸²) and the Global Distribution Map of Coral Reefs from the UNEP World Conservation Monitoring Center⁸³.