If corals go extinct, half the world's tropical fish may follow

Statistical models show that coral extinctions due to reef bleaching will impact far more species than expected and may reduce global reef fish richness by more than 40 per cent

GBIF-mediated data resources used : Species occurrences of 7,408 tropical marine fish
Caesio caerulaurea
School of Caesio caerulaurea Lacepède, 1801 observed at Hastings Reef, Australia by imogenisunderwater (CC BY-NC 4.0)

Coral reefs contribute food and structural complexity for habitats of fish and other reef organisms. While many reef fish may survive increasing ocean temperature, corals are more sensitive, and effects of extinctions caused by bleaching may extend far beyond the species that strictly depend on corals.

In this study, researchers mapped the global distribution of coral and tropical fish richness using data from GBIF, OBIS and IUCN. They then estimated fish richness dependency on corals using limited natural history information and a statistical model of indirect environmental effects of coral richness on fishes.

Simulating a world without corals, the model predicted that 41 per cent of tropical reef fish species depend on corals and would be lost as well. For a more comprehensive view of the effects of coral loss on fish communities, the authors also considered phylogenetic and functional diversity, for which the model predicted a decline of 32 and 23 per cent, respectively.

While total coral reef extinction may sound pessimistic, climate-based projections predict that 100 per cent of the world's coral reefs will have been exposed to at least one bleaching event by the year 2060 in the most severe carbon emissions scenario.

Strona G, Lafferty KD, Fattorini S, Beck PSA, Guilhaumon F, Arrigoni R, Montano S, Seveso D, Galli P, Planes S and Parravicini V (2021) Global tropical reef fish richness could decline by around half if corals are lost. Proceedings of the Royal Society B: Biological Sciences. The Royal Society 288(1953): 20210274. Available at: https://doi.org/10.1098/rspb.2021.0274