Biodiversity enhances reef fish biomass and resistance to climate change

Abstract

Fishes are the most diverse group of vertebrates, play key functional roles in aquatic ecosystems, and provide protein for a billion people, especially in the developing world. Those functions are compromised by mounting pressures on marine biodiversity and ecosystems. Because of its economic and food value, fish biomass production provides an unusually direct link from biodiversity to critical ecosystem services. We used the Reef Life Survey's global database of 4,556 standardized fish surveys to test the importance of biodiversity to fish production relative to 25 environmental drivers. Temperature, biodiversity, and human influence together explained 47% of the global variation in reef fish biomass among sites. Fish species richness and functional diversity were among the strongest predictors of fish biomass, particularly for the large-bodied species and carnivores preferred by fishers, and these biodiversity effects were robust to potentially confounding influences of sample abundance, scale, and environmental correlations. Warmer temperatures increased biomass directly, presumably by raising metabolism, and indirectly by increasing diversity, whereas temperature variability reduced biomass. Importantly, diversity and climate interact, with biomass of diverse communities less affected by rising and variable temperatures than species-poor communities. Biodiversity thus buffers global fish biomass from climate change, and conservation of marine biodiversity can stabilize fish production in a changing ocean.

Keywords: fisheries; functional diversity; global change; macroecology; structural equation model.

Fig. 1.

(A) Path diagram of factors influencing global reef fish biomass. Black and red paths represent positive and negative influences, respectively. Path thickness is proportional to the standardized regression coefficient (SI Appendix, Table S1). Paths of β < 0.05 are not shown. Gray box surrounds abiotic variables (and chl a), for which paths have been omitted for clarity and are shown in SI Appendix, Fig. S1. ^†Log₁₀-transformed. FD, functional diversity; T, sea-surface temperature. (B) Summed direct and indirect effects of temperature, mineral nutrients, biodiversity, and human population density.

Fig. 2.

Global estimates of the effects of biodiversity and environmental drivers on reef fish community biomass. (A) Log biomass as a function of log estimated richness (corrected for sample coverage) (52). (B) Same as A, but using ecoregion means. (C and D) Effect sizes (standardized partial regression coefficients) of 11 predictors of (log) reef fish biomass from the global hierarchical model among (C) sites and (D) ecoregions. (E and F) Log biomass as a function of mean annual temperature at low- and high-richness sites (relative to median richness), respectively. (G and H) Log biomass as a function of annual temperature range at low- and high-richness sites, respectively. S, estimated richness. Blue and green symbols represent tropical and temperate sites, respectively.

Fig. 3.

Relative influence of biodiversity and environmental factors on log biomass of reef fishes by trophic level (A–D) and latitudinal zone (E and F). Effect sizes are standardized partial regression coefficients (β) from hierarchical linear models estimated separately for each case. Carnivores, top carnivores; invertivores, benthic carnivores; PAR, photosynthetically active radiation.

Fig. 4.

Variation in the effect of species richness on biomass as a function of (A–D) environmental drivers and (E) geography. Shown are standardized partial regression coefficients (β) from the hierarchical model, with coefficients estimated separately by ecoregion. P < 0.001 for all relationships.