Species richness and identity both determine the biomass of global reef fish communities

Jonathan S Lefcheck,Simon J Brandl,Amanda E Bates,Conor Waldock,J Emmett Duffy,Scott D Ling,Graham J Edgar,Aneil F Agrawal,Rick D Stuart-Smith,Stuart Kininmonth,Douglas B Rasher

doi:10.1038/s41467-021-27212-9

Abstract

Changing biodiversity alters ecosystem functioning in nature, but the degree to which this relationship depends on the taxonomic identities rather than the number of species remains untested at broad scales. Here, we partition the effects of declining species richness and changing community composition on fish community biomass across >3000 coral and rocky reef sites globally. We find that high biodiversity is 5.7x more important in maximizing biomass than the remaining influence of other ecological and environmental factors. Differences in fish community biomass across space are equally driven by both reductions in the total number of species and the disproportionate loss of larger-than-average species, which is exacerbated at sites impacted by humans. Our results confirm that sustaining biomass and associated ecosystem functions requires protecting diversity, most importantly of multiple large-bodied species in areas subject to strong human influences.

Highlights

Changing biodiversity alters ecosystem functioning in nature, but the degree to which this relationship depends on the taxonomic identities rather than the number of species remains untested at broad scales
Even as observational evidence supports strong links between species richness and ecosystem functioning, biomass production[7], it remains unclear how much of this relationship stems from reducing the number of species versus the specific traits proxied by the identities of species
One useful approach is to mathematically partition the total change in an aggregate property, such as community biomass, into component factors[11,12,13,14,15]. Inspired by these earlier approaches, we present a partitioning of the difference in standing stock biomass between pairs of communities—a reference site vs. a comparison site—into five additive components representing the effects of both gains and losses in species richness and composition, and the effects of any remaining influences such as environmental and ecological factors that are not already captured in the elements of community diversity

Summary

Introduction

Changing biodiversity alters ecosystem functioning in nature, but the degree to which this relationship depends on the taxonomic identities rather than the number of species remains untested at broad scales. Even as observational evidence supports strong links between species richness and ecosystem functioning, biomass production[7], it remains unclear how much of this relationship stems from reducing the number of species (at random) versus the specific traits proxied by the identities of species This distinction is important if extinctions are biased towards individual species that contribute disproportionately to functioning, such as large-bodied fishes[8]. One useful approach is to mathematically partition the total change in an aggregate property, such as community biomass, into component factors[11,12,13,14,15] Inspired by these earlier approaches, we present a partitioning of the difference in standing stock biomass between pairs of communities—a reference site vs a comparison site—into five additive components representing the effects of both gains and losses in species richness and composition, and the effects of any remaining influences such as environmental and ecological factors that are not already captured in the elements of community diversity. This term reflects the change in biomass between communities that is attributable to the kinds of species that are absent rather than the number of absent species

Objectives

Methods

Results