More biodiverse ecosystems, containing a greater number and variety of species, are generally more productive and support more living mass (biomass). Despite significant advances in ecological theories and experiments, however, the influence of biodiversity on the structure and functioning of natural ecosystems has remained a subject of debate. 

This study involving BTO sheds light on this complex relationship and unveils a new fundamental rule in ecology. The authors developed innovative experiments to demonstrate that species richness generally has a positive impact on biomass stocks, but the effects observed in more complex natural ecosystems has been more mixed. The study reveals that much of the variation in the strength and direction of the effect of biodiversity can be predicted by a fundamental macroecological quantity: the scaling of species abundance with body mass.

Key findings from the study indicate that more diverse ecosystems tend to support a higher biomass because they are more likely to contain the numerically rare large bodied species (such as elephants) that contribute disproportionally to ecosystem function. Conversely, biomass remains unaffected by species richness in those organisms when there is little correlation between species size and abundance. These insights suggest that changes in species richness have predictable impacts on biomass, guided by underlying ecological principles. 

This breakthrough has significant implications for understanding and managing biodiversity in natural ecosystems and the key services these provide human society, from providing food to storing carbon. By predicting the effects of species richness
on biomass, the findings could provide a critical tool for conservation efforts and ecological restoration.

Despite advances in theory and experiments, how biodiversity influences the structure and functioning of natural ecosystems remains debated. By applying new theory to data on 84,695 plant, animal, and protist assemblages, we show that the general positive effect of species richness on stocks of biomass, as well as much of the variation in the strength and sign of this effect, is predicted by a fundamental macroecological quantity: the scaling of species abundance with body mass. Standing biomass increases with richness when large-bodied species are numerically rare but is independent of richness when species size and abundance are uncoupled. These results suggest a new fundamental law in the structure of ecological communities and show that the impacts of changes in species richness on biomass are predictable.