Biodiversity Promotes Stability

Whether variety helps or hinders the stability of ecosystems has been the object of a long-standing debate in ecology, but Onofrio Mazzarisi, a researcher at the ICTP’s Quantitative Life Sciences section and at the National Institute of Oceanography and Applied Geophysics – OGS, is among the authors of a new study published in the prestigious journal Science on 15 March 2024 showing that diversity promotes the stability of ecosystems. The collaboration involved researchers from Canada, France, Germany, Italy and the US.

"In the presence of resources that support their existence, organisms belonging to the most diverse taxonomic groups reproduce exponentially. As the environment becomes more crowded, saturation is reached, and this dynamic is usually described by an 'S' curve, typical of the logistic model, which is the best-known and most widely used model in this field," explains Mazzarisi, who first-authored the study alongside Ian Hatton, a research associate at McGill University, Canada. "We instead used a model where the damping of the exponential growth phase is more gradual than is usually assumed in this context. The model we used is widely applied to describe the growth of a single organism, from birth to maturation."

Crucially, this choice of model for the population dynamics shows that the more species compete against each other for resources in a certain ecosystem, the more stable the system becomes. Therefore, an increase in biodiversity brings stability, in contrast with most theoretical arguments formulated so far.

"To support our results, we used data on the abundance, growth and biomass of a wide variety of species - including insects, fish and mammals - from around the world and collected over the past 60 years," Mazzarisi adds.

The results of the study lead to the hypothesis that a large-scale loss of biodiversity could lead to reduced resilience of ecosystems.

In addition to ICTP, OGS and McGill University, the study involved researchers at the Max Planck Institute for Mathematics in the Science in Germany, the University of Kansas in the US, Université Paris Cité, PSL Research University and Capital Fund Management in France.