This news release is available in Japanese.
Ecological communities around the world are richly varied, but a new study finds that many of these diverse communities follow an unexpected, yet consistent pattern: where prey are abundant, there are not proportionally more predators. Instead, as prey biomass increases, the ratio of predator-to-prey biomass decreases. This pattern was systematically identified across different areas, including grasslands, forests, lakes, and oceans, revealing an underlying structural organization of ecosystems. Pinpointing underlying structures such as this one is important as such structures regulate many of the goods and services that ecosystems provide, such as carbon sequestration and food production, Just Cebrian explains in a related Perspective. To examine ecological trends on a grand scale, Ian Hatton et al. analyzed biomass and production measurements of tens of thousands of populations across 2,260 ecosystems in 1,512 distinct locations globally. The authors note a clear pattern of biomass scaling, with an exponent consistently near ¾, where there the biomass of predators is threefold less than the biomass of prey. Similar changes are also observed when comparing per capita productivity and biomass, implying that in the absence of predators, prey populations increase if food is available, but with an ever-diminishing tendency. The authors suggest that competition for resources and other negative interactions among prey species may be contributing to the sublinear scaling observed.
Article #8: "The predator-prey power law: Biomass scaling across terrestrial and aquatic biomes," by I.A. Hatton; T.J. Davies at McGill University in Montréal, QC, Canada; K.S. McCann; J.M. Fryxell at University of Guelph in Guelph, ON, Canada; M. Smerlak at Perimeter Institute for Theoretical Physics in Waterloo, ON, Canada; A.R.E. Sinclair at University of British Columbia in Vancouver, BC, Canada; A.R.E. Sinclair at Tanzania Wildlife Research Institute in Arusha, Tanzania; M. Loreau at CNRS in Moulis, France.