Biodiversity lessens the risk of cascading extinction in model food webs

Due to the complex interactions between species in food webs, the extinctio n of one species could lead to a cascade of further extinctions and hence c ause dramatic changes in species composition and ecosystem processes. We fo und that the risk of additional species extinction, following the loss of o ne species in model food webs, decreases with the number of species per fun ctional group. For a given number of species per functional group, the risk of further extinctions is highest when an autotroph is removed and lowest when a top predator is removed. In addition, stability decreases when the d istribution of interaction strengths in the webs is changed from equal to s kew (few strong and many weak links). We also found that omnivory appears t o stabilize model food webs. Our results indicate that high biodiversity ma y serve as an insurance against radical ecosystem changes.