New paper on species extinction risk in Ecological Complexity

Ecological communities are buffeted by a variety of abiotic and biotic environmental disturbances over time, but the effects of this temporal environmental variance on patterns of biodiversity are often unclear. A new study by Tak, Ryan and collaborator James O’Dwyer (University of Illinois) in the journal Ecological Complexity addresses this problem by developing new theory on how temporal environmental variance affects the extinction risk of a species.

Using a new Markov chain population model and novel calculations, it was found that the mean time to extinction typically decreased with the strength of temporal environmental variance, such that the extinction risk increased. The biological intuition behind this is that temporal environmental variance causes greater variation in the net growth rate and hence abundance of a species, and this increases the probability that the abundance reaches zero during unfavorable environmental conditions.

The new results are relevant for the debate about mechanisms that determine the coexistence of species in ecological communities, and also for conservation of species in the context of increasing temporal variance produced by global environmental change.

Click here to read the new study.


In a forest, an insect outbreak is an environmental disturbance that changes the net growth rate of tree species. Sufficiently large fluctuations in growth rate over time can drive species extinct. This picture shows widespread mortality of lodgepole pine (Pinus contorta) in northern Colorado, caused by a pine beetle infestation.