‘Extinction-proof’ population sizes cannot be predicted from species traits

Threatened species are characterized by declining and eventually small numbers of individuals. Once a population has been reduced below a certain level, its chances of recovery are slim.

This size is commonly referred to as a ‘minimum viable population’, or MVP. But is there one size that fits all species, or are MVPs more idiosyncratic?

Many have shown that the relative susceptibility of species to human-caused decline and extinction can be predicted by traits such as body size, ecological specialization, dispersal ability, fertility, and so on.

However, a recent paper published in Ecology Letters by Brook, Traill and Bradshaw of Charles Darwin University in Australia shows that this is not true for MVP. By modelling the long-term monitoring data of 1198 species they reveal a wide range of MVPs which are strongly linked to local environmental variability but unrelated to intrinsic ecological attributes.

Any commonalities between species in MVP are swamped by the large-scale processes (e.g., habitat loss, over-exploitation) driving the global biodiversity crisis.