Analysing patterns of vegetation cover after natural disturbances, such as nutrient or water shortages, could provide advanced warning of collapses in plant populations.

Richard Bailey at the University of Oxford, UK, used a computer model to look for signatures of population fragility in spatial and temporal patterns of semi-arid vegetation cover, which change as populations decline. He found that if a plant population's recovery rate reaches a 'critical slowdown' after a perturbation event, this provides an early warning of a fragile state from which it may never fully recover — it may either stabilize at a lower level or disappear.

Proc. R. Soc. B doi:10.1098/rspb.2010.1750 (2010)