The use and abuse of population viability analysis

A recent study by Brook ef al. empirically tested the performance of popula tion viability analysis (PVA) using data from 21 populations across a wide range of species. The study concluded that PVAs are good at predicting the future dynamics of populations. We suggest that this conclusion is a result of a bias in the studies that Brook et al, included in their analyses, We present arguments that PVAs can only be accurate at predicting extinction p robabilities if data are extensive and reliable, and if the distribution of vital rates between individuals and years can be assumed stationary in the future, or if any changes can be accurately predicted. In particular, we n ote th at although catastrophes are likely to have precipitated many extinc tions, estimates of the probability of catastrophes are unreliable.