1. Key Centre for Biodiversity and Bioresources, Department of Biological Sciences, Macquarie University, New South Wales 2109, Australia
2. Environmental Science, School of Botany, University of Melbourne, Parkville, Victoria 3052, Australia
3. Applied Biomathematics, 100 North Country Road, Setauket, New York 11733, USA
4. Present address: Key Centre for Tropical Wildlife Management, Northern Territory University, Darwin, Northern Territory 0909, Australia

Correspondence to: Barry W. Brook^1,2 Correspondence and requests for materials should be addressed to B.W.B. (e-mail: Email: barry.brook@ntu.edu.au).

Abstract

Population viability analysis (PVA) is widely applied in conservation biology to predict extinction risks for threatened species and to compare alternative options for their mangement^{1, 2, 3, 4}. It can also be used as a basis for listing species as endangered under World Conservation Union criteria⁵. However, there is considerable scepticism regarding the predictive accuracy of PVA, mainly because of a lack of validation in real systems^{2, 6, 7, 8}. Here we conducted a retrospective test of PVA based on 21 long-term ecological studies—the first comprehensive and replicated evaluation of the predictive powers of PVA. Parameters were estimated from the first half of each data set and the second half was used to evaluate the performance of the model. Contrary to recent criticisms, we found that PVA predictions were surprisingly accurate. The risk of population decline closely matched observed outcomes, there was no significant bias, and population size projections did not differ significantly from reality. Furthermore, the predictions of the five PVA software packages were highly concordant. We conclude that PVA is a valid and sufficiently accurate tool for categorizing and managing endangered species.