Population viability analysis (PVA) is widely applied in conservation biolo
gy to predict extinction risks for threatened species and to compare altern
ative options for their mangement(1-4). It can also be used as a basis for
listing species as endangered under World Conservation Union criteria(5), H
owever, there is considerable scepticism regarding the predictive accuracy
of PVA, mainly because of a lack of validation in real systems(2,6-8). 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 surprisin
gly accurate. The risk of population decline closely matched observed outco
mes, there was no significant bias, and population size projections did not
differ significantly from reality. Furthermore, the predictions of the fiv
e PVA software packages were highly concordant. We conclude that PVA is a v
alid and sufficiently accurate tool for categorizing and managing endangere
d species.