Editing Population viability analysis (section)

==Controversy==
{{Unreferenced section|date=April 2016}}
Debates exist and remain unresolved over the appropriate uses of PVA in conservation biology and PVA’s ability to accurately assess extinction risks.

A large quantity of field data is desirable for PVA; some conservatively estimate that for a precise extinction probability assessment extending ''T'' years into the future, five-to-ten times ''T'' years of data are needed.  Datasets of such magnitude are typically unavailable for rare species; it has been estimated that suitable data for PVA is available for only 2% of threatened bird species.  PVA for threatened and endangered species is particularly a problem as the predictive power of PVA plummets dramatically with minimal datasets.  Ellner et al. (2002) argued that PVA has little value in such circumstances and is best replaced by other methods.  Others argue that PVA remains the best tool available for estimations of extinction risk, especially with the use of sensitivity model runs.

Even with an adequate dataset, it is possible that a PVA can still have large errors in extinction rate predictions.  It is impossible to incorporate all future possibilities into a PVA: habitats may change, catastrophes may occur, new diseases may be introduced.  PVA utility can be enhanced by multiple model runs with varying sets of assumptions including the forecast future date.  Some prefer to use PVA always in a relative analysis of benefits of alternative management schemes, such as comparing proposed resource management plans.

Accuracy of PVAs has been tested in a few retrospective studies. For example, a study comparing PVA model forecasts with the actual fate of 21 well-studied taxa, showed that growth rate projections are accurate, if input variables are based on sound data, but highlighted the importance of understanding density-dependence (Brook ''et al.'' 2000).<ref name="Brook et al. 2000">{{cite journal |author1=Brook B.W. |author2=O'Grady J.J. |author3=Chapman A.P. |author4=Burgman H.R. |author5=Akçakaya H.R. |author6=Frankham R. | title=Predictive accuracy of population viability analysis in conservation biology| journal=Nature | year=2000 |volume=329|issue=6776 | pages=512–519|doi=10.1038/35006050 |pmid=10746724 |bibcode=2000Natur.404..385B |s2cid=4373715 }}</ref> Also, McCarthey ''et al.'' (2003)<ref name="McCarthy et al. 2003">{{cite journal |author1=McCarthy M.A. |author2=Andelman S.J. |author3=Possingham H.P. | title=Reliability of relative predictions in population viability analysis| journal=Conservation Biology | year=2003 | volume=17|issue=4 |pages=982–989 | doi=10.1046/j.1523-1739.2003.01570.x|s2cid=59427471 |url=http://espace.library.uq.edu.au/view/UQ:10197/Reliability_of_r.pdf }}</ref> showed that PVA predictions are relatively accurate, when they are based on long-term data. Still, the usefulness of PVA lies more in its capacity to identify and assess potential threats, than in making long-term, categorical predictions (Akçakaya & Sjögren-Gulve 2000).<ref name="Akçakaya & Sjögren-Gulve 2000">{{cite journal |author1=Akçakaya H.R. |author2=Sjörgren-Gulve P. | title=Population viability analysis in conservation planning: an overview| journal=Ecological Bulletins | year=2000 |volume=48|pages=9–21}}</ref>