IUCN / SSC Cat Specialist Group - Digital Cat Library |
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| Brook, B.W.; Burgman, M.A.; Ak‡akaya, H.R.; O'Grady, J.J.; Frankham, R. | |
| Critiques of PVA ask the wrong questions: throwing the heuristic baby out with the numerical bath water | |
| 2002 Conservation Biology (16): 262-263 | |
The analyses of Ellner et al. (2002 [this issue]), like those of Ludwig (1999) and Fieberg and Ellner (2000), suggest that although the predictions of population viability analyses (PVA) may be unbiased, the estimates of extinction risk are usually too imprecise to be worthwhile. Ellner et al. correctly reconcile the superficial discrepancies between Ludwig (1999) and Brook et al. (2000). But they then allude to the recent review by Coulson et al. (2001) that restates the widely held view (see also Harcourt 1995; Beissinger & Westphal 1998) that in circumstances where data are sparse or of low quality (commonly the case for threatened species), PVAs have little useful predictive value and should be dispensed with in favor of "alternative methods." The trouble is that none of these authors have specified why these alternatives would be superior to PVA. It is our view that even when PVAs perform poorly against some vaguely defined absolute standard, they still perform better than alternatives that are even more vague, are less able to deal with uncertainty, are considerably less transparent in their reliability, and do not use all the available information. |
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