On Evidence of Absence

When ACE-ÉCO received the submission by Hill et al., Evidence suggesting that Ivory-billed Woodpeckers (Campephilus principalis) exist in Florida, we faced a challenge. The Arkansas case is widely familiar (Fitzpatrick et al. 2005, Walters and Crist 2005, Fitzpatrick et al. 2006, Jackson 2006, Sibley et al. 2006) and highly politicized. One does not need to be a member of the ornithological community to appreciate that there might be further controversy generated by news of more putative observations of Ivory-billed Woodpeckers in Florida.


On Evidence of Absence De la certitude de l'absence
Thomas D. Nudds1 , Jeffrey R. Walters2 , and Marc- André Villard 3   When ACE-ÉCO received the submission by Hill et al., Evidence suggesting that Ivory-billed Woodpeckers (Campephilus principalis) exist in Florida, we faced a challenge.The Arkansas case is widely familiar (Fitzpatrick et al. 2005, Walters and Crist 2005, Fitzpatrick et al. 2006, Jackson 2006, Sibley et al. 2006) and highly politicized.One does not need to be a member of the ornithological community to appreciate that there might be further controversy generated by news of more putative observations of Ivory-billed Woodpeckers in Florida.
Neither did it escape our attention that the notoriety associated with the paper might be good for a fledgling journal.On the other hand, especially because of its political volatility, negative fallout from publishing the article might have dire consequences.Indeed, it is legitimate to ask whether the scientific bar has been adjusted for publicity, and whether it is productive-from a scientific perspective-to publish further papers claiming to have rediscovered Ivory-billed Woodpeckers without direct, physical evidence, such as clear photographs, videos, or feathers.
We promote ACE-ÉCO as intermediate in scope to journals with traditional emphases on basic ecology or management and conservation (Nudds and Villard 2005), and are careful nevertheless to put good science first; this implies embracing uncertainty (Villard and Nudds 2006).To deny publication of a controversial paper simply because it did not present a definitive conclusion to an ongoing debate with political consequences would only mean that we abrogated our responsibility.The subject matter is first and foremost consistent with our vision for ACE-ÉCO.
What is that responsibility, more specifically?Consider the scientific method: observations about nature generate hypotheses and predictions that are subjected to further scrutiny.This leads, through strong inference (Platt 1964, Chamberlin 1965), either to falsification of the hypotheses, or an increase in our confidence that the hypotheses can account for the observations.In this case, the null hypothesis seems clear: Ivory-billed Woodpeckers are not present-in Arkansas, Florida, or anywhere else for that matter.Some advocates may treat the alternative hypothesis-that Ivory-billed Woodpeckers are present, at least somewhere-as an article of faith, and skeptics will rightly point out that the evidence for this alternative hypothesis may be weak.From a scientific perspective, it seems safe to state that the observations do not allow rejection of the alternative hypothesis out of hand.Regardless, as Carl Sagan pointed out, absence of evidence is not evidence of absence.Hill et al. conclude that their evidence at least warrants an expanded search in space and time.We agree."Harder" physical evidence, such as photographs, would enable an unequivocal rejection of the null hypothesis.If no such evidence ever materializes, despite an expanded search effort, the alternative hypothesis is assessed just the same.Furthermore, Hill et al. offer new forms of evidence (cavity size distributions, putative foraging sites) that can be http://www.ace-eco.org/vol1/iss3/art3/assessed in other areas, including those in which Ivory-billed Woodpeckers clearly are absent.Thus, they provide both evidence consistent with the alternative hypothesis, and means to increase confidence in our inability to reject the null hypothesis.Science is a way of knowing, and knowing occurs either way.
Another responsibility of the journal is to provide an efficient medium for communication among those who must scrutinize the evidence.For the first time, sounds are directly appended to a paper.On the other hand, making this evidence quickly and widely accessible might also have dire consequences for the putative remnant population if it leads to uncoordinated and unregulated search efforts.Therefore, we asked the authors to take steps to guard against this.
By bringing this paper to the attention of avian ecologists and conservationists, ACE-ÉCO is participating in the scientific process of hypothesis generation and evaluation.As is the nature of our business, readers will decide for themselves.The online, open access format of the journal readily permits dialogue on this topic, and we invite readers to submit comments.For now, we are prepared to embrace the uncertainty presented by the evidence in Hill et al.Time, and rigorous testing, will be the ultimate judge.