Chadès Iadine, McDonald-Madden Eve, McCarthy Michael A, Wintle Brendan, Linkie Matthew, Possingham Hugh P
Unité de Biométrie et Intelligence Artificielle, Institut National de la Recherche Agronomique, Unité Mixte de Recherche 875, BP 27 F-31326 Castanet-Tolosan, France.
Proc Natl Acad Sci U S A. 2008 Sep 16;105(37):13936-40. doi: 10.1073/pnas.0805265105. Epub 2008 Sep 8.
Threatened species become increasingly difficult to detect as their populations decline. Managers of such cryptic threatened species face several dilemmas: if they are not sure the species is present, should they continue to manage for that species or invest the limited resources in surveying? We find optimal solutions to this problem using a Partially Observable Markov Decision Process and rules of thumb derived from an analytical approximation. We discover that managing a protected area for a cryptic threatened species can be optimal even if we are not sure the species is present. The more threatened and valuable the species is, relative to the costs of management, the more likely we are to manage this species without determining its continued persistence by using surveys. If a species remains unseen, our belief in the persistence of the species declines to a point where the optimal strategy is to shift resources from saving the species to surveying for it. Finally, when surveys lead to a sufficiently low belief that the species is extant, we surrender resources to other conservation actions. We illustrate our findings with a case study using parameters based on the critically endangered Sumatran tiger (Panthera tigris sumatrae), and we generate rules of thumb on how to allocate conservation effort for any cryptic species. Using Partially Observable Markov Decision Processes in conservation science, we determine the conditions under which it is better to abandon management for that species because our belief that it continues to exist is too low.
随着种群数量的减少，濒危物种越来越难以被发现。这类难以捉摸的濒危物种的管理者面临着几个困境：如果他们不确定该物种是否存在，是应该继续针对该物种进行管理，还是将有限的资源投入到调查中？我们使用部分可观测马尔可夫决策过程以及从解析近似中得出的经验法则，找到了这个问题的最优解。我们发现，即使不确定该物种是否存在，为难以捉摸的濒危物种管理保护区也可能是最优的。相对于管理成本而言，物种受到的威胁越大、价值越高，我们就越有可能在不通过调查确定其是否持续存在的情况下对该物种进行管理。如果一个物种一直未被发现，我们对该物种持续存在的信心会下降到某个程度，此时最优策略是将资源从拯救该物种转向对其进行调查。最后，当调查导致我们对该物种现存的信心足够低时，我们将资源转向其他保护行动。我们通过一个案例研究来说明我们的发现，该案例研究使用了基于极度濒危的苏门答腊虎（Panthera tigris sumatrae）的参数，并且我们生成了关于如何为任何难以捉摸的物种分配保护工作的经验法则。在保护科学中使用部分可观测马尔可夫决策过程，我们确定了在何种情况下最好放弃对该物种的管理，因为我们认为它继续存在的信心太低。
