Commonwealth Environment Research Facility (Applied Environmental Decision Analysis), School of Botany, University of Melbourne, Australia.
Conserv Biol. 2010 Aug;24(4):1111-8. doi: 10.1111/j.1523-1739.2010.01461.x. Epub 2010 Mar 5.
Statements of extinction will always be uncertain because of imperfect detection of species in the wild. Two errors can be made when declaring a species extinct. Extinction can be declared prematurely, with a resulting loss of protection and management intervention. Alternatively, limited conservation resources can be wasted attempting to protect a species that no longer exists. Rather than setting an arbitrary level of certainty at which to declare extinction, we argue that the decision must trade off the expected costs of both errors. Optimal decisions depend on the cost of continued intervention, the probability the species is extant, and the estimated value of management (the benefit of management times the value of the species). We illustrated our approach with three examples: the Dodo (Raphus cucullatus), the Ivory-billed Woodpecker (U.S. subspecies Campephilus principalis principalis), and the mountain pygmy-possum (Burramys parvus). The dodo was extremely unlikely to be extant, so managing and monitoring for it today would not be cost-effective unless the value of management was extremely high. The probability the Ivory-billed woodpecker is extant depended on whether recent controversial sightings were accepted. Without the recent controversial sightings, it was optimal to declare extinction of the species in 1965 at the latest. Accepting the recent controversial sightings, it was optimal to continue monitoring and managing until 2032 at the latest. The mountain pygmy-possum is currently extant, with a rapidly declining sighting rate. It was optimal to conduct as many as 66 surveys without sighting before declaring the species extinct. The probability of persistence remained high even after many surveys without sighting because it was difficult to determine whether the species was extinct or undetected. If the value of management is high enough, continued intervention can be cost-effective even if the species is likely to be extinct.
由于在野外对物种的不完全检测，灭绝的声明将永远是不确定的。在宣布一个物种灭绝时可能会犯两个错误。灭绝可能会过早宣布，从而导致保护和管理干预的丧失。或者，为了保护一个不再存在的物种，可能会浪费有限的保护资源。我们不是设定一个武断的确定性水平来宣布灭绝，而是认为这个决定必须权衡这两个错误的预期成本。最优决策取决于持续干预的成本、物种存在的概率以及管理的估计价值（管理收益乘以物种价值）。我们用三个例子来说明我们的方法：渡渡鸟（Raphus cucullatus）、象牙喙啄木鸟（美国亚种 Campephilus principalis principalis）和山地小袋鼠（Burramys parvus）。渡渡鸟极不可能存在，因此今天对其进行管理和监测是不划算的，除非管理的价值极高。象牙喙啄木鸟是否存在的概率取决于最近有争议的目击事件是否被接受。如果没有最近有争议的目击事件，在 1965 年宣布该物种灭绝是最优的。如果接受最近有争议的目击事件，最晚到 2032 年继续监测和管理是最优的。山地小袋鼠目前仍然存在，但目击率迅速下降。在宣布该物种灭绝之前，进行多达 66 次没有目击的调查是最优的。即使在多次没有目击的调查之后，持续的干预仍然可以是有成本效益的，因为即使物种可能已经灭绝，其生存的概率仍然很高。
