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Evaluation of Two Approaches to Defining Extinction Risk under the U.S. Endangered Species Act

机译：根据《美国濒危物种法》确定灭绝风险的两种方法的评估

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The predominant definition of extinction risk in conservation biology involves evaluating the cumulative distribution function (CDF) of extinction time at a particular point (the time horizon). Using the principles of decision theory, this article develops an alternative definition of extinction risk as the expected loss (EL) to society resulting from eventual extinction of a species. Distinct roles are identified for time preference and risk aversion. Ranges of tentative values for the parameters of the two approaches are proposed, and the performances of the two approaches are compared and contrasted for a small set of real-world species with published extinction time distributions and a large set of hypothetical extinction time distributions. Potential issues with each approach are evaluated, and the EL approach is recommended as the better of the two. The CDF approach suffers from the fact that extinctions that occur at any time before the specified time horizon are weighted equally, while extinctions that occur beyond the specified time horizon receive no weight at all. It also suffers from the fact that the time horizon does not correspond to any natural phenomenon, and so is impossible to specify nonarbitrarily; yet the results can depend critically on the specified value. In contrast, the EL approach has the advantage of weighting extinction time continuously, with no artificial time horizon, and the parameters of the approach (the rates of time preference and risk aversion) do correspond to natural phenomena, and so can be specified nonarbitrarily.
机译：在保护生物学中，灭绝风险的主要定义涉及评估在特定时间点（时间范围）的灭绝时间的累积分布函数（CDF）。本文运用决策理论的原理，将灭绝风险定义为由于物种最终灭绝而给社会带来的预期损失（EL）。确定时间优先和风险规避的不同角色。提出了这两种方法的参数的暂定值范围，并比较和对比了两种方法的性能，它们是针对一小部分具有已公布的灭绝时间分布的真实物种，以及一组假设的灭绝时间分布。评估每种方法的潜在问题，建议采用EL方法作为两者中的较好方法。 CDF方法遭受这样的事实，即在指定时间范围之前的任何时间发生的灭绝均被加权，而在指定时间范围之外发生的灭绝根本没有权重。还存在以下事实：时间范围与任何自然现象都不对应，因此不可能任意指定；但是结果可能严重取决于指定的值。相反，EL方法的优点是连续地对灭绝时间进行加权，没有人为的时间范围，并且该方法的参数（时间偏好率和风险规避率）确实与自然现象相对应，因此可以任意指定。

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