Islands are increasingly used to protect endangered populations from the negative impacts of invasive species. Quarantine efforts on islands are likely to be undervalued in circumstances in which a failure incurs non-economic costs. One approach to ascribe monetary value to such efforts is by modeling the expense of restoring a system to its former state. Using field-based removal experiments on two different islands off northern Australia separated by > 400 km, we estimate cane toad densities, detection probabilities, and the resulting effort needed to eradicate toads from an island. We use these estimates to conservatively evaluate the financial benefit of cane toad quarantine across offshore islands prioritized for conservation management by the Australian federal government. We calculate density as animals per km of freshwater shoreline, and find striking concordance of density estimates across our two island study sites: a mean density of 352 [289, 466] adult toads per kilometre on one island, and a density of 341 [298, 390] on the second. Detection probability differed between our two study islands (Horan Island: 0.1 [0.07, 0.13]; Indian Island: 0.27 [0.22, 0.33]). Using a removal model and the financial costs incurred during toad removal, we estimate that eradicating cane toads would, on average, cost between $22 487 [$14 691, $34 480] (based on Horan Island) and $39 724 [$22 069, $64 001] AUD (Indian Island) per km of available freshwater shoreline. We estimate the remaining value of toad quarantine across islands that have been prioritized for conservation benefit within the toads’ predicted range, and find the net value of quarantine efforts to be $43.4 [28.4–66.6] – $76.7 [42.6–123.6] M depending on which island dataset is used to calibrate the model. We conservatively estimate the potential value of a mainland cane toad containment strategy – to prevent the spread of toads into the Pilbara Bioregion – to be $80 [52.6–123.4] – $142 [79.0–229.0] M. We present a modeling framework that can be used to estimate the value of preventative management, via estimating the length and cost of an eradication program. Our analyses suggest that there is substantial economic value in cane toad quarantine efforts across Australian offshore islands and in a proposed mainland containment strategy.

中文翻译：

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估计隔离的好处：消除岛屿上的入侵性蟾蜍蟾蜍

越来越多的岛屿被用来保护濒临灭绝的人口免受入侵物种的负面影响。在失败导致非经济成本的情况下，对岛屿的检疫工作可能会被低估。将货币价值归于此类工作的一种方法是对将系统恢复到其先前状态的费用进行建模。通过在距澳大利亚北部200公里以外的两个不同岛屿上进行基于野外的清除实验，我们估算了甘蔗蟾蜍的密度，检测概率以及从岛上消灭蟾蜍所需的工作量。我们使用这些估算值来保守地评估澳大利亚联邦政府优先考虑进行保护管理的各个近海岛屿上的甘蔗蟾蜍检疫的财务收益。我们将密度计算为每公里淡水海岸线的动物数量，并发现我们两个岛屿研究点的密度估计值惊人地一致：一个岛上每公里的平均密度为352 [289，466]蟾蜍每公里，第二个岛上的密度为341 [298，390]。我们两个研究岛之间的检测概率有所不同（霍兰岛：0.1 [0.07，0.13]；印度岛：0.27 [0.22，0.33]）。使用去除模型和去除蟾蜍的财务成本，我们估计，消除甘蔗蟾蜍的平均费用为22487美元[14 691美元，34 480美元]（基于霍兰岛）和39 724美元[22 069美元，64 001美元]可用淡水海岸线每公里AUD（印度岛）。我们估计在岛屿的蟾蜍检疫工作中，其剩余价值已被优先考虑以保护其利益，因此发现检疫工作的净价值为43.4美元[28.4-66.6] – 76美元。7 [42.6–123.6] M，具体取决于用于校准模型的孤岛数据集。我们保守地估计，一个内地甘蔗蟾蜍遏制策略的潜在价值–防止蟾蜍扩散到Pilbara生物区–分别为80美元[52.6–123.4] – 142美元[79.0–229.0]M。我们提出了一个建模框架，可以通过估算消灭计划的时间和成本来估算预防性管理的价值。我们的分析表明，在澳大利亚近海岛屿的甘蔗蟾蜍检疫工作和拟议的内地遏制战略中，具有重要的经济价值。我们保守地估计，一个内地甘蔗蟾蜍遏制策略的潜在价值–防止蟾蜍扩散到Pilbara生物区–分别为80美元[52.6–123.4] – 142美元[79.0–229.0]M。我们提出了一个建模框架，可以通过估算根除计划的时间和成本来估算预防性管理的价值。我们的分析表明，在澳大利亚近海岛屿的甘蔗蟾蜍检疫工作和拟议的内地遏制战略中，具有重要的经济价值。我们保守地估计，一个内地甘蔗蟾蜍遏制策略的潜在价值–防止蟾蜍扩散到Pilbara生物区–分别为80美元[52.6–123.4] – 142美元[79.0–229.0]M。我们提出了一个建模框架，可以通过估算根除计划的时间和成本来估算预防性管理的价值。我们的分析表明，澳大利亚近海岛屿的甘蔗蟾蜍检疫工作和拟议的内地遏制战略都具有重大的经济价值。