Among the instrumental value defenses for biodiversity conservation is the argument that biodiversity is necessary to support ecosystem functioning. Lower levels of biodiversity yield lower levels of ecosystem functioning and hence the inference that we should conserve biodiversity. In our book Defending Biodiversity: Environmental Science and Ethics, we point out three problems with this inference. (1) The empirical support for such an inference derives from experiments conducted on a very small set of ecosystem types (mainly grasslands and fresh water aquatic) and ecosystem functions (mainly nutrient uptake, biomass production, and decomposition rates). These experiments suffer from a number of largely unavoidable logistical constraints making the generality of their results questionable. (2) Even if the experimental results were unequivocal, their lack of external validity would still raise significant questions about how (if at all) these results apply to real world conservation problems. And (3) even if the experimental results were unequivocal and completely applicable to conservation problems, relying on such defenses implies other rational policy commitments that are at odds with other positions that environmentalists commonly take. Odenbaugh and I disagree largely about what inferences follow from these points rather than about the points themselves. I think that what follows is that if environmentalists want to use instrumental value defenses, then we need to accept that not all biodiversity is useful to us, and parts that are useful are not necessarily more useful than alternatives that might threaten biodiversity. I also think that the unpalatable implied commitments need to be taken seriously. This may mean that we environmentalists have to accept that biodiversity should not always be conserved, and that parts of the environmentalist agenda are little more than strong personal preferences that others need not respect. If environmentalists are willing to accept these conclusions, then there are no problems with relying on these instrumental value defenses, but I suspect that environmentalists are likely to be unhappy with such conclusions.

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生物多样性、生态系统功能和环保议程：对奥登堡的回复

在生物多样性保护的工具价值防御中，有一个论点是生物多样性是支持生态系统功能所必需的。较低水平的生物多样性产生较低水平的生态系统功能，因此推断我们应该保护生物多样性。在我们的《捍卫生物多样性：环境科学与伦理》一书中，我们指出了这一推论的三个问题。(1) 对这种推论的实证支持来自对极少数生态系统类型（主要是草地和淡水水生）和生态系统功能（主要是养分吸收、生物量产生和分解率）进行的实验。这些实验受到许多在很大程度上不可避免的后勤限制，使得其结果的普遍性值得怀疑。(2) 即使实验结果是明确的，他们缺乏外部有效性仍然会引发重大问题，即这些结果如何（如果有的话）适用于现实世界的保护问题。(3) 即使实验结果是明确的并且完全适用于保护问题，依赖这种防御意味着其他理性的政策承诺与环保主义者通常采取的其他立场不一致。奥登堡和我在很大程度上不同意从这些观点得出的推论，而不是观点本身。我认为接下来是，如果环保主义者想要使用工具性价值防御，那么我们需要接受并非所有生物多样性对我们都有用，有用的部分不一定比可能威胁生物多样性的替代品更有用。我还认为需要认真对待令人不快的隐含承诺。这可能意味着我们环保主义者必须接受生物多样性不应该总是得到保护，环保议程的一部分只不过是其他人不需要尊重的强烈个人偏好。如果环保主义者愿意接受这些结论，那么依赖这些工具性价值辩护就没有问题，但我怀疑环保主义者可能会对这样的结论不满意。