Global biodiversity indices are used to measure environmental change and progress towards conservation goals, yet their fitness for purpose is poorly understood. Few indices have been evaluated comprehensively for their capacity to detect trends of interest, such as declines in threatened species or ecosystem function. Using a structured approach based on decision science, we evaluated nine indices commonly used to track biodiversity at global and/or regional scales against five criteria relating to objectives, design, behaviour, incorporation of uncertainty, and constraints (e.g. costs and data availability). We identified four key gaps in indices assessed: i) pathways to achieving goals (means objectives) are not always clear or relevant to outcomes decision makers wish to achieve (fundamental objectives); ii) index testing and understanding of expected behaviour is often lacking; iii) uncertainty is seldom acknowledged or accounted for; and iv) costs of implementation seldom considered. These gaps may render indices inadequate in certain decision-making contexts and are problematic for indices linked with biodiversity targets and sustainability goals. Ensuring index objectives are clear and their design is underpinned by a model of relevant processes are crucial in addressing the gaps identified by our assessment. Uptake and productive use of indices will be improved if index performance is rigorously tested, and assumptions and uncertainties are clearly communicated to end-users. This will increase the value of indices in accurately tracking biodiversity change and supporting national and global policy decisions, such as the post-2020 global biodiversity framework of the Convention on Biological Diversity. Article impact statement: Evaluating biodiversity indices against criteria testing fitness for use means more effective and robust application in decision-making. This article is protected by copyright. All rights reserved.

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利用决策科学评估全球生物多样性指数

全球生物多样性指数用于衡量环境变化和实现保护目标的进展，但人们对其适用性知之甚少。很少有指数对其检测感兴趣的趋势的能力进行了全面评估，例如受威胁物种或生态系统功能的下降。我们使用基于决策科学的结构化方法，根据与目标、设计、行为、不确定性的纳入和约束（例如成本和数据可用性）相关的五个标准，评估了通常用于在全球和/或区域范围内跟踪生物多样性的九个指标。我们确定了评估指标中的四个关键差距：i) 实现目标的途径（手段目标）并不总是明确或与决策者希望实现的结果（基本目标）相关；ii) 通常缺乏对预期行为的指标测试和理解；iii) 不确定性很少被承认或解释；iv) 很少考虑实施成本。这些差距可能使指数在某些决策环境中不充分，并且对于与生物多样性目标和可持续性目标相关的指数来说是有问题的。确保指标目标明确且其设计以相关流程模型为基础，对于解决我们评估中发现的差距至关重要。如果对指数的表现进行严格测试，并将假设和不确定性清楚地传达给最终用户，则指数的吸收和生产使用将得到改善。这将增加指标在准确跟踪生物多样性变化和支持国家和全球政策决策方面的价值，例如《生物多样性公约》的 2020 年后全球生物多样性框架。文章影响声明：根据测试适用性的标准评估生物多样性指数意味着在决策中更有效、更稳健地应用。本文受版权保护。版权所有。