Most modern-day environmental issues are caused by the complex aggregation and interaction of numerous actions contributing to large-scale problems, from biodiversity loss to climate change. Environmental impact assessments (EIAs) consider how projects contribute to these cumulative environmental problems. This article firstly evaluates the theoretical importance of cumulative effects concepts for EIA. It reveals their potential to spotlight values embedded in decision making and to illuminate, as a lighthouse would, types of harm from broad-ranging, typically unregulated, activities. A large-scale global survey of national EIA laws and multilateral environmental agreements then shows that cumulative effects concepts are legally relevant for most national EIA frameworks. This prevalence suggests that better implementation of cumulative effects provisions may help EIA law to deliver more significant benefits than previously appreciated. Evaluating a sample of EIA provisions shows that cumulative effects concepts can contribute to different stages of an EIA, but that using these concepts across all EIA stages would maximize their potential to achieve the theoretical benefits identified. From theoretical and practical legal perspectives, cumulative effects concepts have significant latent potential – perhaps transformational potential – to address cumulative environmental change through EIA regimes at national and international levels. However, without better implementation, the latent potential of these laws to address cumulative environmental problems is likely to remain unrealized. By shedding light on the extent of national and international legal frameworks that adopt cumulative effects concepts, and their differences, this article highlights the significant learning potential between legal regimes to aid improved implementation.

大多数现代环境问题都是由导致从生物多样性丧失到气候变化等大规模问题的众多行动的复杂聚集和相互作用引起的。环境影响评估 (EIA) 考虑项目如何导致这些累积的环境问题。本文首先评估了累积效应概念在 EIA 中的理论重要性。它揭示了它们有潜力突出决策制定中嵌入的价值，并像灯塔一样照亮广泛的、通常不受监管的活动造成的危害类型。一项针对国家环境影响评估法律和多边环境协议的大规模全球调查表明，累积效应概念在法律上与大多数国家环境影响评估框架相关。这种普遍性表明，更好地实施累积影响条款可能有助于环境影响评估法带来比以前认为的更显着的好处。评估 EIA 规定的样本表明，累积效应概念可有助于 EIA 的不同阶段，但在所有 EIA 阶段使用这些概念将最大限度地发挥其实现所确定的理论效益的潜力。从理论和实践法律的角度来看，累积效应概念具有巨大的潜在潜力——也许是转型潜力——通过国家和国际层面的环境影响评估制度来解决累积环境变化。然而，如果没有更好的实施，这些法律解决累积环境问题的潜在潜力可能仍未实现。