Chapter 06 · Governance & regulationGovernance, Ethics & Risk
Cumulative impact
Definition
Cumulative impact (or cumulative effects) refers to the totality of impacts arising from the interaction of multiple past, present and reasonably foreseeable actions and stressors. The US Council on Environmental Quality defined cumulative effects in 1979 regulations; the US EPA's 2022 framing emphasises the combined burden of chemical and non-chemical stressors on communities, including social and economic stressors.
References
2022 definition
regulatory origin
practice distinction
Overview
What it means
A wetland lost here and a road built there may each look acceptable, while together they push an ecosystem or community past a threshold.
How it is used
Cumulative impact assessment extends project-level ESIA to valued environmental and social components (VECs) at regional scale; it is increasingly central to environmental-justice policy and strategic environmental assessment.
Why it matters
Project-by-project approval systematically underestimates harm; cumulative framing is the corrective that regulators and courts increasingly demand.