Cumulative effects: past present and foreseeable future – the state of the art

Cumulative effects assessment (CEA) has been part of impact assessment systems since the 1970s. Yet, practice often fails to address how multiple past, present, and foreseeable actions jointly affect the environment, people, and the rights of vulnerable groups and Indigenous Peoples. Informed by a literature review, this paper traces the origins of CEA regulation, guidance and practice in North America, Europe, and beyond. It shows that, despite global recognition, CEA remains constrained by inconsistent definitions, fragmented institutional responsibilities, insufficient provisions for transboundary CEA, data gaps, limited monitoring, dominance of siloed approaches, and focus on physical components. Looking ahead, the paper identifies priorities for strengthening CEA: clarifying responsibilities, enacting cumulative effects from local to international law and policy, integrating cumulative risk and climate effects to address compounding effects, improving data access and uncertainty treatment, and using Strategic Environmental Assessment (SEA) and spatial planning as primary arenas for regional CEA. Adopting interdisciplinary and transdisciplinary system-based approaches that explicitly engage marginalised groups will help account for cumulative effects on socio-economic, cultural and intangible components, including spiritual ones. The paper concludes that CEA is a holistic mindset that regulators, practitioners, proponents and society should adopt to guide the planning and management of human activities.