Climate & Environment
Spillover Effect
Definition
A spillover effect is an impact of an activity or intervention experienced by parties outside its direct scope: knowledge spillovers from innovation, demand effects rippling through supply chains, conservation benefits leaking beyond protected area boundaries, or negative spillovers such as displaced deforestation (leakage), pollution crossing borders, or demand rebound. In impact evaluation, spillovers determine whether measured effects are attributable net benefits or partly displaced from elsewhere.
References
This reference provides supporting context for how “Spillover Effect” is defined and used.
Source imported for editorial provenance.
Overview
How it is used
The concept structures cost-benefit analysis, impact evaluation design, leakage accounting in carbon and deforestation policy, and the EU's trade-environment agenda.
Why it matters
Sustainability is a systems problem; spillovers are how the system answers back when we optimise only the part we can see.