Can green defaults reduce meat consumption?

Meat consumption and production cause a significant share of greenhouse gas (GHG) emissions in the food sector. Behavioural food policy suggests the use of defaults – i.e., pre-setting a specific choice option – as an effective demand-side instrument to reduce meat consumption. This preregistered systematic review compiles, critically appraises, and synthesizes existing empirical evidence on such food defaults. Beyond that, potential effect moderators are explored. The systematic search yields twelve individual studies comprising sixteen different default interventions. We find that defaults are generally effective in nudging consumers to eat less meat. The studies’ risk of bias is assessed to be moderate. Yet, the effect size appears to be influenced by a range of moderators. In particular, the invasiveness of the default, the presentation of alternatives to choose from, and consumers’ gender and setting experience appear to moderate the effect. Overall, evidence is still limited, and heterogeneity in the design and implementation of interventions is large. Further research is needed to understand the impact of effect moderators and to assess the long-term and large-scale effectiveness. We conclude that defaults are a promising tool for climate-sensitive food policy, with more knowledge needed to profoundly inform policymakers and implementing actors.