Action planning interventions to promote individual and collective climate action

People are increasingly concerned about climate change but under-engaged in climate action, especially collective action. Online interventions can support action planning and behavior change in contexts including pro-environmental behavior. However, psychological interventions have tended to focus on individual-level climate action, and we do not yet know how effective they are for collective actions. We tested whether action planning interventions based on mental contrasting with implementation intentions and episodic simulation could increase intentions to engage in individual (e.g., driving less) and collective (e.g., contacting elected officials about climate change) climate actions. Participants were randomly assigned to an individual action planning (IAP) intervention, a collective action planning (CAP) intervention, or a no-intervention control group, and rated intentions to engage in individual and collective pro-environmental behaviors after completing the intervention. Preregistered analyses (on N = 1,586 participants) showed that compared to the control group, both action planning interventions increase targeted pro-environmental behaviors. Furthermore, these effects spilled over to other (non-targeted) pro-environmental behaviors, but spillover effects only occurred within action types (individual vs. collective). CAP also had greater overall effects on the perceived impact of actions, including individual actions. This study extends prior theorizing about the psychology of action planning to incorporate collective actions and provides practical insights to bridge the gap between climate concern and engagement in coordinated climate initiatives.