A systematic literature review of voluntary behaviour change approaches in single use plastic reduction.

Plastic waste is a leading contributor to climate change due to its build up in landfill and oceans, releasing harmful greenhouse gases and causing harm to ecosystems. The past decade has seen a rise in the number of policies and legislative regulations surrounding the use of single-use plastics (SUP). Such measures are needed and have shown effectiveness in the reduction of SUP's. However, it is becoming apparent that voluntary behaviour change efforts, which preserve autonomous decision making are also needed to further reduce demand for SUP. This mixed-methods systematic review had three aims, 1) synthesise existing voluntary behavioural change interventions and approaches aimed at reducing SUP consumption, 2) assess the level of autonomy preserved in interventions, and 3) assess the extent of theory use in voluntary SUP reduction interventions. A systematic search was executed across six electronic databases. Eligible studies were peer-reviewed literature published in English between 2000 and 2022 reporting on voluntary behaviour change programs aimed at reducing the consumption of SUPs. Quality was assessed using the Mixed Methods Appraisal Tool (MMAT). Overall, 30 articles were included. Due to the heterogenic nature of outcome data in included studies, meta-analytic analysis was not possible. However, data were extracted and narratively synthesised. Communication and informational campaigns were the most common intervention approach with most interventions taking place in community or commercial settings. There was limited theory use among included studies (27% used theory). A framework was created using the criteria outlined by Geiger et al. (2021) to evaluate level of autonomy preserved in included interventions. Overall, level of autonomy preserved in included interventions was low. This review highlights the urgent need for more research into voluntary SUP reduction strategies, increased integration of theory in intervention development, and higher levels of autonomy preservation in SUP reduction interventions.