Plastic action or distraction? Marine plastic campaigns influence public engagement with climate change in both general and engaged audiences

Climate change poses a key threat to marine ecosystems globally. Yet, contemporary discussions on marine conservation and individual action tend to focus on small lifestyle changes such as reducing plastic use. Some question whether campaigns that target "low impact" behaviours such as those related to plastic distract from broader sustainability goals such as mitigating climate change. However, others suggest that promoting simple behaviours may cause "behavioural spillover", where simple behaviours influence the adoption of additional and potentially more impactful behaviours. Across two experimental surveys (N1 =581, N2 =572), in the context of the Great Barrier Reef, we test whether messages targeting plastic behaviours can influence the adoption of a range of climate-related behaviours, from reducing personal emissions to urging local representatives to take action on climate change. We find that messages which focus on plastic pollution can potentially lead to an increase in climate behaviours, particularly when past behaviours are made salient. However, we find no positive effects for already engaged audiences. Our findings suggest caution when developing plastic messaging strategies for reef conservation when behavioural spillover is the central goal.