Public understanding of climate change-related sea-level rise

studies and our own show that there is plenty of space to develop more in-depth understand- ing of how the public perceives the threat of sea-level rise. The present research revealed the unexpected finding that one key audience for public engagement with sea-level rise is the concerned public who overestimate sea-level rise by 2100 as being catastrophic (and scientifically implausible). While there are obvious dangers associ- ated with a public that underestimates or minimises the dangers of sea-level rise–such as not taking adaptation measures, or not supporting governments committed to mitigation and adaptation–there are also dangers associated with a public that overestimates sea-level rise. A focus on extreme (and often unsound) projections of sea-level rise can result in public anxiety and feelings of helplessness, rather than motivation to take action to mitigate and adapt [55, 56]. Nevertheless, the present research shows that publics are aware of, and concerned about, 21st century sea-level rise, which is already impacting on coastal dwellers and infrastructure. Any public engagement efforts will therefore need to be more focused and nuanced than rais- ing awareness of the issue, and could include, for example, provision of ongoing and credible sea-level rise information that is accessible to a wide range of publics and decision-makers. With the knowledge that overestimating can lead to failure to act, communicating with this segment of the audience could focus on providing scientifically plausible projections of sea-

level rise and communicating that both adaptation and mitigation–to avoid the most extreme sea-level rise scenarios–are necessary. Conclusion As noted by Akerlof [23] in relation to a project focused on community adaptation to sea-level rise, ‘communication programs and public consultation by governments can benefit from the use of survey data to support evidence-based decision-making’ (p 406). Overall, our survey findings indicate that New Zealanders have a tendency to overestimate the amount of sea-level rise possible by 2100, with those more likely to overestimate future projections tending to be most concerned about sea-level rise. They also have a mistaken association of sea-level rise with melting of sea ice, and judge global sea-level rise projections as higher, and more concern- ing, than national sea-level rise projections. Criticisms of the ‘deficit model’ of science communication show that encouraging action on an issue–such as sea-level rise–is not as simple as ensuring that publics are fully informed [57]. However, it is essential that publics have access to information that can inform their deci- sion making, particularly with an issue such as sea-level rise that has widespread consequences for coastal livelihoods. If publics have a better understanding of the scale and rate of sea-level rise projected over this century and beyond, and the adaptation measures necessary to respond to this, there is evidence they will be more willing to also adopt mitigation measures [58]. Hence, having publics informed about sea-level rise and its impact will enable them to be

involved in decisions about both adaptation and mitigation strategies; that is, to prepare for the 0.24 to 0.32 m of sea-level rise we know is coming by 2050, as well as to reduce greenhouse gas emissions to avoid the higher sea levels possible by 2100 and beyond. The inclusion of informed publics in these decisions (and discussions) is an essential part of democratic deci- sion making [59]. Supporting information S1 File. Representative and pilot surveys. Here we provide more detailed information about survey design and results. (DOCX) PLOS ONE Public understanding of climate change-related sea-level rise PLOS ONE | https://doi.org/10.1371/journal.pone.0254348 July 9, 2021 8 / 12