International climate adaptation assistance: Assessing public support in Switzerland

PLOS ONE | https://doi.org/10.1371/journal.pone.0317344 February 12, 2025 14 / 26 PLOS ONE Support for adaptation assistance in Switzerland Issue linkage with trade and UN voting alignment The results of the survey experiment show that Swiss respondents prefer adaptation policy packages for trading partners and for countries that vote with Switzerland in the UNSC. As shown in Fig 3, 80% alignment of votes with the Swiss position in the UN Security Council increases the favorability of policy packages, while the 0% alignment scenario reduces sup- port, with the mid-range (40%) being statistically non-significant (Hypothesis 3 is supported). Similarly, respondents favor policy packages for countries with medium and high levels of trade with Switzerland, while support is significantly reduced for countries with zero volume of trade (Hypothesis 4 is supported). These findings suggest that respondents tend to view climate adaptation assistance as part of the broader spectrum of international economic and policy engagement between Switzerland and developing countries – that is, they are not com- partmentalizing climate policy. The significant impact of the high share of UN vote alignment and high volumes of trade on public willingness to support adaptation packages to developing countries suggests that the public may view such countries as strategic allies in international affairs more broadly and with respect to climate adaptation more specifically. These findings prompted us to further

explore how such two-level issue-linkage might condition the effects of other conjoint attri- butes. Importantly, similar results were found in the case of Japan for vote alignment in the UN General Assembly, and countries to which Japan has a high volume of exports. The signif- icance of these factors across the different political contexts of two donor countries, in terms of trading partners, geographies, and policies related to climate, migration, and economic development, suggests that two-level issue linkage deserves further exploration with respect to public motivation to support for increasing adaptation assistance. Notably, the results on the conditional effects of trade volume and vote alignment in the UN Security Council provide further evidence of the significance of trade relations and UN Security Council position alignment for respondents’ preference of policy packages. As shown in Figs 3 and 4, the highest bilateral trade volume (1,000 million) is associated with a positive shift in respondents’ favorability of substantial bilateral aid packages, rang- ing from 30mn/year to 90mn/year. Similarly, respondents tend to favor packages with low and medium levels of climate migration (250 to 750 per year). By contrast, when there are no trading relationships, respondents are indifferent about policy packages containing 0 million of climate aid (the confidence interval overlaps the dashed line at 0.5, indicating indifference). Policy packages with positive levels of climate aid reduce respondents’ favor-

ability towards policy packages. These results are broadly robust to a different modeling strategy, specifically, nonparametric ANOVA regression [91], allowing the selection of the most important interaction effects between the different conjoint attribute levels (Support- ing information S17–S19 Tables, S20 Fig, S21–S22 Tables). These results show that policy packages in which countries do not trade with Switzerland decrease the policy package’s favorability in almost all treatment combinations of the attribute levels in the conjoint survey experiment. Fig 4 further shows that the conditional effect of an 80% alignment of votes with the Swiss position at the UN Security Council increases the favorability of policy proposals with the highest range of bilateral climate aid packages (90mn/year and 120mn/year), as well as for packages with low- and medium-level migration (250–750 persons/year). Significantly, the interaction with high levels of UN Security Council alignment and trade volumes makes respondents more likely to favor a broader range of countries (Philippines, Bangladesh, and Kenya). By contrast, the conditional effect of 0% alignment in the UN Security Council is associ- ated with negative or non-significant favorability for packages. These results strengthen our