Equitable adaptation planning under deep uncertainty for the upper Vietnam Mekong Delta

The importance of considering equity in climate change adaptation planning is increasingly being acknowledged. A preferred adaptation strategy is one that not only yields robust outcomes under multiple futures, but also has a fair distribution of benefits and harms across affected actors. In this study we propose two complementary approaches for assessing the equity of impacts of adaptation strategies. First, in the explorative approach, we explore what different multi-actor inequality patterns might emerge under different policy and uncertainty scenarios. Put differently, we identify who benefits and who loses under which kind of circumstances. Second, in the normative approach, we attempt to rank alternative strategies based on their performance across uncertain futures. Identifying which strategy is more preferable requires us to define what kind of distribution is considered to be ‘good’. We thus employ six alternative distributive moral principles that each has its own maxim in justifying the moral righteousness of a distribution: utilitarianism, prioritarianism, sufficientarianism, envy measures, weighted utilitarianism, and the Rawlsian difference principle.

We apply both approaches to a case study on agricultural adaptation planning in An Giang and Dong Thap, two provinces in the upper Vietnam Mekong Delta. We develop an integrated assessment metamodel to assess the equity implications of six alternative adaptation strategies, including dikes (de)construction policies, fertilizer subsidy, and seeds upgrading. We evaluate the distributional impacts of the alternative strategies to 23 districts in the two provinces under a large number of strategic scenarios, i.e., combinations of policy scenarios and uncertain futures. From the explorative approach, we discover six distinctive inequality patterns and identify the strategic scenarios that give rise to each inequality pattern. We find a trade-off between districts located along the Mekong river and those located further away. In some strategic scenarios the former group of districts are substantially better-off than the latter, and vice versa.

From the normative approach, we find a mixed result of preferred strategies depending on what moral principle is being adopted. The dikes deconstruction policy in Dong Thap, which performs best from a utilitarian point of view, ranks fifth from a prioritarian perspective. Upgrading seed is the most preferred strategy from the prioritarian view, but it performs the worst when looked at from a sufficientarian point of view. We further find that the results from each principle are strongly affected by uncertainties. For example, the fertilizer subsidy policy ranks last in approximately 70% of the uncertain futures according to the sufficientarian principle, but it becomes the most preferable in the other 20% of the uncertain futures. Our findings further emphasize the simultaneous consideration of both uncertainties and alternative distributive principles in adaptation planning. By using multiple moral principles, we expand the information base upon which adaptation decisions are made, and thus minimizing potential surprises and unintended consequences from our choice.