Assessing adaptation and migration options for global coastal farmers facing sea-level rise

Global flood and salinity risk is increasing due to sea-level rise (SLR). Farmers in coastal areas will experience this risk through rising salinity levels that reduce crop yields and direct flood damage to their property. In response, farmers can take various actions such as protecting their homes, changing cropping patterns, or migrating to safer areas if adaptation is not feasible. We developed the agent-based model (ABM) called DYNAMO-M to assess these responses and their influence on climate risk for farmers. This is a global ABM that simulates the actions of 13 million farming households based on economic decision theory across 674 coastal zones from 2015 to 2080. Results show that globally, 23 billion USD of private farming assets will be at risk annually, and coastal areas of Florida, New York, and Oregon in the United States, as well as the coasts of Spain, France in Europe, Japan, China, Indonesia, and the Philippines in Asia, Brazil and Australia will experience significant farmer outmigration to inland regions. Under the RCP4.5-SSP5 scenario, approximately 518,000 farming households are projected to migrate, with the highest numbers in East Asia and the Pacific (about 376,000 households), followed by South Asia (about 86,000 households). The highest household adaptation rates (over 40%) are observed in Indonesia, parts of Africa (e.g., Nigeria, Mozambique), Argentina, and some Mediterranean regions. However, many farmers in these areas cannot adapt due to limited income. Such budget constraints are not limited to poorer countries. The United States also shows a high percentage of households unable to afford adaptation. Our findings suggest that small government subsidies can significantly enhance the adaptive capacity of poorer households, partially offsetting migration flows and increases in climate risk. Results indicate that globally, about 15,000 fewer households migrate when provided with 30% insurance coverage. Government subsidies that reduce farmers’ adaptation costs by 30% decrease global farmer migration by up to 10% in some floodplains. These findings are useful for informing migration policies, options for managed retreat, and efforts to reduce the burden on receiving areas while supporting vulnerable, often impoverished, communities in coastal zones.