UC Berkeley

As climate hazards and their associated socioeconomic impacts become more severe, individuals and governments across the globe are reckoning with how best to adapt. For some, this might entail staying in place and altering their behaviors, livelihoods and investments as temperatures rise and rainfall becomes more variable. For others, however, the increased risk of physical harm, economic loss and social instability wrought by worsening climatic conditions may compel them to migrate in search of security elsewhere. Identifying how climate phenomena influence human movement can be straightforward, such as forced displacement that occurs following the physical destruction of a storm, flood or fire; however, in many instances, the climate-migration relationship is more opaque. Impacts on economic productivity, health and wellbeing from chronic stressors like drought, heatwaves, desertification and sea level rise may spur certain members of an afflicted region to out-migrate, while limiting the ability of others to do so, and will occur amidst a multitude of other, non-climatic influencing factors. Therefore, disentangling the manner and extent to which climate has driven human migration in the past, and the potential for it to do so in the future, is a challenging yet critical priority to shaping robust, proactive adaptation policies and humane migration governance frameworks moving forward.

This dissertation helps address this need by investigating the intersection of climate impacts, inequities and human displacement in various contexts. It is segmented into three distinct chapters based on relevance to i) Central America, ii) the United States and iii) global coastlines, regions in which climate-migration dynamics are likely to become increasingly relevant. The chapters are comprised of the following project-based subsections: (i) assessing 21st century drought projections in Central America’s Dry Corridor, which finds that seasonal and annual-scale droughts in the region are projected to lengthen, intensify and increase in frequency throughout the remainder of the century; (ii) modeling of international emigration and internal migration, as reported in the Guatemalan 2018 national census, using sociodemographic, physical and climatic covariates, finding various sociodemographic variables and drought stress as significant predictors of out-migration from the country; (iii) reviewing literature linking climate hazards, internal displacement, movement and inequities in the United States, which assesses the complex manner by which acute and chronic climatic hazards impact human displacement and exacerbate social inequality; (iv) producing high-resolution dasymetric maps of population in California using the 2020 census for various demographic subgroups, which are publicly available and useful in evaluating geospatial population distributions across the state for any number of research applications, and which to date have included numerous climate change, environmental justice and health equity studies; (v) conducting geospatial analysis of Hurricane Maria’s impact on Puerto Rican power supply, recovery and re-electrification and correlational relationships to subsequent out-migration, with constructed models explaining up to 82% of observed variance in post-storm power outage patters, indicating both physical and socioeconomic variables as being significant predictors of prolonged recovery; and (vi) creating an open-source coastal impacts and adaptation modeling platform along fine-scale global coastlines for multiple scenarios of 21st century sea level rise, which was used to inform the U.S. Environmental Protection Agency’s updated social cost of carbon estimate and suggests that, globally, between 16-46 million people are expected to relocate inland by 2100 if optimal adaptation strategies are undertaken and up to 200 million people under high-end sea level rise and sub-optimal adaptation pathways.