Evaluating Climate Change Impacts on Water Resources and Food Systems – A Global Perspective with Insights from Africa and California.

This dissertation focuses on evaluating the hydrological impacts of climate change on water and food systems through integrated assessment models at various scales (global, country, and regional). The first chapter explores the future of global food self-sufficiency analysis in the 21st century under sustainable intensification of agriculture. By integrating biophysical, hydrological, climate, and societal models, the study considers factors such as sustainability, diet changes, population growth, agricultural intensification, and climate to project future scenarios. The findings reveal a concerning trend, indicating a probable decline in global food self-sufficiency within the middle-of-the-road and business-as-usual trajectories. In the second chapter, the focus shifts to Africa, a region experiencing high levels of food insecurity due to climate change and population growth. By assessing the impact of irrigation expansion on agricultural productivity and climate adaptation, the study highlights the limitations of irrigation alone in achieving food self-sufficiency. Under a 3°C warmer climate, Africa's total food production would only be sufficient to feed 1.35 billion people, while the population is projected to reach 3.5 billion. This underscores the need for additional strategies beyond irrigation alone to achieve food self-sufficiency, such as cropland expansion or increased reliance on imports. At a regional level, the third chapter employs Earth system models to assess the vulnerability of California's water-food nexus to changing snow regimes due to climate change. With a majority of snow monitoring sites showing declines in snowpack depths and earlier snowmelt onset, the study highlights the potential consequences of declining snowmelt on water availability for crop production, raising concerns about food security in a region already grappling with increased demand. This dissertation provides a comprehensive understanding of the complex dynamics influencing global food security. The findings emphasize the importance of sustainable practices, the limitations of irrigation expansion in addressing food deficits in Africa, and the vulnerability of water resources to declining snowpack in California. These insights contribute valuable knowledge for policymakers and stakeholders in formulating effective strategies to ensure a sustainable and secure food future for the global population