Food security, encompassing physical, social, and economic access to sufficient, safe, and nutritious food, is a critical global challenge exacerbated by climate change. While most studies focus on climate change's impact on food supply (production), this research emphasizes the equally important role of demand-side factors, specifically dietary changes. The study's context lies in the growing global population and shifting dietary preferences towards more resource-intensive foods, particularly in developing nations. The increasing affluence of the middle class and globalization have driven dietary shifts towards higher proportions of carbohydrates and animal-based proteins. Although offering short-term health benefits, such diets have long-term sustainability concerns. This study addresses the gap in existing research by integrating supply-side impacts of climate change with demand-side changes caused by evolving dietary patterns. This integrated approach is crucial for a comprehensive understanding of food security under a changing climate and informs policy decisions for sustainable food systems.

Existing literature extensively documents the negative impacts of climate change on food supply, particularly reduced yields of major crops due to temperature increases and extreme weather events. Studies have shown climate change and variability negatively affecting food supply, though productivity gains from technological advancements previously offset weather impacts. However, these studies often lack a comprehensive account of anthropogenic dietary shifts, influencing food demand. Previous research has also focused on mitigating climate change through reducing GHG emissions. This study expands upon previous work by integrating both supply and demand-side dynamics in a global-scale analysis, providing a more holistic view of food security under climate change. This integrated approach addresses a critical gap in current knowledge, moving beyond myopic supply-side assessments to encompass the dynamic interplay of climate change and dietary transitions.

This study utilized a comprehensive dataset spanning 1990-2018 and projected to 2031-2060, incorporating country-level data from various sources: FAOSTAT for food supply (including trade data from WITS), Global Dietary Database 2018 (GDD2018) for dietary patterns, UN data for population projections, and NASA Power and CMIP6 models for climate data. The study employed a cereal equivalent (CE) coefficient to aggregate food supply and demand across different food categories, accounting for variations in resource use efficiencies. A panel model was used to estimate the impact of climate variables (temperature, precipitation, agricultural water input) and trade on CE food supply. Dietary changes' impact on food demand was assessed by comparing per capita demand changes in 2018 relative to 1990, accounting for population growth. Future projections integrated eight dietary change scenarios (including business-as-usual, traditional diets, recommended diets, and sustainable diets) with two SSP-RCP climate change scenarios (SSP2-4.5 and SSP5-8.5) to analyze food security under different pathways. The study identified six plausible scenarios for food security based on the interplay between climate change impacts on supply and dietary changes on demand. A key methodological aspect was the use of CE coefficients to account for resource-use differences between various food categories, enabling a more accurate comparison of climate and dietary impacts.

The analysis revealed a significant increase in per capita demand for most major food categories globally from 1990 to 2018, with notable increases in Asia for vegetables, meat, fish, eggs, and milk. Climate change negatively impacted food supply in 92% of countries during this period, although this impact was lower than reported in previous studies possibly due to technological advancements and international trade mitigating impacts. Integrating climate change impacts on food supply with dietary changes on demand showed that 70% of countries experienced negative impacts on food security, affecting 1.6 billion people. Scenario I, where climate change negatively impacted food supply while increasing food demand, affected nearly 60% of countries and 4.8 billion people. Future projections demonstrated that climate change will continue to reduce global food supply (by 3-4% under different scenarios), while a business-as-usual (BAU) dietary scenario will cause a substantial increase in demand (74%). Importantly, the study found that shifting towards sustainable diets (Flexitarian and EAT-Lancet) could significantly mitigate the negative impacts of climate change on food security.

This study highlights the inadequacy of focusing solely on climate change's impact on food production in food security assessments. The significant influence of dietary changes on food demand necessitates a holistic approach, integrating both supply and demand-side factors. The findings demonstrate that even positive impacts of climate change on food supply might be negated by increasing food demand driven by dietary shifts. The results stress the importance of promoting sustainable diets that are both nutritionally balanced and environmentally friendly. The mitigation potential of sustainable diets, such as reduced reliance on animal products, emphasizes the urgent need for dietary transitions. This research supports policy interventions focused on both climate change mitigation and promoting dietary shifts towards sustainable patterns to enhance global food security.

This study makes a crucial contribution by demonstrating the critical role of dietary changes in food security assessments under climate change. The integrated analysis reveals that neglecting demand-side factors significantly underestimates the challenges to food security. The findings highlight the potential of sustainable diets in mitigating these threats, emphasizing the need for policies promoting such dietary transitions alongside climate change mitigation strategies. Future research could explore the economic and social implications of dietary shifts, incorporating more detailed modeling of food markets and prices.

The study acknowledges limitations, including the exclusion of food waste, which accounts for a considerable portion of food demand. Furthermore, the model does not explicitly incorporate market prices and their influence on food trade and affordability. Data limitations, particularly in harmonizing food supply and demand data sources, may also affect the accuracy of the analysis. The use of CE coefficients, while improving resource-use comparisons, simplifies the complexity of diverse food systems. Finally, national factors beyond climate, such as economic policies and social structures, can also impact food demand patterns and were not explicitly integrated into the model.