Joint action for climate mitigation and biodiversity conservation may undermine global food security

In the future, agricultural land use is expected to continue expanding to meet the increasing food demand driven by population and economic growth. However, policy actions aimed at addressing climate change and biodiversity loss may impose constraints this expansion, leading to a triple land-use conflict. By linking land conservation priority data with the global economic land-use model (GLOBIOM), this study assesses the climate mitigation potential, biodiversity benefits, and food security risks under land-based climate mitigation and biodiversity conservation measures. The results indicate that dual measures could contribute to a cumulative carbon reduction of 242 Gt between 2020 and 2050, while maintaining global biodiversity integrity at 2020 levels by 2050. However, this would require a reduction in agricultural land use before mid-century, leading to a 57% increase in global food prices by 2050 compared to the baseline scenario and an additional 368 million people at risk of undernurishment, compared to 257 million under only climate mitigation measures. This is primarily due to the significant amplification effect of BECCS on food security under the land protection expansion scenario. Extensive scenario simulations based on Monte Carlo sampling reveal a nearly linear relationship between the carbon reduction potential of land-based measures and the resulting additional undernurishment risks, while the marginal biodiversity benefits decrease, further highlighting the "impossible trinity" of climate mitigation, biodiversity conservation, and food security arising from land-use conflicts. Although this study suggests that global food aids or agricultural subsidies could address the side effect at a cost of around 0.39% of GDP, the actual potential for food assistance remains limited.