Safeguarding Food Security is the Key to Unlocking the Land-Use Trilemma and Enabling Climate–Biodiversity Policy Synergies

The growing reliance on land-based approaches for climate mitigation and biodiversity conservation intensifies global competition for finite land resources. However, their compounded food-security impacts remain inadequately assessed because most evidence evaluates climate and biodiversity objectives in isolation. Here we employ an integrated global biosphere management modelling framework that incorporates biodiversity-priority layers and Gaussian-process emulation to quantify trade-offs among land-sector net greenhouse-gas (GHG) emissions, biodiversity intactness (BII) and food security. Results show that combined climate-biodiversity strategies effectively curb emissions and slow biodiversity loss, yet simultaneously increase global food prices by 57% and leave 368 million more people undernourished by 2050 compared to the baseline case, primarily in vulnerable Global South regions. The emulator reveals strongly non-linear trade-offs, with undernourishment accelerating as mitigation stringency increases and steepening under stricter protection as land competition displaces agriculture. While financial compensation equivalent to 0.39% of global Gross Domestic Product has proven potential to narrow the global North-South food-security divide, implementation schemes can be refined through collaborative global efforts to fully unlock its value. These findings necessitate coordinated biodiversity and climate governance that reconciles planetary boundaries with human welfare, highlighting the urgent need for technical and financial innovations to decouple nutrition security from cropland expansion.