A Global Systems Perspective on Food Demand, Deforestation and Agricultural Sustainability

Feeding a larger and wealthier global population without transgressing ecological limits is increasingly challenging, as rising food demand (especially for animal products) intensifies pressure on ecosystems, accelerates deforestation, and erodes biodiversity and soil health. We develop a stylized, spatially explicit global model that links exogenous food-demand trajectories to crop and livestock production, land conversion, and feedbacks from ecosystem integrity that, in turn, shape future yields and land needs. Calibrated to post-1960 trends in population, income, yields, input use, and land use, the model reproduces the joint rise of crop and meat demand and the associated expansion and intensification of agriculture. We use it to compare business-as-usual, supply-side, demand-side, and mixed-policy scenarios. Three results stand out. First, productivity-oriented supply-side measures (e.g. reduced chemical inputs, organic conversion, lower livestock density) often trigger compensatory land expansion that undermines ecological gains-so that supply-side action alone cannot halt deforestation or widespread degradation. Second, demand-side change, particularly reduced meat consumption, consistently relieves both intensification and expansion pressures; in our simulations, only substantial demand reductions (on the order of 40% of projected excess demand by 2100) deliver simultaneous increases in forest area and declines in degraded land. Third, integrated policy portfolios that jointly constrain land conversion, temper input intensification, and curb demand outperform any single lever. Together, these findings clarify the system-level trade-offs that frustrate piecemeal interventions and identify the policy combinations most likely to keep global food provision within ecological limits.