GC21E-08 Easing the Tension in Land-Use Allocation Scenarios: Assessing Economic Driven Land-Use Scenarios Across Diverse Local-scale Earth-system Outcomes

Abstract: Aggressive mitigation pathways prescribe substantial reallocation from grazed to natural grasslands, creating competing demands and feedbacks between climate responses, carbon mitigation, food security, biodiversity, and infrastructure. However, existing land-use allocation frameworks rarely resolve the mechanisms by which these transitions occur. To address this gap, we integrated an economic-based land-use model from the Economic Projection and Policy Analysis (EPPA) model with a downscaling framework (Demeter) to generate regionally-specific, grid-level projections under contrasting scenarios, and further propagate the land-use results through the Community Earth System Model (CESM) to assess climate and carbon feedbacks (2000-2050).

Economic pressures systematically drive land-use intensification: high-pressure scenarios show pronounced transitions toward grazing at forest expense, while low-pressure scenarios favor stability. Regional heterogeneity is substantial—African transitions are predominantly forest-to-grazing, whereas the Americas show grazing expansion from natural grasslands and croplands. These divergent pathways produce directionally consistent but magnitude-variable responses: forest-to-grazing reduces GPP/NPP while increasing runoff and carbon loss, whereas crop-to-grazing shows opposing effects, though all show net vegetative carbon reductions. Thus, our impacts reflect directional robustness with uncertain magnitude.

A key limitation has emerged: grazed land is treated as static with NPP reduction controlled by an invariant "grazing intensity" parameter. Holding grazing intensity constant despite varying allocations prevents distinguishing increased extent from management intensity changes. In light of this, we conduct sensitivity analyses through systematically varying grazing intensity with biophysical effects across these scenarios. By considering grazing allocation (from EPPA) with grazing intensity (specified in CESM), we isolate management intensity's contribution and determine whether regional food-production versus carbon-sequestration and climate-feedback trade-offs reflect biophysical limits or management practices, enhancing predictive capacity for land-use and climate policy assessment.