On Farmland and Floodplains-Modeling Urban Growth Impacts Based on Global Population Scenarios in Pune, India

Emerging megacities in the global south face unprecedented transformation dynamics, manifested in rapid demographic, economic, and physical growth. Anticipating the associated sustainability and resilience challenges requires an understanding of future trajectories. Global change models provide consistent high-level urbanization scenarios. City-scale urban growth models accurately simulate complex physical growth. Modeling approaches linking the global and the local scale, however, are underdeveloped. This work introduces a novel approach to inform a local urban growth model by global Shared Socioeconomic Pathways to produce consistent maps of future urban expansion and population density via cellular automaton and dasymetric mapping. We demonstrate the approach for the case of Pune, India. Three scenarios are explored until 2050: business as usual (BAU), high, and low urbanization. After calibration and validation, the BAU scenario yields a 55% growth in Pune's population and 90% in built-up extent, entailing significant impacts: Pune's core city densifies further with up to 60,000 persons/km(2), adding pressure to its strained infrastructure. In addition, 66-70% more residents are exposed to flood risk. Half of the urban expansion replaces agriculture, converting 167 km(2) of land. The high-urbanization scenario intensifies these impacts. These results illustrate how spatially explicit scenario projections help identify impacts of urbanization and inform long-term planning.