The Unfolding Desert: Observed Structural Drying and Projected Aridity Risks in a Brazilian Family Farming Citizenship Territory

Aridification in Semiarid regions is a recurring theme in Intergovernmental Panel on Climate Change (IPCC) reports and has been documented in Northeastern Brazil. This study analyzes the spatiotemporal dynamics of aridification in the Lower São Francisco River “Citizenship Territory” (Sergipe and Alagoas) at a fine spatial resolution (~1 km). Regional bias correction was performed using historical meteorological data and WorldClim v2.1 raster images. The CMIP6/ACCESS‐CM2 model's performance was evaluated by comparing historical and projected trends in maximum and minimum temperatures and monthly precipitation across four Shared Socioeconomic Pathways (SSPs) and time periods (2021–2100). A regional ETA model coupled with HadGEM2ES highlighted limitations in detecting aridification at different spatial scales, with coarser models potentially underestimating aridity. Downscaling to 1 km revealed a cold bias for temperature and a dry bias for precipitation, which were corrected using station data. Historically, the region has experienced rapid warming (+0.41°C decade −1 for Tmax), with projected trends most closely matching the pessimistic SSP37.0 scenario (+0.455°C decade −1 ). Semiarid and Agreste zones showed faster aridification processes and declining minimum temperatures, indicative of ongoing aridification. Evidence suggests that, by the end of the century, the territory shifts from a dry sub‐humid to a predominantly Semiarid annual regime, with at least 3 months per year reaching arid conditions, thereby threatening water resources and agricultural productivity. These results emphasize the urgent need for adaptation strategies and public policy interventions. The predominance of family farming, low Human Development Index, and socioeconomic vulnerability in the Citizenship Territory further justify alignment with the IPCC's principles of climate justice and just transition.