High-resolution remote sensing reveals medium-scale farms at the frontiers of agricultural change in Africa.

Abstract Agricultural expansion continues to reshape landscapes across Africa, yet how patterns of cropland change vary across farming systems of different scales remains poorly understood. Here, we combined annual high-resolution field boundary mapping from Planet imagery with an empirically derived field-to-farm size relationship to examine cropland dynamics, farm-scale patterns, and their environmental and socioeconomic correlates across Zambia from 2018 to 2024. Cropland expansion was highly spatially concentrated, with local expansion rates reaching up to 170 ha yr -1 within 0.05◦ (≈5.5 km) grid cells, and occurred primarily along the margins of established agricultural regions. Areas dominated by medium-scale farms exhibited substantially faster cropland growth than areas dominated by smallholder farms. Similarly, when field size was considered as a continuous variable, cells characterized by larger median field sizes showed markedly higher expansion rates, exceeding 35 ha yr -1 in some areas, whereas expansion rates in areas dominated by smaller fields were generally below 5 ha yr -1 . Meanwhile, stable croplands showed little evidence of widespread field consolidation, with approximately 84% of grid cells exhibiting field-size trends within ±0.05 ha yr -1 , suggesting limited evidence for farm-scale expansion through widespread field consolidation within existing croplands. Environ mental and socioeconomic analyses further indicated that land tenure, represented by the proportion of land under state tenure, was the factor most consistently associated with the prevalence of medium scale farms, whereas climate stability was more strongly associated with total cropland area than with farm-size composition. Together, these findings suggest that recent agricultural growth in Zambia has been closely associated with the increasing prevalence of medium-scale farming, while widespread field consolidation within existing croplands appears limited. More broadly, the study demonstrates how high-resolution Earth observation can provide spatially explicit evidence of agricultural transformation and emerging farm structures across rapidly changing African farming systems.