Three-Dimensional Ecological Footprint Assessment of Cropland in Typical Grain-Producing Regions Based on Carbon Footprint Improvement

The challenges of limited cropland resources and ecological degradation in grain-producing areas were addressed in this study within the broader context of China’s ecological civilization and dual carbon goals. An integrated framework was employed, applying the three-dimensional ecological footprint (EF3d) model, enhanced by carbon footprint improvement, to assess cropland at the provincial, municipal, and county levels. The analysis indicated a rise in both carbon absorption and emissions, resulting in a carbon surplus. Since 1984, chemical fertilizers have been identified as the predominant source of carbon emissions. Carbon absorption was found to vary distinctly among the four crops. Additionally, carbon fluxes displayed notable spatial and temporal variability. The ecological deficit persisted, showing distinct spatial clustering. Moreover, the cropland ecological footprint breadth (EFsize) was found to exhibit a pattern of decrease–increase–decrease, while cropland occupation remained high. The ecological footprint depth (EFdepth) consistently surpassed the threshold of 1. Spatially, the distribution pattern of cropland EFsize was opposite to that of EFdepth; the centroid of per capita cropland EFdepth underwent a significant spatial shift. The cropland EF3d was observed to experience a downward trend, with considerable regional disparities. Furthermore, unsustainable use of cropland was observed across multiple scales. This research provides an empirical foundation for promoting advancing ecological agriculture and sustainable cropland use practices.