Evaluation of climate change impacts on soil loss in Saemangeum reclaimed coastal farmlands of Korea using the APEX model

This study evaluated the impacts of climate change on soil loss in the reclaimed coastal farmlands of South Korea using the Agricultural Policy/Environmental eXtender (APEX) model coupled with CMIP6-based multi-model ensemble (MME) climate projections.Two Shared Socioeconomic Pathways, SSP1-2.6 (low-emission) and SSP5-8.5 (high-emission), were analyzed for the near-future (2041 -2070) and far-future (2071 -2100) periods.Slope conditions were represented by three field treatments (0°, 3°, and 5°) established in large-scale reclaimed plots (40 × 45 m).To capture within-plot hydrologic variability and support slope-specific model calibration, soil water content was monitored at upper, middle, and lower sections for the 3° and 5° plots.The model demonstrated reliable performance, yielding coefficient of determination (R 2 ) values exceeding 0.5 across all slope conditions.Simulation results indicated that average soil loss increased with slope gradient and was substantially exacerbated under the high-emission scenario.Under SSP1-2.6, the mean annual soil loss for the 5° slope increased by 49.7%, from 1.49 t ha -1 yr -1 (2041 -2070) to 2.23 t ha -1 yr -1 (2071 -2100).Under SSP5-8.5, the same slope exhibited a 72.0%surge, rising from 1.51 to 2.59 t ha -1 yr -1 .Notably, even in flat areas (0°), soil loss increased by 22 -44% depending on the scenario.The majority of this erosion was concentrated during the summer months (July -August), driven by intensified monsoon rainfall.These results underscore the increasing vulnerability of reclaimed coastal farmlands to long-term climate change.Ultimately, this study provides quantitative evidence to support targeted policies for sustaining soil productivity, improving field drainage, and ensuring the long-term sustainability of coastal agricultural lands.