First attempt at mapping the historical spatial distribution of rice cultivation after 1945 in Slovakia from military topographic maps

Abstract

We present the first Slovak national-scale reconstruction of post World War II rice cultivation in Slovakia using two military cartographic series (Military topographic mapping 1:25,000 – VTM25, 1952–1957; and 1:10,000, 1958–1971 – VTM10). Rice-field polygons were manually digitized strictly where the specific rice symbol occurs. We further verified the cartographic interpretation via a hydrotechnical case study (Zalaba project plans) and screened national WMTS tiles with a high-recall YOLOv5 utilized as a completeness check. We also cross-checked for positional error using independent church-tower control points (RMSE ≈ 18.5–21.5 m). We delineate 434 fields in 50 municipalities (2,297.7 ha) on VTM25 and 147 fields in 10 municipalities (254.34 ha) on VTM10, revealing a sharp post-1960 contraction with only ~11% of area persisting. LiDAR (1-m DTM) confirms preserved irrigation system fragments at several sites. Together, these lines of evidence show a brief expansion peak in the late 1950s followed by an abrupt termination, likely driven by policy and economics rather than local feasibility alone. We also highlight data limitations (symbol generalization, sheet-year asynchrony) and provide conservative area estimates. This national inventory provides a baseline for Central-European comparisons and for heritage-oriented conservation of agro-hydrotechnical relics.