Soil Salinization Under Climatic and Management Drivers: A Multi-Scale Comparative Synthesis of Nine Long-Term Case Studies

Soil salinization affects more than 424 million hectares of topsoil worldwide and is associated with yield losses of 18–43% in drylands, yet its long-term dynamics have rarely been compared across regions on a common basis. This work synthesizes nine case studies from a systematic, PRISMA-guided search, selected purposively to maximize variation in climate, scale and method. ECe (dS/m) and total salt content (g/kg) have no general conversion, so the eight ECe-based studies are compared class by class using their own figures; the single g/kg study contributes direction only, and no values are pooled. The largest transfers occur between the intermediate and higher classes, while the non-saline class changes little in most settings; intensification of already salt-affected land therefore predominates over conversion of new land, though the latter also occurs (Bachu County). The drivers reported by the source studies are irrigation expansion, inadequate drainage, and shallow saline groundwater, with rising evaporative demand and reduced leaching as amplifiers; since no study partitions the change between climatic and management causes, this ordering is descriptive, not a causal attribution. The synthesis is hypothesis-generating; its main product is a direction-of-change summary table separating observed trends from projections.