Application of salinization indicators and initial development of potential global soil salinization scenario under climatic change

Salt accumulation in soil is a global problem. This paper investigates salt‐affected soils on a global scale through spatial modeling within a Geographical information system (GIS). As salt‐affected soils arise due to a range of processes that can be very localized and complex in nature, three main indicators have been developed to provide insight into areas at risk of salinization at a global scale. At this scale, climate and topography are the main factors influencing solute accumulation. The paper derives salinity indicators from global data sets and compares them to independent maps of salt‐affected areas. The primary indicators are (1) low relief, (2) high two‐way annual moisture flux, and (3) local flow deficit in large catchments. The first two of these are related for conditions where there is potential for a large vertical flux of salts, and where groundwater levels may be high, providing conditions for salt accumulation locally or at the base of slope catenas. The third indicator is related to conditions where there is a risk of accumulation of salts in floodplains and adjacent irrigated areas. These salinity indicators are then estimated for future GCM scenarios of climate for 2079–2099. Comparison of the current and scenario indicator distributions shows that the areas at risk of salinization may increase globally, through both expansion of existing areas and the creation of new ones. Current distributions of risk, and to a greater extent future scenarios, are limited by the quality and resolution of available data, and have the potential for enhancement as these data improve.