Researchers from a major American university analyzed how human activity alters the natural salt cycle on Earth. Their assessment indicates that air, soil, and freshwater are becoming increasingly salty due to human influence. If this trend continues, it could pose a serious risk to ecosystems and public health. The findings appear in the scientific journal Nature Reviews Earth and Evolution (NREE).
Natural geological and hydrological processes slowly move salts to the planet’s surface over time. Yet activities such as mining and land development are speeding up this salt transfer, amplifying salinity far beyond natural rates.
Agriculture, urban development, water and road treatment, and other industrial operations contribute to higher salinity levels. In some cases, rising salinity damages biodiversity and can render drinking water unsafe for communities.
The study explored a range of salt ions that accumulate in underground and surface waters, offering a broader view than a simple focus on common table salt.
Lead author Sujay Kaushal notes that conventional thinking often centers on sodium chloride, but the research over several years shows increases in other salts linked to limestone, gypsum, and calcium sulfate. This expands the scope of salinization beyond the familiar compound.
Global estimates suggest anthropogenic salinization now covers more than one billion hectares of land, roughly the size of the United States. Over the past five decades, salinity in streams and rivers has risen. Salt particles have even reached the atmosphere, carried by winds from salty landscapes. In snowy regions, road salt spray contributes to salinity in air and water and can influence local climate patterns through aerosol formation.
Salinity changes trigger cascading effects. Salt dust may accelerate snowmelt, affecting communities that depend on snowpack for water. Salt ions can attach to contaminants in soils and sediments, forming complex mixtures that travel through water systems and impact ecosystems and human health alike.
Authors advocate for establishing planetary boundaries for sustainable salt use, akin to limits placed on carbon dioxide to address climate change. The goal is to balance development with the protection of freshwater resources and biodiversity.
Earlier studies highlighted protective strategies for salmon against harmful runoff from highways, illustrating how land-use practices can influence aquatic life and water quality. The current work broadens that perspective to emphasize salinization as a global, multi-faceted challenge that demands coordinated policy response and ongoing monitoring. Attribution: University of Maryland study on anthropogenic salinization and its planetary impact.