El Niño and the Invisible Threat
Rising salinity is not only an environmental problem, but an economic and social threat of alarming proportions. Farmland, rendered barren by salt accumulation, is bringing farmers to their knees, causing huge economic losses and jeopardizing the food security of entire regions. The phenomenon accelerates land degradation, pushing once fertile areas toward desertification and turning them into unproductive expanses.
A recent study, The El Niño Southern Oscillation and the salinity of land and water in the United States, published in PLOS ONE by Nicola Limodio, Filippo De Marco and Ilaria Dal Barco of Bocconi University highlights how El Niño climate oscillations can drastically alter the concentration of salts in soils and fresh water in the United States. Their findings reveal a significant impact: soil salinity increases by 21 percent in northern regions and decreases by 29 percent in southern areas. At the same time, freshwater salinity increases by 9 percent in warmer counties and decreases by 53 percent in colder counties.
Why does salinity matter?
Increased salinity is not just a chemical detail, but a real threat to ecosystems and agriculture. “Excess salt in soils alters the osmotic balance of plants, limiting their uptake of water and essential nutrients,” Nicola Limodio explains. “This can drastically reduce yields and, in severe cases, cause crop failure.” Salinity is also a major driver of desertification, turning once fertile land into barren expanses.
In addition to the impact on agriculture, the phenomenon also affects biodiversity. Increased salinity in fresh waters threatens the balance of ecosystems, altering species composition and reducing biodiversity. Agricultural practices, as a consequence, would be forced to change: rising temperatures and reduced rainfall, typical effects of El Niño, are pushing toward greater use of saline water sources, further exacerbating the problem.
El Niño, climate and salinity: a complex intertwining
The study shows that the interaction between El Niño, temperature, rainfall and salinity is more complex than previously imagined. Warmer and drier regions tend to experience an increase in salinity, while cooler and wetter regions see a decrease in salinity. “ENSO (El Niño-Southern Oscillation) directly affects the water cycle: heavy precipitation dilutes salt, while evaporation in arid areas concentrates it in soils and groundwater,” says Filippo De Marco.
During El Niño, the subtropical jet stream moves toward California, bringing heavy rainfall in southern regions and drought in northern regions. This shift has a direct effect on soil and water salinity, with implications far beyond the United States.
The signal of climate change
According to the researchers, salinity variation could be an indicator of the effects of climate change globally. “These data raise concerns not only for agriculture and ecosystems, but also for long-term food security,” Limodio warns. “If global warming continues to alter the frequency and intensity of El Niño, we can expect increasingly severe impacts on soil health and agricultural productivity.”
The study opens new perspectives on the need to monitor salinity changes more carefully and develop mitigation strategies to protect both the environment and economies dependent on agriculture. While the world focuses on temperature and precipitation, a silent enemy may already be at work beneath our feet.
