The natural salt cycle of Earth, finely tuned over millennia, is currently undergoing significant disruption due to human activities on a global scale. Recent scientific investigations have uncovered this unsettling truth, prompting environmental scientists and policymakers to sound alarms about the repercussions of excessive salinization in ecosystems worldwide.
A comprehensive study published in the prestigious journal Nature Reviews Earth & Environment sheds light on how human activities, such as mining and road de-icing, are hastening salinization. This "anthropogenic salt cycle" is disturbing the slower geologic and hydrologic processes that traditionally regulate the movement of salt ions within the Earth's crust and water systems, posing a threat to biodiversity and human health.
Professor Sujay Kaushal of the University of Maryland, a lead author of the study, likens Earth to a living organism, with salt accumulation potent enough to "affect the functioning of vital organs or ecosystems." The study's authors express concern, suggesting that excessive salt accumulation could disrupt essential functions, much like how salt can affect vital organs in a living organism. Kaushal also highlights the energy-intensive and costly nature of desalination, the process of removing salt from water, and the environmental challenges posed by the highly saline byproduct.
The scale of human-induced salinization is staggering, with approximately 2.5 billion acres of soil—equivalent to the landmass of the United States—negatively impacted. There have also been significant increases in salt ions in rivers and streams over the past 50 years, mirroring trends in global salt production and consumption, indicating a direct link between human salt use and environmental impact.
Co-author Gene Likens reflects on the evolution of this research, noting that "twenty years ago, all we had were case studies." He emphasizes that the recent study highlights a global, interconnected cycle significantly disrupted by human activities.
In addition to affecting soil and freshwater systems, salts are being aerosolized, with saline dust contributing to snowmelt and creating "chemical cocktails" with contaminants, heightening environmental risks. In the United States, road salts—primarily used for de-icing—contribute significantly to this issue, accounting for a substantial portion of the total dissolved solids entering streams and waterways, with the U.S. producing 44 billion pounds of deicing salt annually.
Researchers have recommended policies to mitigate the influx of salt into water systems, including the use of alternatives like beet juice on roads. Kaushal emphasizes the importance of balancing immediate public safety concerns with the long-term health risks associated with excess salt in water. Drawing a parallel with climate change, the study's authors advocate for establishing a "planetary boundary for safe and sustainable salt use," similar to thresholds for carbon dioxide levels. While regulation presents challenges, Kaushal believes it is both feasible and necessary, as salt levels are indeed reaching environmentally harmful levels.