As soil salinization intensifies, it poses serious threats to ecosystems, soil health, global food security and socio-economic stability.
By Nima Shokri, Amirhossein Hassani and Muhammad Sahimi, EOS
Soil salinization refers to the excess accumulation of salt in soil to a level that affects crop production and ecosystem functioning. This poses serious threats to sustainable agriculture, soil fertility and health, food security, and socio-economic stability.
A new article in Reviews of Geophysics explores the complex dynamics of soil salinization around the globe. We asked the authors to give an overview of soil salinization, its impacts, and what questions remain.
Are certain regions of the world particularly susceptible to soil salinization?
Soil salinization is a global issue but especially prevalent in arid and semi-arid regions. According to a report by the Food and Agricultural Organization of the United Nations (FAO) and the Intergovernmental Technical Panel on Soils (ITPS), about one‐third of the world’s irrigated land is affected by salt.
Recent estimates have identified significant areas of salinization in the Middle East and North Africa, Central Asia, Australia, Southern Europe, the southwestern United States, and parts of South America.
What are the main drivers of soil salinization?
Soil salinization can be due to natural or anthropogenic factors, referred to as primary and secondary soil salinization, respectively. In naturally-occurring or primary soil salinization, the predominant origins of soluble salts include soil attributes, parent materials, climate, and land cover. In anthropogenic or secondary soil salinization, sources of soil salinization include industrial processes and mining that increase salt content of soil, and agricultural practices that are not sustainable.
How do scientists observe and monitor soil salinization at different scales?
A combination of field measurements, remote sensing technology, and modeling techniques can be used. For example, field-based measurements involve collecting soil samples from different depths to analyze salt concentration and electrical conductivity (EC) in the laboratory, which help assess the extent of salinization. Remote sensing techniques offer significant potential for monitoring soil salinization on regional and global scales by analyzing surface reflectance patterns. Additionally, a wide range of modeling approaches and GIS-based tools can be employed to describe and predict salinization across different areas and scales.
How is climate change expected to influence soil salinization?
The problem of soil salinization is expected to worsen due to projected climate variability and the increasing occurrence of extreme weather events.
The problem of soil salinization is expected to worsen due to projected climate variability and the increasing occurrence of extreme weather events. Shifts in the frequency, intensity and duration of these events will lead to changes in the factors driving soil salinization. For instance, changes in precipitation patterns affect the soil’s leaching capacity, a key mechanism for regulating salinity. Rising summer temperatures will increase evapotranspiration, leading to higher salt concentrations in the soil.
Other climate-driven factors include salt intrusion into coastal aquifers due to sea level rise and windborne salt distribution caused by altered wind patterns. Additionally, land use changes and more frequent extreme events, such as prolonged droughts followed by severe floods, may release and redistribute salts from geological substrates, exposing new areas to the risk of salinization.
What are some of the negative impacts of increased soil salinity on the environment, ecosystems, and human health?
Soil salinization has significant implications for ecosystem functioning, crop productivity, and socio-economic stability.
High salinity in the root zone severely hampers plant growth, resulting in reduced crop yields. Additionally, salt stress can drastically decrease plant transpiration, influencing the hydrologic cycle.
Soil salinity also creates nutrient imbalances in plants, affecting Earth’s organisms and ecosystems, and limiting both natural growth and agricultural production. Excessive salinity reduces the functioning of soil microbial communities, disrupting the nitrogen cycle and soil respiration. Other negative effects include salt storms, desertification, and changes to the soil organic carbon cycle.
In agriculture-dependent economies, soil salinization can diminish crop yields, reduce farmers’ incomes, and lead to food shortages, impacting related sectors like food processing and distribution. In severe cases, it can harm human health and economic well-being, resulting in unemployment, forced migration, and social instability.
What can be done to address this major global challenge of soil salinization? Who should take action?
Addressing this global challenge requires a multifaceted approach involving various stakeholders. Sustainable agricultural practices, such as implementing efficient irrigation systems, can help to mitigate salinity. Additionally, soil management techniques such as leaching, mulching, and soil conservation could be employed.
Governments should develop and enforce policies promoting sustainable land and water management, possibly providing financial incentives to farmers adopting these practices. Meanwhile, investment in scientific research is essential for innovation and knowledge dissemination. Community engagement through awareness campaigns can educate the public on the impacts of salinization and encourage sustainable practices. Finally, international collaboration and funding from global organizations are crucial for sharing resources, data and technology to combat soil salinization.
What are some of the unresolved questions where additional modeling, data or research efforts are needed?
There are several challenges in understanding soil salinity. For instance, considerable uncertainty exists in estimating the total area of salt-affected soils. Additionally, there is a non-uniform distribution of ground-based measurements of soil salinity, with the majority of data coming from Europe and North America. This bias can affect the accuracy of global- scale modeling.
There is also a lack of information and data on secondary salinization processes. The interaction between climate and soil salinization requires further investigation too. Lastly, the sharing of locally measured data between different nations presents another challenge, making it difficult to obtain an accurate global picture. Each of these areas need additional research and attention.
—Nima Shokri (nima.shokri@tuhh.de; 0000-0001-6799-4888), Hamburg University of Technology, Germany; Amirhossein Hassani (0000-0002-6470-0490), Norwegian Institute for Air Research, Norway; and Muhammad Sahimi (0000-0002-8009-542X), University of Southern California, USA
Citation: Shokri, N., A. Hassani, and M. Sahimi (2024), Soil salinization: a rising threat to ecosystems and global food security, Eos, 105, https://doi.org/10.1029/2024EO245029. Published on 21 October 2024.
