Climate change is manifesting itself in many ways. Salinization in soils is one of them, caused by rising sea levels and lower rainfalls. By degrading soil quality, it has a direct impact on the food of millions of people in the world. The UN Food and Agriculture Organisation (FAO) has developed a mapping tool to better identify the land at risk and define sustainable solutions in terms of irrigation and adaptation to climate change to favour the productivity of farmland.

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More than 8% of soils suffer from salinization

Almost a billion hectares of land worldwide (i.e., 8.7%) are affected by the phenomenon of salinization, mainly in arid and semi-arid areas in Africa, Asia and South America. This striking figure was taken from the world map drawn by the FAO with the support of 118 countries and hundreds of data collectors.

It also shows that 20 to 50% of irrigated land on all the continents is too salty. This means that more than 1.5 billion people in the world are faced with major challenges linked to food production, due to the degradation of soils.

A complex phenomenon

What has caused this accumulation of salt in the earth? Although salinization in natural habitats exists on every continent and in all climates, the extension and intensification of human activities causes what is called “secondary” salinization that aggravates primary salinization, degrades ecosystems that have been preserved up to now, and magnifies desertification. Salinization processes are complex, often linked to those of surface water and groundwater flows. But they are accelerated by poor irrigation practices or by soils rich in salts, intensive deforestation, or by certain fertilisers containing potassium salts and nitrates. Climate change aggravates the situation still further, with the intrusion of saltwater inland and in the groundwater used for irrigation, lower rainfalls, and the increased evaporation of freshwater.

This anthropic salinization modifies the composition of natural water in lakes, rivers and aquifers, and degrades the quality of the water used for different domestic, agricultural and industrial needs. It contributes to reducing biodiversity and soil fertility, thereby limiting exploitable agricultural and fish resources. Predictive analyses point to an increase of 23% of the surface area of arid zones – mainly in developing countries – by the end of the century.

Rice growing is particularly affected by salinization, reducing the living conditions of many populations in Africa and Asia who depend on rice for food and income. This situation may cause new migrations, as farmers leave in search of new arable land, and risks of conflicts over land, as is already the case in Gambia (read the article published in Le Monde: “Organising the combat against salinization in rice fields in Gambia”, on 3 January 2022).

How can land affected by salinization be recovered?

The FAO’s mapping tool makes it possible to localise sensitive areas,  and prevent salinization through mitigation measures, and the sustainable land management.

Although farmers have long adopted practices capable of controlling and reducing surplus salt (dissolution of salts via ample supplies of freshwater, drainage to eliminate salt from crop roots, etc.), new adaptive measures are henceforth needed. These include: