By Jeff Kapembwa

What many perceive climate change as a passing phase, is now a contrast as its extremes now pose food insecurity caused by salinisation (salt water) and reducing crop yield, losses, the United Nations food agency-FAO attests.

Its major assessment of salt-affected soils in 50 years shows that nearly 1.4 billion hectares of land (just over 10 percent of the total global land area) are already impacted by salinity, with an additional one billion hectares at risk due to the climate crisis and human mismanagement.

In Africa, an estimated 16% of the total land area is degraded with salt. When non-productive land, like desert and salt pans, is excluded, the percentage rises to 22%.

South Africa’s salt-affected soils, derived from complex geological formations and soil forming processes, comprise almost 32% of the country’s surface area.

In Tanzania, more than 2 million ha of land are salt-affected, of which 1.7 million ha are saline soil and 0.3 million ha are sodic soil.

The climate crisis and human mismanagement are contributing to excessive salinisation, which, according to the report, affects more than 10 percent of the total global land area.

Ten 10 countries (Afghanistan, Australia, Argentina, China, Kazakhstan, the Russian Federation, the United States, Iran, Sudan, and Uzbekistan) account for 70 percent of the world’s salt-affected soils.

The Global Status of Salt-Affected Soils report presented during the International Soil and Water Forum 2024 in Bangkok co-organized by FAO and Thailand’s Ministry of Agriculture and Cooperatives exposed glaring soil and water degradation in the past 50 years.

The meeting sought to moot an urgent action plan for halting and reversing soil degradation and water scarcity.

Arguably, scientific findings show that excess salinity reduces the fertility of soils and severely impacts environmental sustainability.

In the countries most affected by this issue, salinity stress can lead to crops yield losses – such as rice or beans – of up to 70 percent. This, apparently, comes at a time when there is an urgent need to boost food production to feed a growing global population wallowing in poverty.

According to findings, there is estimated area of salt-affected soils at 1 381 million ha (Mha), or 10.7 percent of the total global land area.

An additional estimate o that 10 percent of irrigated cropland and 10 percent of rain-fed cropland are affected by salinity, although uncertainty remains high due to limited data availability.

Models of global aridity trends indicate that, under the existing trend of temperature increase, the affected area may increase to between 24 and 32 percent of the total land surface.

The vast majority of aridification is expected to occur in developing countries.

Causes:

Natural and human activities are main drivers of the salinisation. The climate crisis is increasing aridity and freshwater scarcity.

Rising sea levels are projected to place more than one billion people in coastal zones at risk of progressive flooding and salinisation by the end of the century.

Global warming is contributing to salinisation through the thawing of permafrost. Inadequate agricultural practices also play a significant role.

These include irrigating crops with poor-quality water, inadequate drainage, deforestation and the removal of deep-rooted vegetation, excessive water pumping in coastal and inland areas, the overuse of fertilisers, de-icing agents, and mining activity.

Global freshwater use, in particular, has increased six-fold during the last century, contributing to groundwater salinisation due to the overexploitation of aquifers for irrigation purposes.

Call for Action:

Since salt-affected soils account for at least 10 percent of land, their sustainable management is crucial to meet growing food demands.

The report offers a series of strategies for managing salt-affected soils sustainably.

Mitigation strategies include mulching, using interlayers of loose material, installing drainage systems and improving crop rotations.

Adaptation strategies include breeding salt-tolerant plants (such as halophyte.

These flourish in mangrove swamps, tropical sand and cliff shorelines, and even salt deserts) and bioremediation – using bacteria, fungi, plants or animals to remove, destroy or sequester hazardous substances from the environment.

By highlighting the critical link between sustainable soil management, water quality, and food production, “the report outlines strategies for the recovery of agricultural salt-affected soils, including emerging fields like saline agriculture and salinity bioremediation,” Lifeng Li, Director of FAO’s Land and Water Division, and Jorge Batlle-Sales, Chair of the International Network of Salt-affected Soils (INSAS), wrote in its Forward.

The report seeks a legal framework at the national and international levels to safeguard natural saline ecosystems and ensure the sustainable management of agricultural soils under irrigation, particularly in areas at risk of salinisation.

The action is to protect productivity, quality, and overall soil health, ensuring food quality and quantity for future generations.

Water reports

The Bangkok conference also witnessed the release of the report by FAO.

The first shows trends in water-use efficiency at global, regional and national levels, offering insights into the progress achieved and providing recommendations to accelerate efforts towards the sustainable use of water resources.

The second progress report examines trends in pressure on renewable freshwater resources from the economic sectors at a global, regional and national level.

The report highlights the challenges faced by regions where water stress levels are critical, particularly in terms of food security.

The progress reports address SDG indicators – 6.4.1 and 6.4.2, for which FAO is the custodian agency.

Both indicators are critical for agricultural productivity and resilience, as well as for food security, ecosystem balance, and enhanced climate resilience.

How salt water affects Crop Yield:

• Reduces water availability: Excess salts in the soil can prevent plant roots from accessing water, even if there is water in the soil. This is similar to the effects of drought, causing plants to wilt, turn brown, and eventually die.

• Toxic salts: Some salts are toxic to plants in high concentrations.

• Accumulates in soil: Salts are left in the soil after irrigation water evaporates or is used by plants. Over time, these salts accumulate and can prevent crops from growing.

• Reduces crop yield: If salts accumulate to damaging levels, they can reduce crop yield.

To prevent salt buildup, you can leach salts from the root zone by applying enough water so that some of it percolates through and below the roots.

The amount of salt that accumulates in the soil depends on the salinity of the water and the leaching fraction.

Some crops are more tolerant to salt than others. For example, potatoes are considered to be the most tolerant to saline water. These salts will reduce crop yield if they accumulate in the rooting depth to damaging concentrations.

The crop removes much of the applied water from the soil to meet its evapotranspiration demand (ET) but leaves most of the salt behind to concentrate in the shrinking volume of soil water.

Water quality and crop production

This is directly related to the quantity of salts dissolved in the irrigation water. All irrigation water contains potentially injurious substances.

Abstract:

Salts can be deposited in the soil from wind and rain, as well as through the weathering of rocks. These processes, combined with the influence of climatic and landscape features and the effects of human activities, determine where salt accumulates in the landscape.

When the accumulated salt in soil layers is above a level that adversely affects crop production, choosing salt-tolerant crops and managing soil salinity are important strategies to boost agricultural economy.

Worldwide, more than 800 million hectares of soils are salt-affected, with a range of soils defined as saline, acidic-saline, alkaline saline, acidic saline-sodic, saline sodic, alkaline saline sodic, sodic, acidic sodic and alkaline sodic.