April 11, 2019 — The water tastes salty and the rice barely grows in the coastal villages of the Ca Mau peninsula at the southern tip of Vietnam's Mekong River delta.

Thi Tran, a young woman who farms ii acres (0.viii hectares) of rice and vegetables while her married man works on the line-fishing boats in the Gulf of Thailand, says she fears for her family.

"When we moved here 10 years ago it was OK to farm. But we struggle to grow anything at present and accept to buy fresh h2o," she says, speaking through a translator. "The soil and the water gets saltier. If I don't grow rice, I do not have anything to feed my family. We tin only use this water for gargling and cooking. I think nosotros volition have to leave."

Tran is one of millions of farmers around the world who is a victim of a build-up of salts in the soil, known as salinization. Where she lives close to the coast this is acquired both by poor drainage in the rice irrigation channels and by sea-level ascension, which sees saltwater overtopping the defensive dikes and inundating her state.

But she and other Ca Mau farmers now face a further trouble. Astringent droughts are becoming more than common and a serial of major dams on the Mekong have led to less freshwater reaching the delta. The upshot is more salty water penetrating further up the river estuaries and irrigation canals from the sea, devastating crops and contaminating drinking water.

salt in soil affects crops in India

Salinization is harming soils, killing crops and altering ecosystems around the world. Photograph courtesy of India H2o Portal, from Flickr, licensed under CC BY-NC-SA two.0

"Salt is a big problem," says Cong Khanahoi, vice chair of the Kanahok customs, which counts 13,000 people in nine Ca Mau villages. "The days when people could irrigate crops using the network of channels are going. In some years, saltwater reaches 100 kilometers [62 miles] inland."

Reduced Productivity

The salinization of soils is not just a threat to Vietnam, where about 500,000 acres (200,000 hectares) have been affected, co-ordinate to the Asian Development Bank. The 2018 assessment of global land degradation by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), tasked with assessing the land of the natural world, says it is 1 of the major factors reducing plant growth and productivity worldwide, affecting around twenty% of the globe'southward 740 million acres (300 million hectares) of irrigated farmland.

Soils, peculiarly in the earth'southward dry areas, are often naturally salty, simply inefficient irrigation and poor drainage atomic number 82 to waterlogging, which raises the water table, bringing salts in the subsoil nearer the surface. When the water evaporates, salt is left effectually the roots of plants, preventing them from absorbing water, stunting growth and contaminating drinking water supplies.

Salt not only degrades soils and saps crop productivity, say the IPBES authors, but increases poverty, drives economically precarious people similar Tran to the cities and undermines biodiversity.

Millions of Acres

Gauging just how much of the world'south land is affected past common salt is hard because information technology requires so many soil samples, and countries utilise different ways to measure salinity. IPBES suggests that effectually 190 million acres (76 million hectares) of mostly irrigated state has been permanently lost to salinity and can no longer exist farmed, with a further 150 million acres (sixty 1000000 hectares) damaged. Nearly ii.five billion acres (1 billion hectares) in 100 countries are afflicted to some extent, mostly naturally, it says.

The more that irrigation is used to increase food product, the more saline soils become, say researchers. The U.S. Bureau for International Development (United states AID) estimates that some 25 million acres (10 million hectares) of land are lost every year to salinization or water saturation; a United nations University Constitute for Water, Environs and Health (UNU-INWEH) study estimates that the amount of salt-affected land in barren or semi-arid regions has grown from 111 million acres to 153 million acres (45 million hectares to 62 million hectares) since the 1990s.

"Irrigation inevitably leads to the salinization of soils and waters. … In many countries irrigated agriculture has caused environmental disturbances such as waterlogging, salinization, and depletion and pollution of water supplies. Business organization is mounting almost the sustainability of irrigated agronomics," co-ordinate to a report by the U.S. Department of Agronomics. It suggests ingather yield reductions due to salinity occur on an estimated 30% of all 56 million acres of U.S. irrigated land.

Adjusted from Wicke, B., et al. The global technical and economic potential of bioenergy from table salt-affected soils. Energy Environ. Sci. 2011(iv): 2669–2681. Click to expand.

Manzoor Qadir, assistant director of the UNU H2o and Human Evolution Programme and chief author of the United nations-INWEH study, says that the worldwide almanac cost of salt-induced state degradation in irrigated areas is United states of america$27.3 billion because of lost crop production. The event is likely to be college nutrient prices and food shortages, he says.

"Salinity constitutes a real threat to the world achieving the 70% increment in food production that the UN has projected could be needed past 2050, especially in irrigated areas where large-scale salinization occurs. Irrigated areas make up about 20% of global cropland but produce about forty% of global food product. The rain-fed surface area consist of 80% of cropland but produces most sixty% of global nutrient," says Qadir.

Worst Affected

The global figure is uncertain, simply researchers agree that the worst affected regions include India'south Ganges bowl (about fifty meg acres or xx 1000000 hectares of irrigated land), China's Yellow River bowl (17 meg acres or 7 million hectares), the Indus basin in Islamic republic of pakistan (8 million acres or 3 million hectares) and the Colorado River basin in the western U.S. (xiii meg acres or five one thousand thousand hectares). Many coastal regions in Bangladesh, the Philippines, Egypt, Commonwealth of australia, Iraq and Turkey are becoming more decumbent to salt intrusion as ocean levels rising.

Salinization is not new, says Pichu Rengasamy, a soil researcher in the School of Agriculture at Adelaide University, Australia. He points out that information technology was responsible for the refuse of ancient Mesopotamian civilization 4,000 years ago.

"In our experience in Australia, only recently are farmers condign enlightened of subsoil salinity constraints to crop productivity," Rengasamy wrote in an email.

salinization in Colorado River basin

Salt problems exacerbated by human being action are altering habitat and farmland in the Colorado River basin. Photograph courtesy of NRCS/Ron Nichols

One of the worst-hit areas is the Colorado River bowl, which stretches into Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming. The river and its tributaries supply h2o to more than 38 million people and gargle more than than 7,000 square miles (18,000 square kilometers) of farmland. The salinity of the river has doubled in 60 years, by and large due to the edifice of dams, irrigation and evaporation in reservoirs, says researcher Gabriel LaHue, a graduate educatee in the Soils and Biochemistry Graduate Group at the University of California, Davis.

Costly Changes

Salinity costs farmers and states dearly. A 2010 study of Republic of iraq farming, financed by Australian and Italian governments, found farmers using only xxx% of their country for cropping and achieving merely 50% of expected yields. Bangladeshi households affected by salinity earn nearly twenty% less a year than those those with good for you soils, says Joyce Chen, a development economist at Ohio State University.

Chen says salinity acquired by rising ocean levels is likely to force about 200,000 farmers a year to drift from Bangladeshi coasts.

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"As sea levels ascent, low-lying coastal areas are increasingly beingness inundated with saltwater, gradually contaminating the soil," she says. "These salts can be prodigal by rainfall, but climate change is likewise increasing the frequency and severity of extreme weather condition events, including droughts and heat waves." The result is fifty-fifty more need for groundwater, leading to further depletion of the water table and further salinization of soils.

"People's republic of bangladesh is not unique in there existence an effect of salinity on migration, simply the mechanisms will likely differ elsewhere. In the coastal region of the U.S., contamination of soils may have less of an consequence, given the smaller role of agriculture in the economy, with alluvion gamble and damage playing a larger part," says Chen.

Spectrum of Solutions

Soil salinity can be reversed, but it takes fourth dimension and is expensive. Solutions include improving the efficiency of irrigation channels, capturing and treating salty drainage water, setting upward desalting plants, and increasing the corporeality of water that gets into aquifers. Mulches to save water can also be applied to crops.

The more loftier-tech solution is to develop genetically engineered and other salt-tolerant crops. Only the science is not straightforward and is controversial, and the result is that non many varieties are available in large quantities.

In coastal areas of many developing countries, similar People's republic of bangladesh, Vietnam and Thailand, where brackish or salty water is most common, many thousands of pocket-sized farmers have switched from rice to shrimp farming. This is lucrative, but can exist financially and ecologically risky, leading to more salinization and deforestation. The rush to shrimp farming has also led to disharmonize, with rice paddy fields being deliberately flooded in order to force farmers off their lands.

shrimp / prawn farming in the Mekong Delta

In the brackish waters of the Mekong Delta, some rice farmers take taken upward raising shrimp instead of, or in addition to, rice. Photo courtesy of Vietnam News Bureau

Irrigating crops has been important for agronomics for thousands of years, just the lesson is that unless societies learn to avert the waterlogging and salinization that so often comes with it, disaster will follow.

"Vast areas of cultivable land in the coastal areas where once rice was grown have been turned into shrimp farms because of salinization," says Mizanur Rahman, professor of soil scientific discipline at Bangabandhu Sheikh Mujibur Rahman Agricultural Academy in Bangladesh. "When monsoon rainfall comes early on and rains heavily, the shrimp producers keep on adding actress salt into the water to ensure better growth of the shrimps. The extra table salt adds to the level of soil salinity farther, making the country unusable," he says.

Irrigation has immune nutrient production to see the needs of near of the world's fast growing populations. But the heavy demand information technology makes on freshwater supplies is now straining nutrient supplies and harming biodiversity. Add in rising body of water levels and climatic change, and we can wait more than frequent and more serious water shortages. The swell challenge of the century will be to detect ways to use less h2o, to manage it improve and to grow food without turning the soil to salt.