Water scarcity is expected to worsen in more than 80% of croplands around the world this century.

According to a new study published in the AGU journal Earth's Future, agricultural water shortage is anticipated to worsen across more than 80% of the world's croplands by 2050.

The new study looks at existing and future water needs for global agriculture and anticipates whether available water sources, such as rainwater or irrigation, will be enough to meet those needs when climate change occurs. To do so, the researchers created a new index to quantify and predict water shortage in agriculture's two key sources: rain-fed soil water (green water) and irrigation water (blue water) from rivers, lakes, and groundwater. It's the first time a comprehensive index has been used to anticipate worldwide blue and green water shortages as a result of climate change.

"As a key consumer of both blue and green water resources, agricultural output faces unprecedented problems," said Xingcai Liu, an associate professor at the Chinese Academy of Sciences' Institute of Geographic Sciences and Natural Resources Research and the study's lead author."With this indicator, agricultural water shortage may be assessed consistently in both rainfed and irrigated croplands."

Water demand has increased twice as quickly as the human population during the last century. Water scarcity is already a problem in agriculture on every continent, posing a serious danger to food security. Despite this, the majority of water shortage models fail to account for both blue and green water in their studies.

The fraction of precipitation that is available to plants in the soil is known as green water. Green water makes up the majority of precipitation, but it is often disregarded because it is invisible in the soil and cannot be retrieved for other purposes. The amount of green water available for crops is determined by the amount of rainfall received and the amount of water lost through runoff and evaporation. Farming practises, vegetation cover, soil type, and slope of the terrain can all influence the outcome. The green water available to crops will likely fluctuate as temperatures and rainfall patterns shift due to climate change, and farming techniques intensify to satisfy the requirements of a growing population.

The findings are "very current in emphasising the effect of climate on crop water availability," according to Mesfin Mekonnen, an assistant professor of Civil, Construction, and Environmental Engineering at the University of Alabama who was not involved in the research.

"What interests me about the article is the development of a water scarcity indicator that considers both blue and green water," he added. "Most studies focus primarily on blue water resources, paying little attention to green water."

According to the researchers, worldwide agricultural water scarcity would deteriorate in up to 84 percent of croplands as a result of climate change, with a loss of water supply causing shortage in around 60% of those croplands.

Sowing solutions

Changes in available green water as a result of shifting precipitation patterns and increased evaporation owing to increasing temperatures are expected to affect around 16 percent of worldwide croplands. Including this crucial factor in our knowledge of water shortage may have ramifications for agricultural water management. More rain is expected in Northeast China and the Sahel region of Africa, for example, which might assist reduce agricultural water constraint. Reduced precipitation in the Midwest and Northwest India, on the other hand, may lead to more irrigation to support intensive agricultural.

The new index might aid governments in assessing the danger and causes of agricultural water shortage, as well as developing ways to mitigate future droughts.

Several strategies aid in agricultural water conservation. Mulching lowers soil evaporation, no-till farming increases water infiltration, and planting at different times can better match crop development with shifting rainfall patterns. Furthermore, contour farming, in which farmers plough the soil in rows of the same height on sloped ground, avoids water flow and soil erosion.

"In the long run, increasing irrigation infrastructure and efficiency, for example in Africa," Liu added, "would be viable methods to mitigate the effects of future climate change in the context of growing food demand."

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