If greenhouse gas emissions continue to increase, agricultural water shortages will increase in 84% of arable land from 2026 to 2050. In this figure, dark brown shades show a greater water shortage. Credit: Liu et al.

Water scarcity in agriculture is expected to increase in more than 80% of the world’s crops by 2050, according to a new study in the journal AGU The future of the Earth.

The new study examines current and future water needs for global agriculture and predicts whether available water levels, whether from rainwater or irrigation, will be sufficient to meet these needs in climate change. To do this, researchers have developed a new index to measure and forecast water scarcity in the two main sources of agriculture: rainwater, which comes from rain called green water, and irrigation from rivers, lakes and groundwater, called blue water. . This is the first study to apply this comprehensive index worldwide and predicts a global shortage of blue and green water as a result of climate change.

“As the largest consumer of both blue and green water resources, agricultural production faces unprecedented challenges,” said Xingcai Liu, an associate professor at the Institute of Geographical Sciences and Natural Resources Research of the Chinese Academy of Sciences and lead author. new study. “This index allows a consistent assessment of agricultural water shortages in both rainwater and irrigated agricultural land.

In the last 100 years, global water demand has grown twice as fast as the human population. Water scarcity is already a problem on every continent with agriculture, which poses a serious threat to food security. However, most water scarcity models have failed to comprehensively address both blue and green water.

Green water is the part of rainwater that is available to plants in the soil. Most rainfall ends up as green water, but is often neglected because it is invisible in the soil and cannot be extracted for other purposes. The amount of green water available to crops depends on how much rainfall an area receives and how much water is lost due to runoff and evaporation. Agricultural practices, the vegetation covering the area, the type of soil and the slope of the terrain can also have an impact. As temperatures and rainfall patterns change with climate change and agricultural practices intensify to meet the needs of a growing population, green water available to crops is also likely to change.

Mesfin Mekonen, an assistant professor of civil, civil and environmental engineering at the University of Alabama who was not involved in the study, said the work was “very timely to highlight the impact of climate on water availability on crops.”

“What makes the article interesting is the development of a water scarcity indicator, taking into account both blue water and green water,” he said. “Most studies focus only on blue water resources, with little attention paid to green water.

Researchers have found that global climate shortages of agricultural water will worsen in up to 84% of arable land, with water loss leading to a shortage of about 60% of those agricultural lands.

Sowing solutions

It is estimated that changes in available green water due to changing patterns of precipitation and evaporation caused by higher temperatures will affect about 16% of the world’s arable land. Adding this important dimension to our understanding of water scarcity can have implications for agricultural water management. For example, Northeast China and the Sahel in Africa are expected to receive more rain, which could help alleviate water shortages in agriculture. However, reduced rainfall in the midwestern United States and northwestern India could lead to increased irrigation in support of intensive agriculture.

The new index could help countries assess the threat and causes of water scarcity in agriculture and develop strategies to reduce the impact of future droughts.

Many practices help to protect agricultural water. Mulching reduces soil evaporation, untreated farming encourages water to penetrate the soil, and adjusting planting time can better bring crop growth in line with changing rainfall patterns. In addition, contour farming, in which farmers cultivate the soil on sloping land in rows of the same altitude, prevents water runoff and soil erosion.

“In the long run, improving irrigation infrastructure, for example in Africa, and irrigation efficiency would be effective ways to mitigate the effects of future climate change in the context of growing food demand,” Liu said.

With land grabbing comes competition for water, and local farmers are likely to lose

More information:
Xingcai Liu et al, Global Assessment of Water Scarcity in Agriculture, Including the Availability of Blue and Green Water in Future Climate Change, The future of the Earth (2022). DOI: 10.1029 / 2021EF002567

Provided by the American Geophysical Union

Quote: Forecast of worsening water scarcity in more than 80% of arable land worldwide this century (2022, 5 May), drawn on 5 May 2022 from

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