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In the last 100 years , the demand for water around the world has grown twice as fast as the human population. Water scarcity is already a problem on every continent with agriculture posing a major threat to food security. And it is that, despite covering more than 70% of the earth’s surface, only 3% of the world’s water is suitable for drinking. Of this fresh water, 70% is locked up in glaciers and ice caps . Less than 0.01% of all fresh water in the world is available for human use in lakes, rivers and reservoirs.
A new study published in the journal Earth’s Future found that due to climate change, water scarcity for agriculture will increase on more than 80 percent of the world’s farmland by 2050 . In order to examine current and future water requirements for global agriculture and to predict whether available water levels will be sufficient in a world struggling with climate change, a team from the Chinese Academy of Sciences in Beijing analyzed maximum possible levels of rainwater and irrigation in each cultivation area; developed a new index to measure and predict water scarcity in the two main sources of agriculture: soil water that comes from precipitation or rain (the so-called “green water”) and irrigation of lakes, rivers or groundwater (called “blue water”).
80% of all farming areas worldwide will not have enough water by 2050. Crushing conclusion. Although water scarcity is already a problem on every continent on the globe, most water scarcity models have not taken into account either blue or green water.
This is the first study to apply a comprehensive index of possible water around the world and predict global scarcity of blue and green water as a result of climate change.
“As the largest user of blue and green water resources, agricultural production is facing unprecedented challenges,” explained Xingcai Liu , an expert on the relationship between hydrology and climate change at the Chinese Academy of Sciences. “This index allows an evaluation of the scarcity of agricultural water in both rainfed and irrigated farmland in a consistent manner.”
Is not sufficient
The amount of green water available for crops depends on the amount of rain an area receives and the amount of this water that is lost due to evaporation or runoff. Changing temperatures and rainfall patterns due to climate change, as well as intensive farming practices , mean that green water is unlikely to be enough to support the number of crops needed to support a growing population.
This new, more comprehensive index could help countries better assess the threats and causes of water scarcity and develop strategies to mitigate the impact of future droughts. Some practices that could increase agricultural water conservation include: mulch, which reduces evaporation from soils; no-till agriculture, which encourages water to infiltrate into the soil; contour farming, where farmers till the soil on sloping land in rows with the same elevation to prevent water runoff and soil erosion; or adjustments in planting time to better align crop growth with changes in rainfall patterns.
“In the longer term, 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 rising food demand,” Liu said.
Referencia: Xingcai Liu, Wenfeng Liu, Qiuhong Tang, Bo Liu, Yoshihide Wada, Hong Yang. Global Agricultural Water Scarcity Assessment Incorporating Blue and Green Water Availability Under Future Climate Change. Earth’s Future, 2022; 10 (4) DOI: 10.1029/2021EF002567
