MSGID: 1:317/3 6274a4eb   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Water scarcity predicted to worsen in more than 80% of croplands   
   globally this century    
    Farming techniques that keep rainwater in agricultural soils could help   
   mitigate shortages in arid regions    
      
     Date:   
         May 5, 2022   
     Source:   
         American Geophysical Union   
     Summary:   
         Agricultural water scarcity is expected to increase in more than   
         80% of the world's croplands by 2050, according to a new study.   
      
      
      
   FULL STORY   
   ==========================================================================   
   Agricultural water scarcity is expected to increase in more than 80%   
   of the world's croplands by 2050, according to a new study in the AGU   
   journal Earth's Future.   
      
      
   ==========================================================================   
   The new study examines current and future water requirements for global   
   agriculture and predicts whether the water levels available, either   
   from rainwater or irrigation, will be sufficient to meet those needs   
   under climate change. To do so, the researchers developed a new index to   
   measure and predict water scarcity in agriculture's two major sources:   
   soil water that comes from rain, called green water, and irrigation from   
   rivers, lakes and groundwater, called blue water. It's the first study   
   to apply this comprehensive index worldwide and predict global blue and   
   green water scarcity as a result of climate change.   
      
   "As the largest user of both blue and green water resources, agricultural   
   production is faced with unprecedented challenges," said Xingcai Liu, an   
   associate professor at the Institute of Geographic Sciences and Natural   
   Resources Research of the Chinese Academy of Sciences and lead author of   
   the new study. "This index enables an assessment of agricultural water   
   scarcity in both rainfed and irrigated croplands in a consistent manner."   
   In the last 100 years, the demand for water worldwide has grown twice   
   as fast as the human population. Water scarcity is already an issue   
   on every continent with agriculture, presenting a major threat to food   
   security. Despite this, most water scarcity models have failed to take   
   a comprehensive look at both blue and green water.   
      
   Green water is the portion of rainwater that is available to plants in the   
   soil. A majority of precipitation ends up as green water, but it is often   
   overlooked because it is invisible in the soil and can't be extracted   
   for other uses. The amount of green water available for crops depends   
   on the how much rainfall an area receives and how much water is lost   
   due to runoff and evaporation. Farming practices, vegetation covering   
   the area, the type of soil and the slope of the terrain can also have   
   an effect. As temperatures and rainfall patterns shift under climate   
   change, and farming practices intensify to meet the needs of the growing   
   population, the green water available to crops will also likely change.   
      
   Mesfin Mekonnen, an assistant professor of Civil, Construction and   
   Environmental Engineering at the University of Alabama who was not   
   involved in the study, said the work is "very timely in underlining the   
   impact of climate on water availability on crop areas."  "What makes   
   the paper interesting is developing a water scarcity indicator taking   
   into account both blue water and green water," he said. "Most studies   
   focus on blue water resources alone, giving little consideration to the   
   green water."   
      
      
   ==========================================================================   
   The researchers find that under climate change, global agricultural   
   water scarcity will worsen in up to 84% of croplands, with a loss of   
   water supplies driving scarcity in about 60% of those croplands.   
      
   Sowing solutions Changes in available green water, due to shifting   
   precipitation patterns and evaporation caused by higher temperatures,   
   are now predicted to impact about 16% of global croplands. Adding this   
   important dimension to our understanding of water scarcity could have   
   implications for agricultural water management.   
      
   For example, Northeast China and the Sahel in Africa are predicted   
   to receive more rain, which may help alleviate agricultural water   
   scarcity. However, reduced precipitation in the midwestern U.S. and   
   northwest India may lead to increases in irrigation to support intense   
   farming.   
      
   The new index could help countries to assess the threat and causes of   
   agricultural water scarcity and develop strategies to reduce the impact   
   of future droughts.   
      
   Multiple practices help conserve agricultural water. Mulching reduces   
   evaporation from the soil, no-till farming encourages water to infiltrate   
   the ground and adjusting the timing of plantings can better align crop   
   growth with changing rainfall patterns. Additionally, contour farming,   
   where farmers till the soil on sloped land in rows with the same   
   elevation, prevents water runoff and soil erosion.   
      
   "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 growing food demand," Liu said.   
      
      
   ==========================================================================   
   Story Source: Materials provided by American_Geophysical_Union. Note:   
   Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. 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   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2022/05/220505143802.htm   
      
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