Retaining soil moisture key to agricultural productivity in changing climate

schedule 3 minutes
Adaptation to Climate Change Water Quality & Scarcity
About 60 percent of the world’s food production depends on rainwater alone to supply and maintain soil moisture.
Date
Scientist
Dr. Lorenzo Rosa
Division
Biosphere Sciences & Engineering
Department
Global Ecology
Terraced rice fields in Vietnam. Photo by Nathan Cima courtesy of Unsplash.

Washington, DC— Water management strategies that reduce evaporation and retain water in the soil will be necessary to fight global hunger as rainfall patterns shift in a changing climate, according to new research from Carnegie’s Lorenzo Rosa and Liyin He published by PNAS Nexus.

About 60 percent of the world’s food production depends on rainwater alone to supply and maintain soil moisture.  Such farms are particularly vulnerable to variability in precipitation, which is intensifying in a warming world.

“As extreme weather events become increasingly common and more destructive, the reliability of water from rainfall is going to be less predictable,” Rosa explained. “So, we set out to understand how food production will be affected by these challenges, particularly when it comes to the many farms that depend entirely on rainfall.”

Even under current climate conditions, Rosa and He’s analysis showed that 890 million people already rely on farms for which rainfall alone is insufficient to meet crop demand. This means lower agricultural productivity and less food.  

Caption: A country by country breakdown of the number of people whose food comes from farms at which the need for water exceeds that which is supplied by rainfall alone. This is depicted under current climate conditions, 1.5 degrees Celsius of warming, and 3 degrees Celsius of warming.
Caption: A country by country breakdown of the number of people whose food comes from farms at which the need for water exceeds that which is supplied by rainfall alone. This is depicted under current climate conditions, 1.5 degrees Celsius of warming, and 3 degrees Celsius of warming.

Looking ahead, the picture gets bleaker. If climate change mitigation strategies successfully arrest warming at 1.5 degrees Celsius—the target of global efforts to reduce the amount of carbon released into the atmosphere—then such scarcity will affect 1.23 billion people each year. If we do nothing to curb carbon emissions, then 1.45 billion people will have diminished access to food due to rainwater availability falling short of agricultural needs.

“However, there is hope,” He added. “We also demonstrated that appropriate water management strategies will enable farmers to adapt to these changing  conditions and promote food security.”

Irrigation might be a solution for some of these farms, but for many it would require costly infrastructure. However, Rosa and He found that nature-based agricultural practices that increase shade and reduce runoff such as cover crops, no-till farming, mulching, and terracing could decrease the amount of water that evaporates from the soil. This would reduce the number of people whose food supply is threatened by water scarcity by more than 100 million.

Caption: Mulching on a strawberry farm. Image purchased from Shutterstock.
Caption: Mulching on a strawberry farm. Image purchased from Shutterstock.

"We hope that these water management solutions can guide policymakers, land managers, and farmers as they work together to ensure food security and promote sustainability,” Rosa said.

Rosa joined Carnegie last year as a Staff Associate—a prestigious program designed to give young scientists the freedom and independence to pursue bold and unconventional research. His overall research program aims to understand the agricultural challenges posed by climate change and to assess various ways to decrease the environmental impact of farming. His efforts have included analyses of irrigation strategies and water storage needs, as well as evaluating solutions for the carbon footprint of fertilizer production. By examining the intersection of agriculture and climate change from every angle, Rosa hopes to increase food security while improving agricultural sustainability.