Rice yield could drop to 40% by 2100 due to increased arsenic contamination

Rice yield could drop to 40% by 2100 due to increased arsenic contamination 

•  Researchers predict that the rising global temperature will cause rice yield to drop to 40% by 2100 due to increased arsenic contamination.
• The study found that as temperatures rise, the soil of flooded paddies where rice is grown releases greater amounts of arsenic, which is then absorbed by the growing rice.
•  If the temperature rises by the estimated 5 degrees Celsius, 2 billion people who depend on rice for nutrients would no longer have access to the grain.
•  Scientists behind the study say they are “optimistic” that their research will allow communities to develop rice that adapts to the planet’s warming temperature.
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All rice contains some level of arsenic

The climate is warming, causing researchers to investigate temperature’s impact on a grain that makes its way onto almost every household’s dining room table around the world: rice. There is already evidence of arsenic contaminating rice products, but researchers at Stanford University found that the contamination could lead to a drop of 40% in rice yield by 2100 if the temperature continues to rise at its current rate.

Rice is often grown in flooded fields called paddies. As the paddies flood, arsenic, which is naturally found in most soil and sediment, is loosened into the water and absorb by the roots of growing rice plants. As global temperatures rise, the soil containing the arsenic is predicted to change, causing arsenic to absorb easier into the already sensitive rice paddies. If the temperature rises by 5 degrees Celsius by the year 2100, rice could contain twice as much toxic arsenic as it does today.

Plants that have absorbed arsenic have decreased growth and are unable to produce the same amount of nutrients. If arsenic levels in rice double, researchers predict that rice production will drop causing a significant amount of the population to no longer have access to the grain.

"By the time we get to 2100, we're estimated to have approximately 10 billion people, so that would mean we have 5 billion people dependent on rice, and 2 billion who would not have access to the calories they would normally need," said co-author Scott Fendorf, the Terry Huffington Professor in Earth system science at Stanford University's School of Earth, Energy & Environmental Sciences. "We have to be aware of these challenges that are coming so we can be ready to adapt."

As rice paddies flood, arsenic in the soil rises into the water and is absorbed by the rice

 In order to prepare for these challenges, researchers conducted an experiment in the rice-growing region of California. Using a greenhouse, which allowed them to control for temperature, carbon dioxide concentration and arsenic levels in the soil, the researchers grew a variety of medium-grain rice. They discovered that microorganisms found in soil destabilize more of the arsenic in increased temperatures, which, as predicted led to greater amounts of toxins in the water the rice adsorbed.

Most foods contain arsenic, which is why researchers aren’t as concerned about its presence as they are the level of contamination. In large quantities it can cause skin lesions, cancer, aggravation of lung disease, and in some cases, death.

While the outcome of the experiment may seem like a cause for alarm, the researchers take a more optimistic approach.

"The good news is that given past advances in terms of the global community's ability to breed varieties that can adapt to new conditions, along with revisions to soil management, I'm optimistic we can get around the problems observed in our study," Fendorf said. "I'm also optimistic that as we continue to shine a light on the threats resulting from a 5 degree Celsius change, society will adopt practices to ensure we never reach that degree of warming."