Climate change and arsenic contamination could lead to a significant decline in global rice production, by the end of the century, estimated at 39 percent. The dramatic scenario emerges from a study conducted by Stanford University researchers. (1)
Climate change and rice production
The negative impact of ongoing climate change on rice production has been studied repeatedly by the international scientific community. (2) Rice is the most widely consumed cereal and is the staple food for more than half of the global population.
Rising temperature and CO2 (carbon dioxide) in the atmosphere-two of the main phenomena associated with climate change-have opposite effects on rice crops. Increased CO2 in the atmosphere does indeed improve yields, but excessive temperature tends to overpower this effect and significantly decrease yields.
Floods-which also, like 90 percent of natural disasters, are associated with climate change-also reduce the ability of (minerals in) soils to absorb arsenic. The concentration and availability of which for plants therefore increases in correspondence.
CO2, temperature and arsenic, the deadly mix
The Stanford study differs from previous ones precisely in examining the impact of climate change on arsenic concentrations in soils. Researchers simulated in a greenhouse the climate conditions the planet will be in by 2100, according to estimates made in 2017 by the
International Panel on Climate Change
(IPCC).
Rice production (California variety Oryza sativa L., M206)-under the climatic conditions predicted for the end of the current century, as precisely simulated (3)-declined dramatically (-39%) from the current scenario. Arsenic, in particular, caused almost double the crop loss when compared with the combination of temperature and CO2 alone. Because‘once absorbed, arsenic reduces plant growth and development, reducing grain yield.’
Arsenic and chemical safety of food
The increased concentration of inorganic arsenic in rice grains is also a matter of serious concern.‘The doubling of inorganic arsenic in rice grain, at any soil arsenic concentration, with temperature increases of 5 °C, greatly increases the potential for dietary exposure‘ to the contaminant.
Arsenic, already present in a large proportion of the foods most eaten by children in the United States, causes damage to intellectual development and the nervous system, as well as some cancers (bladder, lung and skin). It occurs naturally in the soil, where it increases as a result of pesticide spills and industrial pollutants.
Marta Strinati and Dario Dongo
Notes
(1) Muehe, E.M., Wang, T., Kerl, C.F. et al. Rice production threatened by coupled stresses of climate and soil arsenic. Nature Communications (2019) https://doi.org/10.1038/s41467-019-12946-4
(2) Previous studies, on a different variety of rice, have concluded that under future climatic conditions-with a temperature of 38 °C and 850 ppmv (parts per million by volume) of CO2-will result in a yield reduction of about 16 percent. See, among others, the studies Matthews, R. B., Kropff, M. J., Horie, T. & Bachelet, D. Simulating the impact of climate change on rice production in Asia and evaluating options for adaptation. Agricul. Sys (1997). https://doi.org/10.1016/S0308-521X(95)00060-I and Shaobing Peng, Jianliang Huang, John E. Sheehy, Rebecca C. Laza, Romeo M. Visperas, Xuhua Zhong, Grace S. Centeno, Gurdev S. Khush, and Kenneth G. Cassman. Rice yields decline with higher night temperature from global warming. PNAS (2004). https://doi.org/10.1073/pnas.0403720101
(3) The simulation considered the 5°C increase in Earth’s temperature and 850 ppmv (parts per million by volume) of CO2 in the atmosphere, in addition to the increase of arsenic in soil
Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.
