Quantifying the impact of climate change and extreme heat on rice in the United States

Authors: LI, SANAI - Us Forest Service (FS); Fleisher, David; Barnaby, Jinyoung

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/28/2024
Publication Date: 7/11/2024
Citation: Li, S., Fleisher, D.H., Barnaby, J.Y. 2024. Quantifying the impact of climate change and extreme heat on rice in the United States. Agricultural and Forest Meteorology. 355. Article e110145. https://doi.org/10.1016/j.agrformet.2024.110145.
DOI: https://doi.org/10.1016/j.agrformet.2024.110145

Interpretive Summary: Rice is one of the world's most important crops and the U.S. is the 4th largest exporter. Production in the U.S. occurs in different locations including California Sacramento Valley, Gulf Coast, and Mississippi Delta. High heat is currently reducing rice yield and quality in most of these areas. Estimating the effects of projected climate changes among these production centers is vitally important given the importance of this crop for food security. To do this, multiple climate models were integrated with a sophisticated rice crop model that was modified to account for effects of high heat during flowering. The results showed that yields for different rice varieties are likely to decline between 17 to 44% from today's values due to temperature increases over the next 20 to 50 years. Atmospheric carbon dioxide (CO2) may reduce this impact to less than 5% for hybrid varieties, but is less effective at limiting heat stress impacts for conventional varieties which make up roughly 75% of rice production. Water use efficiency is also likely to decline due to both yield loss and higher evaporation rates. The study also found that the Gulf Coast was less sensitive to future heat stress impacts compared to the other locations. This study outlines the potential impacts of climate change and helps scientists to identify adaptation strategies, such as potential breeding and management guidelines, that can be studied to minimize climate impacts. Farmers, crop consultants, and agents involved in food security assessments will benefit from this information.

Technical Abstract: The United States is the world's 4th largest rice exporter and faces challenges associated with extreme heat and water availability. An ORYZA crop model, modified with revisions to phenology, heat stress, gas exchange, and energy balance components, was used to evaluate geospatial climate impacts on yield and water use. Data from three regional climate models (RCMs) were used to assess response of three cultivars, two conventional and one hybrid. Seasonal average surface air temperature increased from 1.9-2.4 degrees C in the 2040s, and 2.6-4.3 degree C in the 2070s for representative concentration pathways (RCP) RCP4.5 and RCP8.5 scenarios, respectively. Yield declined between 17-28% and 24-44% for the 2040s and 2070s, respectively, in response to climate change without CO2 fertility, and California and the north Mississippi Delta were the most vulnerable regions. The CO2 fertilization effect compensated for 15-37% of this decline which translated into higher yields compared to historical values along the Gulf coast. Elevated CO2 negated some of the temperature impact for the hybrid but was 2-7% and 6-12% less effective for conventional cultivars for 2040s and 2070s. Yield loss was associated with reduced spikelet fertility due to heat stress during anthesis (R2=0.59-0.98). Water use efficiency declined by 18-30% without, and 2-10% with, CO2 for 2040, and 27-48% without, and 4-8% with, CO2, for the 2070s, respectively. This model-based effort provides unique geospatial assessments regarding projected climate impacts on potential rice yield, and further indicates crop- and region-specific adaptation strategies for sustainable rice production to ensure food security for a growing population.