Potential Impacts of Climate Change on Cotton Production across the United States Cotton Belt and Evaluation of Adaptation Strategies

The United States (US) is a major producer and exporter of cotton (Gossypium hirsutum L.). The US produces about 20% of the world’s cotton and cotton production in the country is concentrated in the southern states, also known as the “Cotton Belt”. Air temperature and carbon dioxide (CO₂) concentration are important abiotic factors that control the growth and development of cotton. Global climate models (GCMs) project an increase in air temperature and CO₂ concentration, and changes in precipitation amounts and patterns in the future. Thus, cotton production across the Cotton Belt could face severe challenges due to projected warmer and drier future climatic conditions and changes in availability of irrigation water. The objective of this study was to investigate the effects of climate change on cotton production across the US Cotton Belt and develop appropriate adaptation strategies for sustaining cotton production in the future using the DSSAT CROPGRO-Cotton model.

Five sites across the Cotton Belt including Maricopa in Arizona, Lubbock and Chillicothe in Texas, Camilla in Georgia, and Lewiston-Woodville in North Carolina were selected for this study. The latest Coupled Model Intercomparison Project Phase 6 (CMIP6) climate projections of nine GCMs from 1950 to 2100 were obtained for the study sites for four Shared Socioeconomic Pathway (SSP) scenarios: SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP4-8.5. Data was categorized into four time periods: Historic (1950-2014), Near-future (2015-2040), Mid-century (2041-2070), and Late-century (2071-2100) to assess the effects of projected climate change on seed cotton yield and irrigation water requirement at the study sites. Modifications to planting date and row spacing were evaluated as potential climate adaptation strategies.

Results indicated that the simulated irrigated seed cotton yield is expected to increase within a range of 10-24% at all sites, except at arid Maricopa site, where irrigated seed cotton yield is simulated to decrease within a range of 24-60%.  While the negative effects of projected increases in already higher temperatures dominated the positive effects of CO₂ fertilization at Maricopa site, the opposite effects were found at the remaining four sites. The future irrigation requirement is expected to increase at all sites within a range of 4-30% to meet higher evapotranspiration requirements due to projected warmer and drier climates. Identified potential climate adaptation strategies differed across the study sites. For example, mid-season cotton planting in a narrow row spacing (75 cm) was found to be a promising climate adaptation strategy to improve irrigated seed cotton yield at Halfway while an early planted cotton with wide row spacing (100 cm) was found to be the most promising strategy for Maricopa. Findings from this study will be useful to US cotton producers in modifying agronomic practices conducive to cotton growth and development under projected future changes in climate.