Climate change exposure of agriculture within regulated groundwater basins of the southwestern United States

Authors: PARKER, LAUREN - University Of California; ZHANG, NING - University Of California, Davis; KISEKKA, ISAYA - University Of California, Davis; ABATZOGLOU, JOHN - University Of California; Elias, Emile; STEELE, CAITRIANA - New Mexico State University; Ostoja, Steven

Submitted to: Climate
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2025
Publication Date: 2/16/2025
Citation: Parker, L.E., Zhang, N., Kisekka, I., Abatzoglou, J.T., Elias, E.H., Steele, C.M., Ostoja, S.M. 2025. Climate change exposure of agriculture within regulated groundwater basins of the southwestern United States. Climate. 13(2). Article 42. https://doi.org/10.3390/cli13020042.
DOI: https://doi.org/10.3390/cli13020042

Interpretive Summary: The southwestern United States produces food, forage, and fiber, contributing to local, regional, and national economies. However, climate change is projected to alter the environment in which important agricultural commodities grow and may increase the incidence of conditions that are unfavorable for agricultural production. Moreover, the region’s water scarcity challenges add a critical dimension to understanding the potential effects of climate change on agricultural productivity. This study explores the effects of projected climate change on five economically-important crops across regulated groundwater basins in the Southwest states of California, Arizona, and New Mexico. The study shows that the exposure of these crops to potentially adverse climate conditions increases under warming, with increased exposure to extreme heat being most notable.

Technical Abstract: Agriculture is an important part of the economy of the southwestern United States (Southwest). Production of food and fiber in the Southwest is supported by irrigation, much of which is sourced from groundwater. Climate change projections suggest an increasing risk of drought and heat, which can affect water supply and demand, and will challenge the future of agricultural production in the Southwest. Also, as much of the groundwater in the Southwest is highly regulated producers may not be able to readily rely on groundwater to meet increased demand. Climate exposure for five economically-important crops – alfalfa, cotton, pecans, pistachios, and processing tomatoes – was analyzed over twelve regulated groundwater basins by quantifying changes in a suite of both crop-specific and non-specific agroclimatic indicators between contemporary (1981-2020) and future (2045-2074, SSP2-4.5) climates. Generally, the groundwater basins that are currently most exposed to impactful climate conditions remain so under future climate. The crops with the greatest increase in exposure to their respective crop-specific indicators are cotton, which may be impacted by a ~180% increase in exposure to extreme heat days above 38°C, and processing tomatoes, which may see a ~158% increase in exposure to high temperatures and reduced diurnal temperature range during flowering. These results improve understanding of the potential change in exposure to agroclimatic indicators, including crop-specific indicators, at the scale of regulated groundwater basins. This understanding provides useful information for considering the potential long-term implications of climate change on agriculture and agricultural water and can inform adaptation efforts for coupled agricultural and water security in groundwater-dependent regions. These results may also be useful for assessing the adaptive potential of water-conservation actions – some of which are outlined herein – or the suitability of other adaptation responses to the challenges that climate change will pose to agriculture.