Vulnerability assessment of Southwestern crops to climate change
Vulnerability assessment of Southwestern crops to climate change Emile Elias, Caiti Steele, Albert Rango and Kris Havstad Vulnerability: Exposure, sensitivity and adaptive capacity Source: http://climwatadapt.eu/vulnerabilityindicators Previous assessments ▪ Southwestern agriculture is defined by water availability. ▪ ▪ ▪ ▪ Agriculture uses 79% of water withdrawals in the region Reduction of water demand is important for adaptation Agriculture to urban water transfers likely Irrigators could better adapt by using information already available ▪ Elevated temperatures are associated with reduced yields in some crops. Failure of some crops may occur at elevated temperatures. Crops grown in some areas might not be viable under future climatic conditions, but other crops could likely replace them. ▪ Under warmer winter temperatures, some pests persist year-round and new pests and diseases may become established. ▪ Many costs of climate change will be adjustment costs, such as relocating processing and handling facilities or irrigation infrastructure. Source: Assessment of Climate Change in the Southwest: Agriculture and Ranching Climate Change Vulnerability Assessment of Southwestern Agricultural and Forest Systems ▪ Summary of projected changes ▪ Crops ▪ Perennial specialty crops ▪ Annual specialty crops ▪ Field crops ▪ Rangelands and animal agriculture ▪ Southwestern forests ▪ Hawaii ▪ USDA programs dealing with risks and vulnerabilities ▪ GHG emissions profile and mitigation opportunities Agricultural and crop sales by county Source: Assessment of climate change in the Southwest Source: National Agricultural Statistics Service, 2012 Production value of selected southwestern crops, 2012 Field Crops Hay and Haylage: 3,155,000 acres Cotton:605,300 acres Rice: 557,000 acres Small grains: 953,000 acres Corn:924,000 acres Safflower: 75,000 acres Source: National Agricultural Statistics Service, 2012 Exposure: elevated temperatures MACA variables: Daily temperature Daily relative and specific humidity Precipitation Shortwave radiation Wind speed and direction Source: Multivariate Adaptive Constructed Analogs (MACA) http://maca.northwestknowledge.net/ Exposure: changes in precipitation Source: Multivariate Adaptive Constructed Analogs (MACA) http://maca.northwestknowledge.net/ Groundwater irrigation and surface water infrastructure in the Southwest Source: Cadillac Desert: the American West and its disappearing water By Marc Reisner Farms with diminished crops yields from irrigation interruption, 2013 ARIZONA, 2013 CALIFORNIA, 2013 NEW MEXICO, 2013 NEVADA, 2013 Source: Farm and Ranch Irrigation Survey, 2013 UTAH, 2013 Discontinuance of all irrigation by reason, 2013 Cotton in the Southwest Cotton, acres harvested Total irrigation water use by county, mgd New Mexico, 40,300 Arizona, 200,000 California, 365,000 Change in cotton production 1940 to present 900 lbs/acre-ft 635 lbs/acre-ft 335 lbs/acre-ft 978 lbs/acre-ft Impact of heat stress on cotton ▪ Reduction in fruit retention ▪ Reduce overall lint yields ▪ Delay crop maturity ▪ Reduce lint quality ▪ Sensitivity ▪ Air temperature ▪ Humidity Fruit retention in greenhouse experiments ▪ Severe heat stress damages young squares ~15 days from flowering. Flowering happens, but there are abnormalities and bolls abort 3-5 days after bloom. ▪ Problems when CANOPY is 82 to 86 ˚F (28-30˚C). Canopy temperatures in AZ are consistently 7-14˚F (4-8˚C) cooler than air temperature. Source: Cotton Heat Stress, Arizona Cooperative Extension Canopy-air temperature differential as a function of vapor pressure deficit, Yuma Valley, June Cotton sensitivity to heat and water stress Thermal Sensitivity Water stress ▪ Leaf area can decline above mean temperatures of 35°C (95°F). ▪ All southwestern cotton is irrigated ▪ Shoot biomass decreases at 30°C (86°F). ▪ Flowering is the most sensitive to high temperatures because of impacts on pollination and pollen tube growth for upland cultivars. ▪ Elevated daytime temperatures decrease photosynthesis and carbohydrate production (Bibi et al. 2008). ▪ Elevated night temperatures increase respiration and decrease carbohydrates. Temperatures higher than 30°C/20°C (86°F/68°F) day/night temperature regime caused lower boll retention in controlled environment studies (Reddy et al. 1991). Note: canopy temperatures can be much lower than ambient air temperature. ▪ Elevations of 1°C (1.8°F) in daily maximum and minimum temperature caused a decline in seed number, which is an important basic component of cotton yield (Pettigrew 2008). ▪ Heat adapted upland cotton cultivars had higher yields and heat resistance than advanced Pima cultivars (Lu et al. 1997) ▪ Drought stress can decrease leaf area, cotton yield and fiber quality. ▪ Current thought is that increased humidity of the summer monsoon inhibits cooling and lowers transpiration rates leading to higher canopy temperatures. Cotton sensitivity: temperature and interannual variability Days with heat stress for selected Arizona production areas Number of days with heat stress shows yearly variation Years with few stress days had sporadic or delayed monsoon Adaptive capacity ▪ Extension of growing season provides more flexibility in planting. ▪ Early planting and two crops per year may be planted in more areas. ▪ Cotton can be grown further north. A study reports simulated increases in cotton yield at high latitudes due to longer growing season and decreases at lower latitudes due to temperature and drought stress (Richardson et al. 2002). ▪ Need increased thermal and drought tolerance in commercial cultivars of cotton, likely drawing from foreign cultivars (Snider et al. 2011) or wild cotton strains (Bibi et al. 2010). ▪ Improve irrigation efficiency (sprinkler (12 %), gravity (84% AZ & 73% CA), low flow (5% AZ and 13% CA) Exposure: Spatial Current conditions Timeframe RCP Time of year Interannual variability Surface water Sensitivity: To increased temperature and humidity; to water scarcity Planting date and harvest date Mid-April Mid-May Early June Oct or November More reliance on groundwater Low water requirement High water requirement Mid June to mid August Low water requirement http://cals.arizona.edu/azmet/cotton.htm How can we build a more adaptive and resilient system? ▪ Think long term and short term. What could be done in a good year to prepare for a bad year? What institutional measures could we establish now to prepare for mid-century? ▪ Consider both crop and systemic vulnerabilities and adaptive capacities ▪ Adjust planting and harvest dates ▪ Irrigate at important times. Build a water information system to facilitate decision-making on a year-to-year basis. Increase water sharing capacity. ▪ Build interannual variability into spatial analysis of system ▪ Be flexible in thinking and management
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