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.
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▪
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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).
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Flowering is the most sensitive to high temperatures because of
impacts on pollination and pollen tube growth for upland cultivars.
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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