1Agricultural productivityand global change• Description of the problem• Plant and crop responses• Modeling the future food supply• Take-home pointsWhy is this hard?• Crop-climate relationships areexhaustively studied• But there’s more to the questionthan an individual crop’sresponses to climate• Scales of processes anddisciplines cover a huge rangeSocioeconomic and politicalfactors; conflictAgriculturalecosystem changesPlant responsesto physicalclimateHuman adaptationImpact of environmentalchange on foodproduction/availability• Climate (mean and variability)• Plant responses:– CO2 direct effects on photosynthesis, water, andnutrient demand• Agricultural ecosystem changes– Pests, disease responses to env. change– Water and land (availability and quality)– Other environmental constraints• Adaptive responses and their consequences– Pesticides, fertilizers, irrigation, crop varieties– Regulations• Socioeconomic/Political factors– Trade, subsidies, conflict, distribution networks– Culture2Adaptations• On the farm (as needed):• Use new varieties, change timing of planting, add ormake more efficient irrigation, fertilization, pest control• Research– Breeding new varieties to take advantage ofCO2, changed climate, changed growing season• Regulations and subsidies• Trade– Change patterns of production to emphasizeregions where comparative advantages exist.Factors that increasefood system vulnerability• Reliance on small number of foods or crops• Lack of efficient market or distribution system• Environmental unpredictability; extreme events• Lack of resources to adapt or take advantage ofalternativesClimate and Ag impactsSalinizationLikelySea level riseCrop damage, windthrowLikelyIntense trop cycloneincreaseLand degradation, crop yielddecrease, livestock death; fireLikelyDrought areas increaseCrop damage, erosion,waterlogging of soilV. likelyMore frequent heavy precipDecr. yield in warm regions; firedanger incr.V. likelyWarm spells, heatwavesincreaseIncr. yield in cooler env., decryield in warmer; incr. insectoutbreaksVirtuallyCertainWarmer; fewer cool days;more hot daysAgricultural impactLikelihoodPhenomenon anddirectionIPCC, Working group 2, Summary for PolicymakersEffect of CO2 on photosynthesis• Stronger on C3 than C4 plants3• Plants usewater moreefficientlyunder high CO2– Lower wateruse– Greater leafarea– LowerconductanceWater use perplant and per leafareaConductanceand leaf areaPhysiological response:contrast natural and agro-ecosystems• More efficient water use• More efficient photosynthesis• Natural ecosystems: these responsesmay be outweighed by other limitingfactors• Agricultural ecosystems: limitationsovercome by additions (of water,fertilizer, pest control, etc.)Direct effects from controlled studies(summary in Parry et al. 2004)What is a FACE experiment?• Free-Air CO2 Enrichment• Exposes natural or agricultural ecosystem tohigher levels of CO2 (with other manipulations,usually)• Document effects of CO2 on whole system4General trends from FACE expts• Plants respond positively to CO2 additions– Photosynthesis (C3), biomass, yield• Decreased stomatal conductance– increased water use efficiency• Nitrogen availability may control degree ofstimulation (for nonlegumes)• Soil biota activity stimulated• Belowground C storage - slight increase?• Quality of grain can varyFrom Kimball et al. 2002Quality of crops is affectedTerao etal., 2005Double CO2Ambient CO2• Protein contentdeclines by12%!Thanks to Travis Huxman for slide!http://hostg k 3.biolo g y.to h o ku.a c.jp/English%20P a ge/Rice fa ce.htm lQuality of crops is affectedResponse to Elevated CO20.00.20.40.60.81.01.21.4Grain ProteinContentFlour ProteinContentOptimal BreadMixing TimeThanks to Travis Huxman for figure!Kimball et al., 2000• Wheat protein drops, and optimal mixing timefor bread baking increases• Changes most dramatic if N is limiting, smallif N is abundantCurrent meanScience NewsHuman-generated Ozone Will DamageCrops, Reduce ProductionScienceDaily (Oct. 29, 2007) — A novel MIT study concludesthat increasing levels of ozone due to the growing use of fossilfuels will damage global vegetation, resulting in serious costs tothe world's economyhttp://www.sciencedaily.com/releases/2007/10/071027203000.htm5• Tropospheric ozone increases expected from25% (global) to 75% (certain regions).• O3 destroys rubisco (a key enzyme forphotosynthesis)• Expected 10%+ decline in crop productivity• Soybeans: biggest producers US, China,Argentina, BrazilOzone impacts on cropsModeling the future food supply• Scenario-based (different possible futures)• With and without direct effects of CO2• Predict cereal crops based on HADCM3 climatemodel projections• Feed into linked international socio-economic model– Account for population, purchasing power, demand, tradeetc.– Includes some adaptations (farm and regional level)• Calculate deviations from expectation (expectproduction to rise, all else equal)Parry et al. 2004With CO2 effectsWithout CO2 effectsParry et al. 20042020’s2050’s2080’sLivestock• Heat is stressful for livestock: breeding, fitness, longevity• Climate extremes particularly stressful (drought, heatwaves)• Forage quality seems regional, with compensating + and -effects under different climate change scenarios6Modeling the future food supplybasic conclusions• Slight-moderate decrease of global cereal yield– Only one scenario is slightly positive– Assumes full implementation of CO2 effects in the field• Direct effects of CO2 critical; otherwisedecreases are more like 10-20%• Increasing disparity between richer and poorernations• Similar scenarios can yield variable results: amore uncertain world?• World food supply not in danger, but regionaldisparities are amplifiedParry et al. 2004Cereals price response toclimate change(IPCC WG2 Ch 5)High prices benefit producers, but not consumersUS National Assessment, 2001US National Assessment, 20017Take-home messages• Global food production not necessarily incrisis under global change– This depends strongly on direct effects of CO2• Inequity (regional, national, international)likely to increase– Risk of food shortage will increase in some places• Unpredictability also likely to increase• Those who can adapt (i.e. those withresources) will benefit