Xiong Wei — Crop yield responses to past climatic trends in china

1. Crop yield responses to past climatic trends in China Wei Xiong IEDA CAAS Email: [email protected] InstituteofEnvironmentandSustainableDevelopmentinAgriculture(IEDA)/ChineseAcademyofAgriculturalSciences(CAAS)

2. Overview Background Methods Results Summary

3. Background Previous studies deal with the impacts of future climate change (2020s, 2050s,2080s), those results can hardly be used by current adaptation activities. Yield change for different periods and Changes in total cereal production under different scenarios (a: without CO2 effects, b: with combinations of drivers (Xiong et al. Global Envion. CO2 effects) (Xiong et al, 2009) Change)

4. Background Observedwarming trendshavetriggered abundantadaptation activitiesinChina recently. Adoptionofnewcultivars Adjustmentofsowing dates Newmanagements Improvedinfrastructures Antileakageditch AgroForestsystem Sowingwithwaterinjection Plasticfilmbetweenrows

5. Background Thebasicinformationfordeployingtheadaptationresourcesislimited Currentandfutureclimaterisk Cropyieldstothatclimaticrisks Themechanisms Sensitivityandvulnerability Cropyieldsincreasedduringthepastdecades,butsignificantspatial variationexistduetodifferencein. Climatetrends Climateimpacts Cropresponses Adaptationcapacity Inordertoincreaseeffectivenessoftheadaptation,weneedtoknow thereasons Whytheimpactsaredifferent Whereandwhichcropsystemarethehottestriskspotsneedprioritizethe adaptationinvestments. Thebarriersforpossibleadaptations

6. Theresearchobjectives Theclimaticrisksfordifferentcropsystems andlocations Cropyieldresponsestotheclimatictrends Vulnerableregionstotheclimatechange Mechanismsforthevulnerabilities

7. Methods Usedobservedclimatedatafrom19812007to identifytheclimaticrisks(T,DTR,P,R,etc.) Usedcountystatisticdatafrom19812007 Applyingregressionanalysistoinvestigatethe yieldresponses,andestimatetheneteffectsof climatechange Y=aX+b,Y=a1 X1+a2 X2+..+b Usingdifferentdetrendingmethods(detrend theyields:firstdifferent,andlineardetrending) andmethodofsimulationtogaugethe uncertainties.

8. Results1:Climaticrisksforthemainfood crops Thegrowing season warmingwas significantforallcrops, with0.43,0.58,0.45 and0.45Cper10 years,respectively,for rice,wheat,maizeand soybean. Spatialdifferenceare obviousfordifferent crops.

9. Results1:Climaticrisksforthemainfood crops Changesinother climaticvariablesare pronouncedinsome areas,implying specificrisksfor differentcropsand locations.E.g. insufficientradiationforrice ineastChina Increasedextremehigh temperaturedays(>35) duringtheflowingperiodfor riceinYangtzeRiverValley DecreaseDTRformaize, wheat,andrice,butwith differentspatial characteristics.

10. Results2:Yieldresponsestothechanges oftheclimaticvariables Asameclimaticriskhascontrastimpactsondifferentcrops. e.g.ForaCgrowingseasonwarming,yieldsincreasedinNEforrice,maize,andsoybean, whiledecreaseforwheat;yieldsdecreasedinLPformaizeandsoybean.InsouthwestChina, maizeyielddecreasesubstantially,whilenotforothercrops. Estimatedyieldimpacts (%)(comparedtothe yieldaveragefrom1981 2006)bya1Cincrease inT,for(a)rice,(b)wheat, (c)maize,and(d) soybean.

11. Results2:Yieldresponsestothechanges oftheclimaticvariables Differentclimaticvariableshavedifferentimpactsofcropyields. e.g.Forwheat,pastgrowingseasonwarminganddecreaseinRdecreasedyields,butdecreasein DTRandPtendedtoincreaseyields. Estimatedwheatyield impacts(%)(comparedto theyieldaveragefrom 19812006)by(a)a1C increaseinT,(b)a1C decreaseinDTR,(c)a 10%decreaseinR,(d)a 10%decreaseinP.

12. Results3:Neteffectsofpastclimatic trends Over40%ofthefoodcroplandexhibiteddepressedyieldsduetopast climaticvariables SubstantialdecreaseinLP,WestofNortheastChina,andareasinYangtzeRiverBasin. Estimated decreases in food production due to the past climatic trends (compared to the average in 1981-2007).

13. Results4:Uncertaintiesduetousing differentmethods Usingthedifferentdetrendingmethodcancausedthedifferencein estimatedresults,cropmodeltendstounderestimatethespatial variationsoftheimpacts,andinsomewhereestimatedalessnegative impactofclimatechange. Comparison of estimated wheat yield change (%) to 1 C growing season warming via first difference vs. estimations from (a) the removal of linear time trends in yield, and (b) the CERES- Wheat simulated potential irrigated yields.

14. Results5:Themechanismsforthe vulnerability TheLoessPlateau: Warming,anddecreasedDiurnalTemperatureRange,nosignificantchangesin Precipitation,Radiation,andExtremeevents. duetothelessbetterirrigationanddrainageinfrastructures,waterstressesfor maizeandsoybeanunderthewarmingconditionscontributedtothe vulnerability. TheYangtzeRiverBasin: Lesswarmingextent,butincreasedDiurnalTemperatureRange,increased precipitation,decreasedRadiation,increasedheatevents.Yielddamagesby moreheatstresses,andinsufficientradiationonrice,andexcessmoistureon wheatledtothevulnerability. TheWestofNortheastChina: DecreasedDiurnalTemperatureRangereducedtheyieldsofspringwheat, whichresultedinthevulnerabilityinwestofnortheastChina.

15. Highlights Past climatic risks for food production: growing season warming, decreased Diurnal Temperature Range, insufficient radiation, and increased extreme events. Yield responses are differ depend on crops, locations, and adaptation capacity Maize and soybean suffer most Rice is benefited, wheat suffers in some areas Several producing regions are vulnerable The Loess Plateau West of NE Some Areas in Yangtze River Basin Adaptation investments might be prioritized in Irrigation and drainage infrastructures. Measures to deal with higher day temperatures

16. Ongoing works are still stressed on: Benefits of costs of specific adaptations Integration of adaptation measures, monitoring, infrastructures, managements, biotechnology, insurances, etc. Risk management in the context of climate change Promote the food production by adapting to the warming climate

17. THANKS

Xiong Wei — Crop yield responses to past climatic trends in china

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