Impacts of Climate Change on Agricultural Production

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1 Impacts of Climate Change on Agricultural Production Simon Donner Department of Geography University of British Columbia

2 ~40% of the ice-free land Ramankutty et al., 2008

3 Agriculture and climate Three key interactions: a major driver of climate change (via greenhouse gases and land use change) influenced by climate change may play a role in mitigating climate change

4 Agriculture climate change In 2005, 16% of global carbon dioxide emissions (deforestation) 57% of global methane emissions (manure, rice) 75% of global nitrous oxide emissions (fertilizers) Together, 1/3 rd of total climate impact, not including fossil fuels used in production!

5 Climate change agriculture Agriculture = humans harnessing photosynthesis CO 2 + H 2 O + Light CH 2 O + O 2 reaction rate depends on temperature key enzymes require nitrogen, also phosphorus and other nutrients the apparatus can be damaged by ozone

6 Climate change agriculture Basic biochemistry and biophysics tells us a lot: Increased CO 2 can be beneficial Crops should benefit from a longer growing season Increased temperatures will increase water stress on most crops (except maybe crops like millet that like dry conditions), especially in tropical countries Indirect climate change effects pest outbreaks, response of weeds are still uncertain

7 In general, expect uneven impacts Change in land suitability for food production by north wins? south loses Ramankutty et al., 2002

8 Developing world impacts Yield declines for the key crops (esp. S Asia) Calorie availability in 2050 decline (relative to 2000) By 2050, climate change will negate much of gains in child malnutrition US$ billion needed to offset (40% to Sub- Saharan Africa, followed by S Asia)

9 What about technology? Crop yields have increased thanks to genetics, chemical fertilizers; data seems to suggest minimal climate impact 180 U.S. average crop yield (bu/acre) Corn Wheat Soy

10 Technology vs. climate Climate impact (e.g. moisture stress) seen in the very high year-to-year variability in yield and production U.S. average CORN yield (bu/acre) 14,000 12,000 10,000 8,000 6,000 4,000 2, Standard deviation (10 yr)

11 Gray = expected distribution!

12 Large climate impacts on yield when you control for other factors 3.8% decrease overall Gray = expected distribution! 5.5% decrease overall

13 Large climate impacts on yield when you control for other factors 29 C

14 Large climate impacts on yield when you control for other factors 30 C

15 Large climate impacts on yield when you control for other factors 32 C

16 Carbon dioxide crop production Early work pointed to CO 2 fertilization of crop growth counter-acting deleterious climate impacts Parry et al. (2004)

17 Carbon dioxide crop production Early work pointed to CO 2 fertilization of crop growth counter-acting deleterious climate impacts Parry et al. (2004)

18 Battisti and Naylor (2009) Looking forward: heat stress In the tropics and sub-tropics, growing season temperatures are very likely to exceed the most extreme temperatures today ( )

19 Heat stress example 2003 European Heat Wave 30,000-50,000 died Italy: 36% drop in maize yields France: 30% decrease in maize + fodder 25% drop in fruit harvests Battisti and Naylor (2009); NOAA

20 Heat stress example 2003 European Heat Wave 30,000-50,000 died Italy: 36% drop in maize yields France: 30% decrease in maize + fodder 25% drop in fruit harvests Battisti and Naylor (2009); NOAA

21 N. American summer drought

22 N. American summer drought

23

24 Mitigation vs. Adaptation? Over 42% of this year's U.S. corn crop went to ethanol. Together with the drought, this led to lowest exports since 1980.

25 Mitigation vs. Adaptation 30 Corn exports (million metric tons) Poor mitigation choices leading to mal-adaptation? 0 USA, by far the largest exporter

26 Bulk world price, $/bushel August peak: $8.49/bushel Oct. 2 price: $7.58/bushel

27 Take-home messages Future prediction is hard Small-scale extremes, nutrient feedbacks, etc. not well incorporated in models Human factor: Will farmers adapt to observed changes or predictions? Even if people are rational, they don t have perfect information or ability to use information Uncertainty about technology

28 Take-home messages What we do know with some certainty: Lower crop yield in developing countries and subtropics; potential increases in the north But threshold responses and extremes may still occur in the north Direct CO 2 benefits likely overstated Pests and pathogens may be important Adaptation may allow us to offset some of the losses, but requires investment Other issues: pests, pathogens, land loss due to sea level rise (significant in developing world)