Page 138 - Climate Change and Food Systems

climate change and food systems: global assessments and implications for food security and trade
figure 4
Development of reported wheat and maize yields over time based on studies
published in the 1990s (A) (based on four studies)*, 2000s (B) (based on six studies)*
and 2010s (C) (based on four studies)*, expressed as (a) percentage difference from reference yield levels and (b) absolute yields for selected regions. Note that the reported yields for central Europe (Austria, Czech Republic, Hungary) are related to impacts of changed climatic variables only, whereas for northwest Europe
(United Kingdom, northwest France, BeNeLux) and southern Europe (Spain, Italy, Greece) both climate change and CO2 effects were considered. Box boundaries indicate the 25th and 75th percentiles; the line within
the box marks the median; whiskers below and above the box extend to 1.5 times the height of the box. Points are outliers that do not fall within the whiskers and asterisks are extreme outliers having values more than three times the height of the boxes
A = 1990s B = 2000s C = 2010s
i) Basci et al. (1991), Alexandrov et al. (2002), Eltzinger et al. (2003), Hermans et al. (2010)
ii) Favis-Mortlock et al. (1991), Ghaffari et al. (2002), Gibbons & Ramsden (2008), Semenov (2009), Hermans et al.
(2010), Wu et al. (2011), Supit et al. (2012).
iii) Iglesias & Minguez (1997), Kapetanaki & Rosenzweig (1997), Gianna-kopoulos et al. (2009), Supit et al. (2012),
Bocchiola et al. (2013).
1) Irrigated maize yields 2) Potential maize yields
* References to these studies are given as Figure Legends i-iii.
2.3 Recent progress
Over the last 20 years, considerable progress
has been made in using field experiments on
crop models to test a wider range of crops
and growing conditions as the foundation for
CC assessments. This progress is indicated by numerous publications on the topic; the intensity of publication has increased exponentially during the last five to seven years. An important advance in CC assessments over the last two decades has been the inclusion of elevated atmospheric carbon dioxide (CO2) routines in crop models and testing
3) Rainfed maize yields
these with open-top and free air CO2 enrichment (FACE) experimental data. While there is still some debate regarding whether the effect of elevated CO2 on cereal growth is overestimated, there are several studies showing that simulations are in
line with FACE experiments. Additional advances
in CC assessments include: modelling of a wider range of crops (e.g. grapevines); including nutrients other than nitrogen in simulation models (e.g. phosphorus uptake and response); considering
the sensitivity of crop growth and transpiration to soil salinity; and simulating ozone effects, water- logging and heat stress (Asseng et al., 2011,
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