The Chinese Academy of Agricultural Sciences (CAAS) and the International Food Policy Research Institute (IFPRI) jointly hosted the International Conference on Climate Change and Food Security (ICCCFS) November 6-8, 2011 in Beijing, China. This conference provided a forum for leading international scientists and young researchers to present their latest research findings, exchange their research ideas, and share their experiences in the field of climate change and food security. The event included technical sessions, poster sessions, and social events. The conference results and recommendations were presented at the global climate talks in Durban, South Africa during an official side event on December 1.

1. Crop yield responses to past climatic
trends in China
Wei Xiong
IEDA CAAS
Email: xiongw@ami.ac.cn
中国农业科学院 农业环境与可持续发展研究所
Institute of Environment and Sustainable Development in Agriculture (IEDA) /Chinese Academy of Agricultural Sciences (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
• Observed warming
trends have triggered
abundant adaptation
activities in China
recently.
– Adoption of new cultivars
– Adjustment of sowing
dates
– New managements
– Improved infrastructures
Anti‐leakage ditch Agro‐Forest system Sowing with water injection Plastic film between rows

5. Background
• The basic information for deploying the adaptation resources is limited
– Current and future climate risk
– Crop yields to that climatic risks
– The mechanisms
– Sensitivity and vulnerability
• Crop yields increased during the past decades, but significant spatial
variation exist due to difference in.
– Climate trends
– Climate impacts
– Crop responses
– Adaptation capacity
• In order to increase effectiveness of the adaptation, we need to know
the reasons
– Why the impacts are different
– Where and which crop system are the hottest risk spots need prioritize the
adaptation investments.
– The barriers for possible adaptations

6. The research objectives
• The climatic risks for different crop systems
and locations
• Crop yield responses to the climatic trends
• Vulnerable regions to the climate change
• Mechanisms for the vulnerabilities

7. Methods
• Used observed climate data from 1981‐2007 to
identify the climatic risks (T, DTR, P, R, etc.)
• Used county statistic data from 1981‐2007
• Applying regression analysis to investigate the
yield responses, and estimate the net effects of
climate change
△Y=a △X + b, △Y=a1 △X 1+ a2 △X 2 + ….. + b
• Using different de‐trending methods (de‐trend
the yields: first‐different, and linear de‐trending)
and method of simulation to gauge the
uncertainties.

8. Results1: Climatic risks for the main food
crops
• The growing‐ season
warming was
significant for all crops,
with 0.43, 0.58, 0.45
and 0.45 ºC per 10
years, respectively, for
rice, wheat, maize and
soybean.
• Spatial difference are
obvious for different
crops.

9. Results1: Climatic risks for the main food
crops
• Changes in other
climatic variables are
pronounced in some
areas, implying
specific risks for
different crops and
locations. E.g.
– insufficient radiation for rice
in east China
– Increased extreme high
temperature days (>35)
during the flowing period for
rice in Yangtze River Valley
– Decrease DTR for maize,
wheat, and rice, but with
different spatial
characteristics.

10. Results2: Yield responses to the changes
of the climatic variables
• A same climatic risk has contrast impacts on different crops.
e.g. For a ºC growing‐season warming, yields increased in NE for rice, maize, and soybean,
while decrease for wheat; yields decreased in LP for maize and soybean. In southwest China,
maize yield decrease substantially, while not for other crops.
Estimated yield impacts
(%) (compared to the
yield average from 1981–
2006) by a 1 ºC increase
in T, for (a) rice, (b) wheat,
(c) maize, and (d)
soybean.

11. Results2: Yield responses to the changes
of the climatic variables
• Different climatic variables have different impacts of crop yields.
• e.g. For wheat, past growing‐season warming and decrease in R decreased yields, but decrease in
DTR and P tended to increase yields.
Estimated wheat yield
impacts (%) (compared to
the yield average from
1981–2006) by (a) a 1 ºC
increase in T, (b) a 1 ºC
decrease in DTR, (c) a
10% decrease in R, (d) a
10% decrease in P.

12. Results3: Net effects of past climatic
trends
• Over 40% of the food crop land exhibited depressed yields due to past
climatic variables
Substantial decrease in LP, West of Northeast China, and areas in Yangtze River Basin.
Estimated decreases in food production due to the past climatic trends
(compared to the average in 1981-2007).

13. Results4: Uncertainties due to using
different methods
• Using the different de‐trending method can caused the difference in
estimated results, crop model tends to underestimate the spatial
variations of the impacts, and in somewhere estimated a less negative
impact of climate change.
Comparison of estimated wheat yield change (%) to 1 ºC 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: The mechanisms for the
vulnerability
• The Loess Plateau:
Warming, and decreased Diurnal Temperature Range, no significant changes in
Precipitation, Radiation, and Extreme events.
due to the less better irrigation and drainage infrastructures, water stresses for
maize and soybean under the warming conditions contributed to the
vulnerability.
• The Yangtze River Basin:
Less warming extent, but increased Diurnal Temperature Range, increased
precipitation, decreased Radiation, increased heat events. Yield damages by
more heat stresses, and insufficient radiation on rice, and excess moisture on
wheat led to the vulnerability.
• The West of Northeast China:
Decreased Diurnal Temperature Range reduced the yields of spring wheat,
which resulted in the vulnerability in west of northeast China.

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