Climate Change and Food Security in Arid and Semi-arid Zones

Fulu Tao

Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of

Sciences, 100101 Beijing, China. E-mail: taofl@igsnrr.ac.cn

Annual anomalies of global land-surface air temperature, 1850 to 2005, relative to the 1961 to 1990 mean, show that warming since 1979 has been 0.27°C per decade for the globe (IPCC, 2007).

Linear trend of annual temperatures

The largest negative trends in annual precipitation were observed over western Africa and the Sahel.

For precipitation, the global mean land changes are not at all linear, with an overall increase until the 1950s, a decline until the early 1990s and then a recovery

The land area with Palmer Drought Severity Index (PDSI <-3.0) have more than double since 1970s, due to precipitation decreasing and warming (Dai et al (2004)

Global Drought Disaster Frequency for the Cropland Growing Season

1949-2006

Li et al (2009)

Li et al (2009)

Probability Density Function of the Drought Disaster Frequency

Baseline

2100

Country-Specific Drought Risk Index of Cropland

Li et al (2009)

Li et al (2009)

Figure 5.1. (a) Current suitability for rain-fed crops (excluding forest ecosystems) (after Fischer et al., 2002b). SI = suitability index; (b) Ensemble mean percentage change of annual mean runoff between present (1981 to 2000) and 2100 (Nohara et al., 2006).

Globally, about 27% of the Earth’s land surface are too dry for rain-fed agriculture. Considering water availability, only about 1.8% of these dry zones are suitable for producing cereal crops under irrigation (Fischer et al., 2002b). Projected runoff increases in high latitudes and the wet tropics, and decreases in mid-latitudes and some parts of the dry tropics. Declines in water availability are projected to affect some of the areas currently suitable for rain-fed crops (e.g., in the Mediterranean

Observed Trends and Future Projections of Climate in China

Piao, et al., 2010

Change of Crop Water Demand in China during 1946-1995

Change of Soil Moisture in Cropland during 1946-1995

Change of Water Stress in Cropland during 1946-1995

ccSW ETaEToD −=

%100×= c

c

I EToETaY

80 90 100 110 120 130

50

45

40

35

30

25

20

Longitude

Lati

tude

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75

80 90 100 110 120 130

50

45

40

35

30

25

20

Longitude

Lati

tude

-10 -5 0 5 10 15 20

Climate Change in China in 2020s(2021-2030)

(OC) (OC)

80 90 100 110 120 130

50

45

40

35

30

25

20

Longitude

Lati

tude

0 300 600 900 1200150018002100

80 90 100 110 120 130

50

45

40

35

30

25

20

Longitude

Lati

tude

-100 -50 0 50 100 150 200(mm/year) (mm/year)

Primary Degradation TypeEtEdEoWtWdWoPaPwCnCsStableWaterNo data

Primary Degradation Type

Extent of Degradation0 - 5%5 - 10%10 - 25%25% - 50%> 50%StableWaterNo data

Rate of DegradationModerately decreasingSlowly decreasingNo changeSlowly increasingModerately increasingRapidly increasingStableWaterNo data

Impact of DegradationNoneLightModerateStrongExtremeStableWaterNo data

Extent

Impact

Cause

Rate

Secondary Degradation TypeEtEdEoWtWdWoPaPwCnCsStableWaterNo data

Extent of Degradation0 - 5%5 - 10%10- 25%25 - 50%> 50%StableWaterNo data

Secondary Degradation Type

Rate of DegradationSlowly decreasingNo changeSlowly increasingModerately increasingRapidly increasingStableWaterNo data

Impact of DegradationNoneLightModerateStrongExtremeStableWaterNo data

Extent

Impact

Cause

Rate

Impact of DegradationNoneLightModerateStrongExtremeStableWaterNo data

Primary Soil Degradation Type in 2020s

Extent of Degradation 00 - 5%5 - 10%10 - 25%25 - 50%> 50%StableWaterNo data

Extent Impact

Impact of DegradationNoneLightModerateStrongExtremeStableWaterNo data

Secondary Soil Degradation Type in 2020s

(°C)

Extent of Degradation00 - 5%5 - 10%10 - 25%25 - 50%> 50%StableWaterNo data

Extent Impact

Percent Reduction-28.2 - 0%0 - 20%20 - 30%30 - 50%50 - 70%> 70%WaterNo data

Percent Reduction-9.4 - 0%0 - 10%10 - 20%20 - 30%30 - 40%40 - 60.6%WaterNo data

Soil Water Holding Capacity (mm)0 - 3030 - 6060 - 9090 - 120120 - 160160 - 206Water or No data

Soil Water Capacity Reduction Factor Due to Soil Degradation

PET (mm)<= 350350 - 500500 - 650650 - 800> 800 No cropland or data

Impacts of Climate Change on Potential Evapotranspiration

(°C)

Change of PET (mm)<= -20-20 - 00 - 5050 - 100> 100 No cropland or data

Change of ET (mm) <= -30-30 - -20-20 - -10-10 - -0.5-0.5 - 00 - 5No cropland or data

Change of ET (mm) <= -20-20 - 00 - 5050 - 100>100 No cropland or data

ET (mm)<= 200200 - 400400 - 600600 - 800> 800 No cropland or data

Interactive Impacts of Climate Change and Soil Degradation on Actual Evapotranspiration

(°C)

Change of ET (mm) <= -20-20 - 00 - 2020 - 50> 50No cropland or dta

Change of soil moisture (mm) <= -20-20 - -10-10 - -5-5 - 00 - 10No cropland or data

Change of soil moisture (mm) <= -20-20 - -10-10 - -5-5 - -0.5-0.5 - 00 - 5No cropland or data

Soil moisture (mm)<= 3030 - 5050 - 7070 - 9090 - 120> 120 No cropland or data

Change of soil moisture (mm) <= -10-10 - -5-5 - 00 - 5No cropland or data

Interactive Impacts of Climate Change and Soil Degradation on Soil Moisture

(°C)

Change of soil moisture deficit (mm)<= 00 - 2020 - 4040 - 60> 60No cropland or data

Change of soil moisture deficit (mm) <= -20-20 - 00 - 2020 - 4040 - 60> 60 No cropland or data

Soil moisture deficit (mm) >= 200100 - 20050 - 10010 - 500 - 10No cropland or data

Change of soil moisture deficit (mm) <= -10-10 - 00 - 2020 - 50> 50 No cropland or data

Interactive Impacts of Climate Change and Soil Degradation on Soil Moisture Deficit

(°C)

Change of yield index (%) <= -10-10 - -5-5 - 000 - 5No cropland or data

Yield index (%)<= 3030 - 5050 - 7070 - 9090 - 100No cropland or data

Change of yield index (%)<= -10-10 - -5-5 - 000 - 5> 5 No cropland or data

Interactive Impacts of Climate Change and Soil Degradation on Yield Index

(°C)

Change of yield index (%) <= -10-10 - -5-5 - -0.5-0.5 - 00 - 5> 5 No cropland or data

Surface runoff (mm)<= 100100 - 300300 - 600600 - 900> 900 No cropland or data

Change of surface runoff (mm) <= 00 - 2020 - 40> 40No cropland or data

Change of surface runoff (mm) <= -50-50 - 00 - 5050 - 100100 - 150> 150 - 260No cropland or data

Interactive Impacts of Climate Change and Soil Degradation on Cropland Surface Runoff

(°C)

Change of surface runoff (mm)<= -50-50 - 00 - 5050 - 100100 - 150> 150 - 290No cropland or data

Suitability for Rain-fed Crop Probability of AET/PET < 0.5

1961-1990

2011-2040

2041-2070

Conclusion

In the past several decades, drought disaster frequency has increased due to precipitation decrease and climate warming.

There is higher confidence that future climate change will increase drought risk in drought-prone areas, consequently reduce agricultural production and food security.