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Adaptation of Gambian
Agriculture to Climate Change:
Novel or re-discovered strategies
Prepared by the AF47 team
Momodou Njie, Molly Hellmuth, Peter Droogers, Bubu Jallow,
John Mac Callaway, Bernard Gomez
and
presented at the
Second AIACC Regional Workshop for Africa and Indian Ocean Islands
24 – 27 March 2004
Hotel Ngor Diarama, Dakar, Senegal
Relevance
pre-1970
current
distant future
0.30
probab. (%)
0.25
0.20
0.15
0.10
0.05
0.00
0
500
1000
Percentage occurrence of rainfall rainfall (mm)
< 600mm < 1000mm
pre-1970
3.0
35.7
current
9.1
90.9
future
80.8
99.5
1500
2000
Approach
• Literature review
• Collection of physical and socio-economic
data
• Qualitative assessment of coping/adaptation
strategies
• Crop modelling
• Benefit-cost and economic analyses
Some GCM results
Yundum
ECHAM4_A2
42
42
40
40
Max. Temp. (oC)
Max. Temp. (oC)
Yundum
HadCM3_A2
38
36
34
38
36
34
32
32
30
30
OBS GCM
1961- 2010- 20701990 2039 2099
OBS GCM
1961- 2010- 20701990 2039 2099
More GCM results
2000
Precipitation (mm y-1)
Precipitation (mm y-1)
2000
1600
1200
800
400
1600
1200
800
400
0
0
OBS GCM
1961- 2010- 20701990 2039 2099
Yundum
HadCM3_A2
OBS GCM
1961- 2010- 20701990 2039 2099
Yundum
ECHAM4_A2
Qualitative Assessment of Traditional Coping/Strategies
Strategy
Constraint(s)/Uncertainties
1
Crop diversification and selection 50% decrease in mean rainfall
50% increase in standard deviation
(HadCM3_A2)
2
Plot dispersal
50% decline in per capita availability
of prime land (< 5ha/dabada by
2025)
3
Sale of assets (raising cash)
40 – 50 % of dabadas possess
livestock
4
Relief
food aid trends, social support
networks
5
Shift in main food sources
Adaptation Strategies identified in The Gambia’s INC
Strategy
1
Introduction of new crops
2
Extensification of most hardy
crops
3
Development of irrigated
agriculture
4
Shifting planting dates
5
Reduction of post-harvest losses
Remarks
A re-statement of crop selection
Fundamental changes to
traditional production systems
Adaptation Strategies investigated by A47
Strategy
Rationale
1
Introduction of new crops
Expected decline in rainfall, and increased
variability
2
Soil fertilisation
Expected decrease in prime land availability,
degradation of arable land (assume 2% per
decade), and availability of land which
require some amendments (14%, second
largest class of agriculturally suitable land)
3
Irrigation
Expected changes in rainfall patterns, and
increased variability, possibility of extending
growing season and expanding cultivated
area,water availability (ground and surface
water)
Analytical Framework
Social/Political acceptability
Climate Scenarios
(SRES)
RegCM/Downscaling
Socioeconomic
Scenarios
Land &
Water
Resources
Crop Model
Crop
Production
Benefits and
Costs
Adaptation Options
Crop Modelling
Radiation
Light interception
Potential
photosynthesis
Water and/or
salt stress
Actual
photosynthesis
Maintenance
respiration
SWAP-WOFOST
Leaf area
Dry matter
increase
Partitioning
Roots
Death
(alive)
Death
Stems
(alive)
Growth
respiration
Storage organs Leaves
(alive)
(alive)
Death
Crop Modelling Results
Distant Future (2070 – 2099)
average
(kg ha-1)
No adaptation
Crop variety
Fertilizer
Irrigation
Supplemental Irr.
1069
1327
1480
1702
1250
Yield
change
(%)
+24
+38
+59
+17
CV (%)
50
34
38
10
37
Macroeconomic Analyses (1)
Stock-to-utilisation ratio = 20%
Base Case
Frequency of
crisis years
Food Aid &
Commercial
Imports
CC No Adaptation
CC + Irrigation
4/30
30/30
25/30
$60,623,069
$4,158,558,131
$357,015,844
Stock-to-utilisation ratio = 0%
Base Case
Frequency of
crisis years
Food Aid &
Commercial
Imports
CC No Adaptation
CC + Irrigation
3/30
30/30
21/30
$24,477,446
$3,965,637,162
$188,394,342
Macroeconomic Analyses (2)
STU ratio = 0 %
STU ratio = 20 % Remarks
CC damages
$3,941,159,716
$4,097,935,062 Food Aid/Import Bill
with CC and no
adaptation vis-à-vis
Base Case
Project benefits
$3,777,242,820
$3,801,542,287 Food Aid/Import Bill
with CC and
Irrigation vis-à-vis
CC and No
Adaptation
Net project
benefits
$3,739,616,047
$3,763,915,514 Project benefits less
project costs
Imposed CC
damages
$201,543,669
$334,019,546 Climate change
damages less net
project benefits
Microeconomic Analyses
Yield response for different WUEs
high WUE
500
2.0
high WUE
low WUE
B/C = 1
low WUE
400
1.5
300
B/C
yield increase (kg/ha)
1m3= $0.31
1.0
200
0.5
100
0.0
0
0
100
200
300
400
0
500
100
200
300
1m3= $0.12
1m3= $0.05
high WUE
2.0
high WUE
2.0
low WUE
low WUE
B/C = 1
1.0
1.0
0.5
0.5
0.0
0.0
200
300
Irrigation (mm)
400
B/C = 1
1.5
B/C
B/C
1.5
100
500
Irrigation (mm)
irrigation (mm)
0
400
500
0
100
200
300
Irrigation (mm)
400
500
Work to be done
• Evaluate benefits of conjunctive use of surface and
groundwater
• Develop future socio-economic scenarios
• Detailed/refined economic analyses
THANKS FOR YOUR
KIND ATTENTION