Adaptation to Climate Change for Agriculture in The Gambia: An explorative study on adaptation strategies for Millet

1. Adaptation to Climate Change for Agriculture in The Gambia: An explorative study on adaptation strategies for Millet Dr. Momodou Njie Blue Gold Solutions ®, Banjul,The Gambia Bernard E. Gomez and Bubu Pateh Jallow Global Change Research Unit, Department of Water Resources, Banjul, The Gambia; Molly E. Hellmuth Columbia University, Columbia, USA John M. Callaway , UCCEE, Risoe, Denmark Peter Droogers, Future Water, The Netherlands

2. Late Millet

3. Objective of the Study • Develop and implement an analytical tool for estimating and comparing the costs and benefits of adaptation projects in the agricultural sector of the Gambia; • Make the Tool Available to the AIACC Community and other interested research groups; • Funding provided under the AIACC Project (UCCEE -RISOE/UCT/GCRU-DWR)

4. Methodology and Tools The main steps were: • Collection of base data and information; • Extraction of IPCC projections for The Gambia; • Post-processing GCM projections using downscaling of the HadCM3 and ECHAM4 outputs; • Setting up an environmental and biophysical model; • Evaluation of projected climate change impacts on yields; • Identification and selection of most appropriate adaptation strategies from the INC centered around water availability, nutrient availability, and water use efficiency ; • Economic evaluation of these adaptation strategies.

5. The Environmental and Biophysical Model This study used the coupled SWAP-WOFOST model. • SWAP (Soil-Water-Atmosphere-Plant) simulates one-dimensional water, solute, and heat transport in saturated and unsaturated soils whereas • WOFOST (the WOrld FOod STudies model) provides a detailed description of crop growth processes from emergence to maturity.

6. Impact of Climate Change on Millet Production • Simulated millet yields (Table 1) indicate an increase in average yields of 2% (1,046kg/ha ECHAM4) to 13% (1,141kg/ha HadCM3) in the Near Future • In the distance future the HadCM3 and ECHAM4 simulations suggest average yields change of – 68 (243kg/ha) to 38% (1,274kg/ha) about the reference period yield of 1,030Kg/ha

7. Identified Adaptation Strategies Using the recommendations in the Gambia’s INC (GOTG, 2003) on potential adaptation measures in the agricultural sector, and new insights from this study, the following three adaptation strategies are explored: • (i) Improved crop variety(-14 to 13% in the near future; -2 to 65% in the distance future), • (ii) Enhanced use of fertiliser(33 to 39% near future and expo. to 142% distsnt future), and • (iii) Introduction of irrigation(38 to 44% in the near future droping by 5% due to water logging beyond 200mm/yr delivery; delivery <200mm gives a 34% increase under ECHAM4; Under HadCM3 average yield increases by 214 and 412% with delivery rate of 200 and 500 mm/yr. respectively)

8. Economic evaluation of adaptation strategies • The economic analysis uses costs and benefits of adaptation strategies within a national cereal self-sufficiency/import substitution framework. • Two responses to climate change are evaluated: • Business as Usual • Adaptation using Irrigation and alternatively, Fertilisation • Benefit-cost analyses undertaken consist of subjecting the selected adaptation strategies to economic efficiency tests.

9. Economic evaluation of adaptation strategies (Cost Effectiveness Table 6) • A discount rate of 9% and a project horizon of 60 years was used. • Costs are both technology- and scale-dependent, with solar-based technology systems exhibiting the highest development cost per hectare or per cubic meter (m3) of water. • Operation and Maintenance (O&M), and distribution costs represent the two largest components. • For both surface and groundwater, and independent of scale, O&M and distribution account for 80 – 90% of total cost of irrigation using diesel-based water-lifting technologies.

10. Economic evaluation of adaptation strategies(Benefit-Cost Analysis Tables 7 & 8) • Tables 7 and 8 summarise the results of computations based on (i) irrigation; and its alternative (ii) fertilisation. • Table 7 shows negative net benefits of irrigation as an adaptation option in the near future (2010 – 2039). • The net adaptation benefits (NAB) become positive when water cost drop below 0.09USD/m3

11. Economic evaluation of adaptation strategies (Benefit-Cost Analysis Tables 7 & 8) • In contrast, irrigation in the distant future could be an economically efficient adaptation measure against climate change losses. However, such efficiency is related to policy variables like the stock-to-utilisation (STU) ratio governing import of cereals. • Imposed cost of climate change (ICCC) can also be minimised by decreasing cereal intake from 250 kg/capita to 175 kg/capita, ICCCdrops to USD704 million, but NAB become negative, at an STU of 10%. • But Increase STU and net benefit worsens and so minimisation of ICCC is not a straightforward matter.

12. Economic evaluation of adaptation strategies(Benefit-Cost Analysis Tables 7 & 8) • Compared to irrigation, fertiliser application, in Table 8, becomes more efficient adaptation option in the near future. • Adaptation benefits outweigh corresponding costs and cut CCD by 14 to 20%. • Positive NAB into the distant future also provides a strong indication of economic viability. • Fertilisation is less efficient than irrigation under the STU =10%, but it may be a more prudent approach if higher STU targets are central to food security policy.

13. Economic evaluation of adaptation strategies(Benefit-Cost Analysis Tables 7 & 8) • Combine business-as-usual (i.e., food imports) with fertilisation and irrigation of locally grown cereals. • In particular, expanding crop fertilisation in the short-run has significant advantages. It requires no technological sophistication, and promises high returns. • Adoption of irrigation may become an imperative in the distant futureif precipitation declines in conformity with the HadCM3 projections or world cereal markets become seriously affected by conditions in countries with historically surplus production

14. CONCLUSIONS OF THE STUDY • The study demonstrates that climate change impacts depend on the magnitude of global warming, and statistical moments of precipitation projected by GCM used in impact analysis studies. • Out of three adaptation strategies studied, cropland irrigation emerges as the most promising in terms of improving yields. • However, in the near future importation of food is more cost effective because of the high unit costs of irrigation development. • Relative economic performance of irrigation improves when water becomes a limiting crop production factor in the distance future (HadCM3 – distant future scenario).

15. CONCLUSIONS OF THE STUDY • It should be point out that there are some methodological limitations. • For instance, the performance of crop breeding as an adaptation strategy cannot be realistically and unambiguously assessed without reference to a specific millet cultivar. • Prediction of R&D outcomes so far into the future is not yet successfully celebrated. • Unconditional stability of market prices for cereals implied by constant prices may also require some modification, possibly through interfacing the analysis with a global trade model or finding some way of linking world market prices with national output.

16. CONCLUSIONS OF THE STUDY • All things considered, there is no single out-ranking adaptation strategy for agricultural crop production in the future. • Rather, our results indicate a combination of business as usual with fertilisation, in the near future, and irrigation in distant future, as the best way forward.

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