Carbon sequestration & sustainable farming in West African savannas: synergy or antagonism?

1. Carbon sequestration & sustainable farmingin West African savannas: synergy or antagonism? G. Freschet1,2, R.J. Manlay1,2, Luc Abbadie3, B. Barbier4, C. Feller5, M. Leroy2, G. Serpantié6, and J.-L. Chotte1 1 IRD, UR179 SeqBio, Montpellier, France 2 ENGREF, Dpt FRT, Montpellier, France 3 ENS/CNRS, UMR 7618 BioEMCo, Paris, France 4 CIRAD/TERA, UMR CIRED, Ouagadougou, Burkina Faso 5 IRD, RU179 SeqBio, Antananarivo, Madagascar 6 IRD, RU168, Antananarivo, Madagascar 13.07.2006

2. What is carbon sequestration ? C stock (tCeq) This is carbon sequestration ! • It is “[…] the net balance of all greenhouse gases […] computing all emissions sources at the soil-plant-atmosphere interface, but also all the indirect fluxes” (Bernoux et al., 2005) Project C accretion (storage) Baseline time Baseline C stock Cumulated indirect GHG emissions (tCO2eq) Project C stock Project GHG release Baseline time Baseline GHG emissions Project GHG emissions

3. 1000 km (kg ha-1 y-1) 30-60 >60 What is sustainable farming ? Nutrient depletion in Agricultural Lands of West Africa (2002-2004) (IFDC, 2006) • A broad definition (FAO, 1989) : “one that, over the long term • enhances environmental quality and the resource base on which agriculture depends; • provides for basic human food and fibre needs; • is economically viable and • enhances the quality of life for farmers and society as a whole” • Is farming sustainable in West Africa ?

4. What are West African savannas ? 0-200 200-400 400-600 600-800 800-1000 1000-1200 1200-1400 (Mayaux et al., 2004; Ardoin-Bardin, 2004)

5. Whysequester carbon in West African savannas ? • Because it is good for smallholders • carbon is a multi-purpose tool, both a valuable good and means of production • an indicator of the viability of low-input farming systems • carbon is an increasingly scarce resource • largely a scientific point of view from the North Paddy fields and palm grove in south Senegal 

6. Why sequester carbon in West African savannas ? • Because it is good for global society • Farming in the WAS, the global carbon cycle and global change • Carbon sequestration within the Clean Development Mechanism (CDM): several eligibility criteria • Other mechanisms exist: WB, GEF, CCX… • Again, a scientific discourse from the North • So, only win-win situations ?

7. But why so little C sequestration projects in West African savannas ? • The facts • 3 C sequestration projects in the pipeline: • CDM-EB: 0 • WB-BCF: 2 • GEF: 1? • CBN: 0 • Some reasons • Uncertain economic background • Recent ratification of the Kyoto Protocol  C sequestration conflicts with political issues 2006 Mauritania Cape Verde Niger Senegal Mali Gambia Burkina Faso Guinea Bissau Guinea Nigeria Benin Sierra Leone Togo Côte d’Ivoire Ghana Liberia Year of ratificationof the Kyoto Protocolin West Africa White dots: no Designated National Authority

8. But why so little C sequestration projects in West African savannas ? • Working hypothesis • There are heavy biophysical and social barriers(other than weak institutional capacity)that make C sequestration in the WAS much conflict-raising and uncertain Millet harvest in manured fields south Senegal 

9. Agro-forestry Carbon pool Carbon flow Atmosphere Atmosphere fire Net primary Tree Tree Tree Tree production Fruits, wood, forage Fruits, Grain, forage Grain, forage wood, Above Above Above Above Grass Grass forage respiration ground ground ground ground biomass biomass biomass biomass senescence AG AG manure biomass biomass Litter Litter roots roots roots roots roots roots Conservation farming senescence Soil fauna exsudation and flora Fertilization Humification leaching erosion, Soil organic matter leaching Soil organic matter Soil organic matter erosion, How sequester carbon in West African savannas ? • Two major pools of the C cycle in the WAS • Three management schemes examined as major sequestration options • South-North, farmer-scientist hybridizations

10. 1. Soil fertilization • Objectives • nutrient recapitalization • SOC accretion • Increased plant productivity • Strategy • Mixed fertilisation: organic (manure, compost, green manure) + mineral (urea, rock phosphate)

11. Sequestration balance depends on inclusion ofmanure-mediated GHG release Carbon accretion requires mixed fertilization 1. Soil fertilization tCO2eq ha-1 40y-1 • The Saria long-term trial: carbon sequestration balance of soil fertilization in a ferric Acrisol of Burkina Faso kg nutrient ha-1 y-1 (adapted from Hien, 2002 ; Vlek et al., 2004 ; IPCC, 2006) tDM manure ha-1 y-1

12. 1. Soil fertilization • The Saria long-term trial: impact of soil fertilization on cereal yield in a ferric Acrisol of Burkina Faso Relative increase in sorghum yield No-input treatment = reference yield (abs. value = 335 kg ha-1) kg nutrient ha-1 y-1 (adapted from Hien, 2002) tDM manure ha-1 y-1

13. 1. Soil fertilization • Potential conflicts • Organic fertilizers needed  possible competition with others uses of plant biomass (forage, construction, cash) • Risk management: • Low-cost SOC monitoring needs homogenous practices • Variable agroecological conditions requires diversified practices • If misconducted, fertilization can reduce soil carbon storage

14. 2. Conservation farming • Objectives • Reduce soil loss by erosion and leaching • Increased plant productivity • Improve soil biological status • Strategies • No-till • Mulching • Cover crop

15. Environmental benefit mostly 2. Conservation farming • Example: carbon accretion under no tillage and cover crop on a Nitisol in Benin • Baseline: maize with shallow weeding and no synthetic fertilizer • project: maize + no tillage + Mucuna cover crop Sequestration balance (tCO2eq ha-1 10y-1) No-input treatment = reference yield (abs. value = 301 kg ha-1) Relative increase in maize yield (Azontondé et al., 1998; Barthès et al., 2004)

16. 2. Conservation farming • Potential conflicts • Uncertainty about the CH4-N2O balance of cover crops • Weed control & equipment • Communal land management: common grazing habit conflicts with cover crop • Tillage abandonment: does it question the distribution of gender roles and balance ?

17. 3. Agroforestry • Objectives • Increase the above-ground and below-ground plant C pools • Protect and increase the SOC pool • Strategies • Simultaneous: parklands, live hedges, (hedgerows), • Sequential: fallows, improved fallows • Afforestation/ reforestation: woodlots, wind breaks Live hedge (right) and rangeland (left)in Futa Djalon, Guinea

18. Most accretion occurs in biomass High influence of the baseline scenario on the carbon balance of the practice Huge variations between tree species 3. Agroforestry Natural fallow on a ferric Lixisol in Senegal: carbon accretion in the soil-plant system as compared to crop controls Improved fallow on a ferric Acrisol in Togo: variation in the SOC (0-10 cm) amount after 5 years as compared to natural fallow controls • Example: natural and improved fallow as sequential agroforestry systems DC(tC ha-1) DC(tC ha-1 5y-1) +27 +17 (Drechsel et al. 1991) (recalculated from Manlay et al. 2002)

19. 3. Agroforestry • Potential conflicts • Competition for resources • Sharing light and water: conflict with the need for land ? • Nutrients: priming effect hazard and SOC loss • Tenurial reform needed? Shift in balance of power between farmers, local decision-makers, and State • Uncertainty about the CH4-N2O balance of some perennial trees (inc. Leguminous such as Leucaena) • Need for fire control (A/R schemes)

20. Agroforestry does better than soil management options, but… Barely predictable link between sequestration efficiency and agricultural value Comparative overview: agricultural and environmental values of these case studies Relative increase in cereal yield (unitless) Annual sequestration balance (tCeq ha-1 y-1) Baseline: grass fallow Baseline: woody fallow Natural fallow Improved fallow 1.Fertilization 2. Conservation farming 3. Agroforestry

21. So… antagonism or synergy ? 1. Synergies on targets Farmer’s perception Scientific perception

22. So… antagonism or synergy ? 2. Antagonisms on resource mobilization Farmer’s perception Scientific perception Social issue Agroecological issue

23. A pragmatic issue : how do carbon sequestration strategies complywith eligibility criteriato the Clean Development Mechanism ? • Eligible Agriculture, Forestry and Other Land Uses (AFOLU) activities • Additionality • Biophysical • Economical • Verifiability • Risk management • Compliance with host country’s developmentstrategy

24. Enlarging our viewpoint: Reassessing the contributionof West African savannas to control the pool of atmospheric greenhouse gases

25. Mitigation strategies • Closing the nutrient cycle to decrease synthetic fertilizer use ? • Wastes at the village level; N and P losses in a village of Senegal • 1.9 kgN and 0.4kgP inhabitant-1y-1 = 15kgCO2eq ha-1y-1 or 8kgCO2eq inhabitant--1y-1  Low environmental potential but high agricultural interest of recycling human wastes Nitrogen and phosphorus losses in the village of Sare Yorobana (1996-1997) kgN ha-1 y-1 kgP ha-1 y-1 (Manlay et al. 2004b)

26. Mitigation strategies • Livestock management • Investing in agriculture more than in cattle? • Improving cattle nutrition • Biofuel production Carbon in crop residues is green gold: common grazing on millet fields in south Senegal 

27. Annual sequestration balance & avoided deforestation Annual sequestration balance (tCeq ha-1 y-1) (tCeq ha-1 y-1) Relative increase in cereal yield (unitless) Annual sequestration balance (tCeq ha-1 y-1) Avoided deforestation dramatically increases the environmental value of soil management intensification Mitigation strategies: including avoided deforestation in sequestration strategies Baseline: grass fallow Baseline: woody fallow Natural fallow Improved fallow 1.Fertilization 2. Conservation farming 3. Agroforestry

28. Efficiency accountancy • Efficiency in energy, land and labour resources in the West African savannas:one example from Senegal Energy use: amount of energy required for food production Land use: yield in standing biomass of cereal crops input-kJkJ-1food tDMha-1 Sare Yorobana United States Sare Yorobana European Union (FAO 2006; Manlay et al. 2004ab; Steinhart and Steinhart, in Hall and Hall 1993)

29. Conclusion • Agricultural sustainability and carbon sequestration: synergy or antagonism ? • At the plot scale: pay attention to technical issues • At the farm and village levels: examine social barriers • Still much work for science! • Implementing carbon AFOLU projects in West African savannas eligible to the clean development mechanism ? a challenging job • Enlarged environmental strategies needed • Conventional mitigation of course… • … as well as avoided deforestation (still a hot issue but…) • Subsidize (yes!) African agriculture to keep it clean and make it labour-efficient • Support a more equitable, per-capita based approach to efforts against climate change

30. Thank you for your attention Time for questions now ! Acknowledgments this work was supported by the following institutions: • Institute of Research for Development (IRD), RU 179 http://www.mpl.ird.fr/SeqBio/ • Institute of Forestry, Agricultural and Environmental Engineering (ENGREF), FRT, http://www.engref.fr • Agricultural Research Centre for International Development (CIRAD), http://www.cirad.fr • National Center for Scientific Research (CNRS), RU Biomeco, http://www.biologie.ens.fr/bioemco/ttp://www.cnrs.fr