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

1. 18th World Congress of Soil Science, 2006, Philadelphia, USA 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. Serpantié5, 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, Dpt AMIS, Ouagadougou, Burkina Faso 5 IRD, RU179 SeqBio, Antananarivo, Madagascar 13.07.2006

2. What ? Why ? How ? But ! So… C stock (tCeq) Project C accretion (storage) Baseline time This is C Seq Baseline C stock Cumulated indirect GHG emissions (tCO2eq) Project C stock Project GHG release Baseline time Baseline GHG emissions Project GHG emissions What 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)

3. What is sustainable farming ? • A broad definition (FAO, 1989): “one that, over the long term (present and future)… • 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”

4. 1000 km (kg ha-1 y-1) 30-60 >60 What is sustainable farming ? • Is farming sustainable in West Africa ? Nutrient depletion in Agricultural Lands of West Africa (2002-2004) (IFDC, 2006)

5. 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)

6. Why sequester carbon (OM) in West African savannas ? Because it is good for: • Smallholders • Above biomass • Soil fertility (SOM) • an indicator of the viability of low-input farming systems • Global society • C balance and greenhouse effect • Kyoto Protocol and CDM • So, only win-win situations ?

7. Mauritania Cape Verde Niger Senegal Mali Gambia Burkina Faso Guinea Bissau Guinea Nigeria Benin Sierra Leone Togo Côte d’Ivoire Ghana Liberia But why so few carbon sequestration projects in West African savannas ? • The facts • None CDM projects approval • 2 (or 3 ?) sequestration projects (agroforestry) in the pipeline of WB-BCF

8. 2006 Mauritania Cape Verde Niger Senegal Mali Gambia Burkina Faso Guinea Bissau Guinea Nigeria Benin Sierra Leone Togo Côte d’Ivoire Ghana Liberia But why so few C sequestration projects in West African savannas ? • Some reasons • Uncertain economic background • Recent ratification of the Kyoto Protocol  C sequestration conflicts with CDM’s eligibility criteria Year of ratification of the Kyoto Protocol in West Africa White dots: no Designated National Authority

9. But why so few 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

10. 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 • A South-North, farmer-scientist hybridization

11. 1. Soil fertilization • Objectives at the smallholder level • Increased plant productivity • nutrient and SOM recapitalization • Strategies • Mixed fertilisation: organic (manure, compost, green manure) + mineral (urea, rock phosphate)

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 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

14. 1. Soil fertilization • Potential conflicts • Organic fertilizers needed  availability and possible competition with other uses of plant biomass (forage, construction, cash) • If misconducted, fertilization can reduce soil carbon storage

15. 2. Conservation farming • Objectives • Reduce soil loss by erosion and leaching • Increased plant productivity • Strategies • No-till and direct sowing • Mulching • Cover crop

16. 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)

17. 2. Conservation farming • Potential conflicts • Weed control & equipment • Communal land management: common grazing habit conflict with cover crop • Tillage abandonment: does it question the distribution of gender roles in farming system management ? • Uncertainty about the N2O balance of no-till systems(Six et al., 2004)

18. 3. Agroforestry • Objectives • Increase soil fertility • Increase wood production • Protect soil against erosion • 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

19. 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)

20. 3. Agroforestry • Potential conflicts • Competition for resources • Sharing light and water: conflict with the need for land ? • Tenurial reform needed? Shift in balance of power between farmers, local decision-makers, and State • Need for fire control (A/R schemes) • Uncertainty about the N2O balance of some leguminous trees (Millar et al., 2004)

21. So… antagonism or synergy ?

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

23. Mitigation strategies 1. Wastes • 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)

24. Mitigation strategies 2. biofuel, especially woodfuel production 3. Avoided deforestation Carbon in crop residues is green gold: common grazing on millet fields in south Senegal 

25. Mitigation strategies 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 3. Avoided deforestation (X3 yield = 30 tCeq ha-1 y-1 avoided) Baseline: grass fallow Baseline: woody fallow Natural fallow Improved fallow 1.Fertilization 2. Conservation farming 3. Agroforestry

26. Mitigation strategies 3. Avoided deforestation: OK, but… • a CDM “bis” taking into consideration the avoided deforestation in the GHGs’ balance ? • Increase crop productivity does not necessary imply decrease in deforestation • The needs for : • a legal and efficient control of forest (protected area), associated to… • benefits for the local populations (Carret and Loyer, 2003)

27. Conclusion (1/2) • Implementing carbon AFOLU projects in West African savannas eligible to the clean development mechanism ?Training • The reality of insufficient harvest productivity and the nutrient soil depletion in Africa Recalculated from Lal (2006) for Africa: 0.5 MgC.ha-1.yr-1 stored in the soil increase grain production of 2.1 % per year. Necessity of new alternatives of OM (soil) management • Agricultural sustainability and C sequestration: synergy or antagonism ? • At the plot scale: pay attention to technical issues • At the farm and village levels: examine social barriers Need biophysic and socioeconomic research

28. Conclusion (2/2) • Enlarge environmental strategies • All mitigation possibilities and specially Wastes management • Avoids deforestation, but with benefit for the farmer • Win-win C sequestration projects (clean and labour efficient agriculture in Africa) • Needs (subsidized or not) for clear economical outputs at the smallholder level Even if difficult (synergy and antagonisms), probably no sustainable farming without a C sequestration perspective : One of the most important challenge for West African savannas

29. Thank you for your attention 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

31. But why so few C sequestration projects in West African savannas ? Eligibility criteria to the Clean Development Mechanism ? ForAgriculture, Forestry and Other Land Uses (AFOLU) activities in the 1st commitment period (2010) : • Afforestation/Reforestation (A/R) projects • Additionality • Biophysical • Economical • Verifiability • No negative impact: environmental and social • Compliance with host country’s development strategy