Carbon sequestration sustainable farming in West African savannas

Carbon sequestration & sustainable farming in West African savannas: synergy or antagonism? G. Freschet 1, 2, R. J. Manlay 1, 2, Luc Abbadie 3, B. Barbier 4, C. Feller 5, M. Leroy 2, G. Serpantié 6, and J. -L. Chotte 1 1 2 3 4 5 6 IRD, UR 179 Seq. Bio, Montpellier, France ENGREF, Dpt FRT, Montpellier, France ENS/CNRS, UMR 7618 Bio. EMCo, Paris, France CIRAD/TERA, UMR CIRED, Ouagadougou, Burkina Faso IRD, RU 179 Seq. Bio, Antananarivo, Madagascar IRD, RU 168, Antananarivo, Madagascar 13. 07. 2006 1

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

What is sustainable farming ? n 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” n Is farming sustainable in West Africa ? Nutrient depletion in Agricultural Lands of West Africa (2002 -2004) (IFDC, 2006) (kg ha-1 y-1) 1000 km 30 -60 >60 3

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

Why sequester carbon in West African savannas ? n 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 5

Why sequester carbon in West African savannas ? n 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 n So, only win-win situations ? 6

But why so little C sequestration projects in West African savannas ? The facts 3 C sequestration projects in the pipeline: – – n CDM-EB: 0 WB-BCF: 2 GEF: 1? CBN: 0 2006 Mauritania Cape Verde Niger Senegal Gambia Guinea Bissau Mali Burkina Faso Guinea Sierra Leone Liberia Côte d’Ivoire Ghana Togo Benin n Nigeria Some reasons Uncertain economic background Recent ratification of the Kyoto Protocol C sequestration conflicts with political issues ≤ 2001 2002 2003 Year of ratification of the Kyoto Protocol in West Africa 2004 2005 Not ratified (26. 06. 2006) White dots: no Designated National Authority 7

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

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

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

1. Soil fertilization n The Saria long-term trial: carbon sequestration balance of soil fertilization in a ferric Acrisol of Burkina Faso t. CO 2 eq ha-1 40 y-1 Carbon accretion in soil (0 -40 cm layer) Sequestration balance Carbon depends on accretion inclusion requires mixed of fertilization manure-mediated GHG release kg nutrient ha-1 y-1 t. DM manure ha-1 y-1 Mineral fertilizer synthesis & transport (release of CO 2 and others) Mineral fertilizer application (release of N 2 O) Manure application (release of N 2 O) (adapted from Hien, 2002 ; Vlek et al. , 2004 ; IPCC, 2006) 11

1. Soil fertilization n 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 t. DM manure ha-1 y-1 (adapted from Hien, 2002) 12

1. Soil fertilization n 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 13

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

2. Conservation farming n 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 (t. CO 2 eq ha-1 10 y-1) Environmental benefit mostly Relative increase in maize yield No-input treatment = reference yield (abs. value = 301 kg ha-1) Carbon accretion in soil (0 -40 cm layer) Mineral fertilizer synthesis & transport Mineral fertilizer application Mucuna application (Azontondé et al. , 1998; Barthès et al. , 2004) 15

2. Conservation farming n Potential conflicts Uncertainty about the CH 4 -N 2 O 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 ? 16

3. Agroforestry n Objectives Increase the aboveground and belowground plant C pools Protect and increase the SOC pool n 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 17

3. Agroforestry n Example: natural and improved fallow as sequential agroforestry systems Natural fallow on a ferric Lixisol in Senegal: carbon accretion in the soilplant system as compared to crop controls DC (t. C ha-1) 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 DC (t. C ha-1 5 y-1) +27 Natural woody fallow Natural grass fallow +17 (recalculated from Manlay et al. 2002) Most accretion occurs in biomass Huge variations between tree species (Drechsel et al. 1991) High influence of the baseline scenario on the carbon balance of the practice 18

3. Agroforestry n 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 CH 4 -N 2 O balance of some perennial trees (inc. Leguminous such as Leucaena) Need for fire control (A/R schemes) 19

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

So… antagonism or synergy ? 1. Synergies on targets C sequestration option C accretion in soil tree biomass Agroecological positive impact n. Soil n. Wood n. Water n. Soil protection n. Root density content biodiversity availability n. Forage availability Improved OM recycling Farmer’s perception n. Crop yield in low-input systems protection n. Soil biodiversity & biodiversity temperature Scientific perception 21

So… antagonism or synergy ? 2. Antagonisms on resource mobilization C seq. option C accretion in soil tree biomass Resource needed Synthetic fertilizer Nutrient Conflict n. Climate- Improved OM recycling Light and water for land n. Crop n. Need (competition for residue as for labour light) cash income -power at harvest n. Tenurial barrier time n. Flexibility in cropping patterns n. Communal management of resources effect hazard Labour n. Need related economical risk n. Priming Crop residue Farmer’s perception n. Priming n. Tree-crop effect hazard Social issue competition for water n. Organic loss during transfers between plots Agroecological issue Scientific perception 22

A pragmatic issue : how do carbon sequestration strategies comply with eligibility criteria to the Clean Development Mechanism ? n n Eligible Agriculture, Forestry and Other Land Uses (AFOLU) activities Additionality Biophysical Economical n n n Verifiability Risk management Compliance with host country’s development strategy 23

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

Mitigation strategies n 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 kg. N and 0. 4 kg. P inhabitant-1 y-1 = 15 kg. CO 2 eq ha-1 y-1 or 8 kg. CO 2 eq inhabitant--1 y-1 Low environmental potential but high agricultural interest of recycling human wastes – kg. N ha-1 y-1 kg. P ha-1 y-1 Nitrogen and phosphorus losses in the village of Sare Yorobana (1996 -1997) Village deficit Loss in septic tank (Manlay et al. 2004 b) 25

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

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

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

Conclusion n 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! n n 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 29

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