CARBON SEQUESTRATION POTENTIAL OF AGROFORESTRY SYSTEMS IN THE WEST AFRICAN SAHEL: AN ASSESSMENT OF BIOLOGICAL AND SOCIOECONOMIC FEASIBILITY By ASAKO TAKIMOTO A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2007 1 ©2007 Asako Takimoto 2 To my parents and grandmother 3 ACKNOWLEDGMENTS I am indebted and grateful for many individuals and organizations who contributed to this study and my doctoral program. I thank my chair, Dr. P.K. Nair, for his dedication and guidance throughout this process, and my committee, Dr. Nick Comerford, Dr. Janaki Alavalapati, Dr. Tim Martin, Dr. Ted Schuur, and Dr. V.D. Nair, for their support and encouragement. I recognize and express my sincere gratitude to the individuals and their institutions that supported me during my doctoral studies: the School of Forest Resources and Conservation (Cherie Arias, Sherry Tucker, Dr. Tim White), University of Florida International Center (Debby Anderson), the Center for Tropical Conservation and Development of UF, the World Agroforestry Centre (especially Dr. Bocary Kaya), the Fulbright Program, and the Joint Japan/World Bank Graduate Scholarship Program (JJ/WBGSP). At the fieldwork in Ségou, Mali, I received tremendous support and cooperation from the farmers, field officers, and other collaborators. It was one of the most challenging times of my life, and I could not go through without them. Thank you to Nicole Demers, Bayo Mounkoro, Keita, Samake, and other officers in ICRAF Ségou office, Kayo Sakaguchi, Takako Uchida, Mr. Kiyoshi Sakai, and all the farmers in Ségou who let me use their fields for data collections and participated the survey. I have greatly benefited from my friendship with colleagues in the agroforestry lab at UF. I thank Solomon Haile, Alyson Dagang, Julie Clingerman, Sam Allen, Eddie Ellis, Brian Becker, Joyce Leptu, David Howlett, Wendy Francesconi, Subrajit Saha, Shinjiro Sato, and Masaaki Yamada, for the discussions and supports. To my precious friends who have been an integral part of the many years of this process, thank you Gogce Kayihan, Brian Daley, Elli Sugita, Mike Bannister, Jason and Karen Hupp, 4 Charlotte Skov, Chrysa Mitraki, Rania Habib, Maitreyi Mandal, Trina Hofreiter, Troy Thomas, and my fiancé, Nick Georgelis. Last but not least, I express my most profound gratitude to my mother Ayuko Takimoto, whose endless love and confidence in me made me come this far. 5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ...............................................................................................................4 LIST OF TABLES .........................................................................................................................10 LIST OF FIGURES .......................................................................................................................11 ABSTRACT ...................................................................................................................................13 CHAPTER 1 INTRODUCTION ..................................................................................................................15 Background .............................................................................................................................15 Rationale and Significance .....................................................................................................16 Research Questions and Objectives ........................................................................................17 Dissertation Overview ............................................................................................................18 2 THE WEST AFRICAN SAHEL: GENERAL LAND-USE AND AGROFORESTRY ........20 Description of the Region .......................................................................................................20 Climate ............................................................................................................................20 Vegetation ........................................................................................................................21 Soil ...................................................................................................................................22 Traditional Farming Systems and Agroforestry in the WAS .................................................24 Traditional Agroforestry Practices ..................................................................................25 Bush fallow/shifting cultivation ...............................................................................25 Parkland system ........................................................................................................25 Improved Agroforestry Practices ....................................................................................26 3 LITERATURE REVIEW: CARBON SEQUESTRATION POTENTIAL OF AGROFORESTRY SYSTEMS IN THE WEST AFRICAN SAHEL (WAS) .......................36 Overview .................................................................................................................................36 C Sequestration as a Climate-Change-Mitigation Activity .............................................36 Agroforestry for C sequestration .....................................................................................37 Methodologies for C Sequestration Measurements ................................................................39 Direct On-site Measurement ............................................................................................39 Inventory ..................................................................................................................40 Conversion and estimation .......................................................................................40 Indirect Remote Sensing Techniques ..............................................................................42 Modeling ..........................................................................................................................43 Default Values for Land/Activity Based Practices ..........................................................44 Accounting Methods ...............................................................................................................44 6 Approaches to Assessing C Sequestration Performance .................................................45 Fluxes of C and flow summation .............................................................................45 Average changes in the stocks of C .........................................................................45 Cumulative C storage ...............................................................................................46 Other accounting methods ........................................................................................46 Technical Problems and Uncertainties ............................................................................47 Biomass C Sequestration ........................................................................................................48 Studies in Various Ecoregions .........................................................................................48 Studies in West Africa .....................................................................................................48 Soil C Sequestration ...............................................................................................................50 Studies of Soil C Stock and Dynamics ............................................................................50 Soil C in the WAS ...........................................................................................................52 Socioeconomic Implications ...................................................................................................54 Economic Models ............................................................................................................54 National/global scale ................................................................................................54 Micro/site-specific scale ...........................................................................................55 Feasibility in West Africa ................................................................................................56 4 ABOVEGROUND AND BELOWGROUND CARBON STOCKS IN TRADITIONAL AND IMPROVED AGROFORESTRY SYSTEMS IN MALI, WEST AFRICA .................61 Introduction .............................................................................................................................61 Materials and Methods ...........................................................................................................62 Study Area .......................................................................................................................62 Republic of Mali .......................................................................................................63 Ségou region .............................................................................................................63 Selected Land-use Systems for Field Data Collection ....................................................64 Parkland systems ......................................................................................................64 Improved agroforestry systems ................................................................................65 Abandoned (degraded) land .....................................................................................66 Research Design ..............................................................................................................66 Data Collection ................................................................................................................67 Biomass measurement ..............................................................................................67 Soil sampling ............................................................................................................68 Carbon Stock Estimation .................................................................................................68 Biomass C stock .......................................................................................................69 Soil C stock ..............................................................................................................71 Statistical Analysis ..........................................................................................................71 Results.....................................................................................................................................72 C Stock in Biomass and Soil ...........................................................................................72 Total C Stock ...................................................................................................................72 Relationship between Biomass C and Soil C ..................................................................73 Discussion ...............................................................................................................................73 7 5 SOIL CARBON SEQUESTRATION IN DIFFERENT PARTICLE-SIZE FRACTIONS AT VARYING DEPTHS UNDER AGROFORESTRY SYSTEMS IN MALI ....................83 Introduction .............................................................................................................................83 Research Questions .................................................................................................................85 Materials and Methods ...........................................................................................................85 Research Design ..............................................................................................................86 Soil Preparation and Analyses .........................................................................................87 Soil fractionation ......................................................................................................87 C isotopic ratio (13C/12C) measurement ...................................................................88 Statistical Analysis ..........................................................................................................89 Results.....................................................................................................................................90 Soil Characteristics ..........................................................................................................90 Whole Soil C ...................................................................................................................91 C in Soil Fractions ...........................................................................................................92 Isotope Analysis of Whole Soil C ...................................................................................93 Isotope Analysis of C in Soil Fractions ...........................................................................94 Relationships of Data Sets ...............................................................................................94 Discussion ...............................................................................................................................95 6 SOCIOECONOMIC ANALYSIS OF THE CARBON SEQUESTRATION POTENTIAL OF IMPROVED AGROFORESTRY SYSTEMS IN MALI, WEST AFRICA ................................................................................................................................117 Introduction ...........................................................................................................................117 Research Questions ...............................................................................................................118 Materials and Methods .........................................................................................................119 Social Survey of Fodder Bank Farmers .........................................................................119 Local Market Survey .....................................................................................................120 Types of Analysis ..........................................................................................................121 Cost-benefit analysis (CBA) ..................................................................................121 Sensitivity analysis .................................................................................................127 Risk modeling ........................................................................................................128 Results...................................................................................................................................129 Demographic Characteristics of Target Population ......................................................129 Cost-Benefit Analysis: Best Guess Scenario of the Live Fence and the Fodder Bank .130 Sensitivity Analysis .......................................................................................................132 Risk Modeling and Simulation ......................................................................................132 Discussion .............................................................................................................................134 7 SUMMARY AND CONCLUSIONS ...................................................................................148 C Sequestration Potential ......................................................................................................148 Biophysical Potential .....................................................................................................148 Socioecomic Potential ...................................................................................................150 Conclusions ...................................................................................................................152 8 Agroforestry Adoption for C sequestration in the Study Region .........................................152 Limiting Factors ............................................................................................................152 Favorable Factors ..........................................................................................................153 Implications for Agroforestry ...............................................................................................154 Future Research ....................................................................................................................155 APPENDIX A SOCIAL SURVEY QUESTIONNAIRE FOR FODDER BANK OWNERS ......................156 B COST BENEFIT ANALYSIS (CASH FLOW) OF LIVE FENCE .....................................163 C COST BENEFIT ANALYSIS (CASH FLOW) OF FODDER BANK ................................167 LIST OF REFERENCES .............................................................................................................171 BIOGRAPHICAL SKETCH .......................................................................................................184 9 LIST OF TABLES Table page 2-1 Common tree and shrub species found throughout the West African Sahel .....................29 2-2 Main productive functions of agroforestry parklands ........................................................31 3-1 Summary of various biomass C measurement approaches used commonly in C sequestration studies ..........................................................................................................59 3-2 Aboveground time-averaged C stock in different ecosystems and agroforestry practices .............................................................................................................................60 4-1 Characteristics of the villages where the experimental plots were set up in Ségou region, Mali ........................................................................................................................76 4-2 Characteristics of the experimental plots (three plots average) for five-selected land- use systems in Ségou region, Mali .....................................................................................76 4-3 Estimated biomass C (above and below ground) stock values of each plot and three plots average of five selected land-use systems .................................................................77 4-4 Total C stock (biomass C + soil C of different depth) of five selected land-use systems. ..............................................................................................................................77 5-1 Soil profile characteristics for plots of the five land-use systems used in the study at Ségou Region, Mali .........................................................................................................101 5-2 δ13C values of whole soil and three fraction sizes from five studied land-use systems, at Ségou Region, Mali......................................................................................................102 6-1 Demographic characteristics of the target population in Ségou, Mali .............................138 6-2 Net Present Value (NPV), Benefit Cost Ratio (BCR), and Internal Rate of Return (IRR) of the live fence and the fodder bank projects in the three different scenarios (without C sale, with C sale by the ideal accounting method, and with C sale by the tonne-year accounting method) in Ségou, Mali ...............................................................138 6-3 NPV sensitivity of the live fence project and the fodder bank project to the change of an input variable in Ségou, Mali ......................................................................................139 10