carbon sequestration potential of agroforestry systems

184 Pages·2007·2.1 MB·English

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
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©2007 Asako Takimoto

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To my parents and grandmother

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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,
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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.

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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
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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
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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
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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

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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

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