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Farmer Livelihood Strategies and Attitudes in Response to Climate Change in Agroforestry Systems in Kedougou, Senegal

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Abstract

Farmers managing agroecological systems across sub-humid West Africa face a variety of challenges in meeting their needs. In the face of adverse conditions, farmers have successfully managed agroforestry parklands to create an ecological equilibrium. However, climate change presents a challenging and new disturbance to farmer livelihood strategies. Using a qualitative approach and a rural livelihood framework, we analyzed and assessed farmer livelihood strategies, attitudes, and responses to climate change. Results showed that farmers are constantly changing management strategies through flexible and adaptable decision-making to mitigate negative disturbances, but climate change as a primary driver to change cannot be distinguished from other normal challenges that farmers face inter- and intra-annually. Through the accumulation of knowledge and adaptive management, farmers in Kedougou derive a variety of livelihood strategies to reduce risk in the face of uncertainty and variable climatic conditions. Furthermore, farmers used trees on farms to derive a multitude of ecosystem services provided not only provisioning services such as fuel, food, and fiber, but increased biodiversity, nutrient cycling, and climate regulation. Additional research is still needed to understand to what extent the inclusion of trees on farms affect various biophysical properties as well as rationale behind species choice.

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References

  • Agyeman VK, Marfo KA, Kasanga KR, Danso E, Asare AB, Yeboah OM, Agyeman F (2003) Revising the taungya plantation system: new revenue-sharing proposals from Ghana. Unasylva 212:54

    Google Scholar 

  • ANSD (2015) Situation economique et sociale regionale: Kedougou 2013. ANSD, Ministere de l’Economie, des Finances et du Plan. Dakar, Senegal

  • Arbuckle JG, Morton LW, Hobbs J (2015) Understanding farmer perspectives on climate change adaptation and mitigation: the roles of trust in sources of climate information, climate change beliefs, and perceived risk. Environ Behav 47(2):205–234. https://doi.org/10.1177/0013916513503832

    Article  Google Scholar 

  • Assé R, Lassoie JP (2011) Household decision-making in agroforestry parklands of Sudano-Sahelian Mali. Agrofor Syst 82(3):247–261. https://doi.org/10.1007/s10457-011-9395-2

    Article  Google Scholar 

  • Badini O, Dioni L (2004) Landscape and soil characterisitcs of Madiama commune. In: Moore K (ed) Conflict, social capital and managing natural resources: a West African case study. CABI Publishing, Cambridge, MA

  • Baker K (2000) Indigenous land management in West Africa: an environmental balancing act. Oxford University Press, Oxford UK; New York

  • Bayala J, Sanou J, Teklehaimanot Z, Kalinganire A, Ouédraogo SJ (2014) Parklands for buffering climate risk and sustaining agricultural production in the Sahel of West Africa. Curr Opin Environ Sustain 6(1):28–34. https://doi.org/10.1016/j.cosust.2013.10.004

    Article  Google Scholar 

  • Bebbington A (1999) Capitals and capabilities: a framework for analyzing peasant viability, rural livelihoods and poverty. World Dev 27(12):2021–2044. https://doi.org/10.1016/S0305-750X(99)00104-7

    Article  Google Scholar 

  • Begon M, Harper JL, Townsend CR (1990) Ecology: individuals, populations, and communities. Blackwell Scientific Publications

  • Berkes F, Colding J, Folke C (2003) Introduction. In: Navigating social–ecological systems: building resilience for complexity and change. Cambridge University Press, UK, New York. https://doi.org/10.1017/CBO9780511541957

  • Berkes F, Folke C (1998) Linking social and ecological systems for resilience and sustainability. In: Berkes F, Folke C, Colding J (eds) Linking social and ecological systems: management practices of social mechanism for building resilience. Cambridge University Press, Cambridge, UK pp 1–26

  • Boffa JM (1999) Agroforestry parklands in sub-Saharan Africa. In: FAO conservation guide, vol 34, FAO, Rome

  • Brandt M, Rasmussen K, Hiernaux P, Herrmann S, Tucker CJ, Tong X, Tian F, Mertz O, Kergoat L, Mbow C, David JL, Melocik KA, Dendoncker M, Vincke C, Fensholt R (2018) Reduction of tree cover in West African woodlands and promotion in semi-arid farmlands. Nat Geosci. https://doi.org/10.1038/s41561-018-0092-x

  • Brookfield HC (2001) Exploring agrodiversity. Columbia University Press, New York

  • Bryan E, Ringler C, Okoba B, Roncoli C, Silvestri S, Herrero M (2013) Adapting agriculture to climate change in Kenya: Household strategies and determinants. J Environ Manag 114:26–35. https://doi.org/10.1016/j.jenvman.2012.10.036

    Article  Google Scholar 

  • Buotte PC, Berner LT, Hudiburg TW, Kent JJ, Harmon ME, Law BE (2018) Land use strategies to mitigate climate change in carbon dense temperate forests. Proc Natl Acad Sci 115(14), 3663–3668. https://doi.org/10.1073/pnas.1720064115

  • Burnham M, Ma Z (2016) Linking smallholder farmer climate change adaptation decisions to development. Clim Dev 8(4):289–311. https://doi.org/10.1080/17565529.2015.1067180

    Article  Google Scholar 

  • Chen C, Liu W, Jiang X, Wu J (2017) Effects of rubber-based agroforestry systems on soil aggregation and associated soil organic carbon: implications for land use. Geoderma 299:13–24. https://doi.org/10.1016/j.geoderma.2017.03.021

    Article  CAS  Google Scholar 

  • Chuku CA, Okoye C (2009) Increasing resilience and reducing vulnerability in sub-Saharan African agriculture: strategies for risk coping and management. African. J Agircultural Res 4(13):1524–1535

    Google Scholar 

  • Cook I (1997) Participant observation. In: Flowerdew R, Martin D (eds) Methods in human geography: a guide for students doing research projects. Addison Wesley Longman Limited, New York, pp 127–150

  • Crang M (1997) Chapter 11−Analyzing qualitative materials. In: Flowerdew R, Martin D (eds) Methods in human geography: a guide for students doing research projects. Addison Wesley Longman Limited, Harlow, Essex, England. pp 183–196

  • Dansokho M, Lo MM, Diop M (2012) L’évaluation économique des services des écosystèmes forestiers au Sénégal: etude de cas des communautes rurales de Niakhene et de Bandafassi

  • Davies KK, Fisher KT, Dickson ME, Thrush SF, Heron RL (2015) Improving ecosystem service frameworks to address wicked problems. Ecol Soc 20(2):37

    Article  Google Scholar 

  • Dawoe EK, Quashie-sam J, Isaac ME, Oppong SK (2012) Exploring farmers’ local knowledge and perceptions of soil fertility and management in the Ashanti Region of Ghana. Geoderma 179–180:96–103. https://doi.org/10.1016/j.geoderma.2012.02.015

    Article  Google Scholar 

  • Diedhiou B (2004) Etude de la contribution des fruitiers forestiers a la securite alimentaire

  • Diop M (2014) Summary. USAID Kedougou Synergy Meeting

  • Duvall CS (2006) Villages, vegetation, bedrock, and chimpanzees: human and non-human sources of ecosystem structure in southwestern Mali. University of Wisconsin-Madison, Madison, WI

  • Elmqvist B, Olsson L (2006) Livelihood diversification: continuity and change in the Sahel. GeoJournal 67:167–180. https://doi.org/10.1007/s10708-007-9043-6

    Article  Google Scholar 

  • Etongo D, Djenontin INS, Kanninen M, Fobissie K, Korhonen-Kurki K, Djoudi H (2015) Land tenure, asset heterogeneity and deforestation in Southern Burkina Faso. For Policy Econ 61:51–58. https://doi.org/10.1016/j.forpol.2015.08.006

    Article  Google Scholar 

  • FAO, CSE (2007) Caractérisation des systèmes de production agricoles au Sénégal: document de synthèse

  • Faye MD, Weber JC, Mounkoro B, Dakouo J-M (2010) Contribution of parkland trees to farmers’ livelihoods: a case study from Mali. Dev Pract 20(3):428–434. https://doi.org/10.1080/09614521003710013

    Article  Google Scholar 

  • Foley JA, Barford C, Coe MT, Gibbs HK, Helkowski JH, Holloway T, Howard EA, Kucharik CJ, Monfreda C, Patz JA, Ramankutty N, DeFries R, Asner GP, Bonan G, Carpenter SR, Chapin FS, Daily GC, Prentice IC, Snyder PK (2005) Global consequences of land use. Science 309(5734):570–574

    Article  CAS  Google Scholar 

  • Fosu-Mensah BY, Vlek PLG, MacCarthy DS (2012) Farmers’ perception and adaptation to climate change: a case study of Sekyedumase district in Ghana. Environ Dev Sustain 14(4):495–505. https://doi.org/10.1007/s10668-012-9339-7

    Article  Google Scholar 

  • Freitas H, Oliveira M, Jenkins M, Popjoy O (1998) The focus group, a qualitative research method: reviewing the theory, an dproviding guildines to its planning. WP ISRC 010298:1–22. https://doi.org/10.1016/j.watres.2013.02.032

    Article  CAS  Google Scholar 

  • Griscom BW, Adams J, Ellis PW, Houghton RA, Lomax G, Miteva DA, Schlesinger WH, Shoch D, Siikamaki JV, Smith P, Woodbury P, Zganjar C, Blackman A, Compari J, Conant RT, Delgado C, Elias P, Gopalakrishna T, Hamsik MR, … Fargione J (2017) Natural climate solutions. Proc Natl Acad Sci 114(44), 11645–11650. https://doi.org/10.1073/pnas.1710465114

  • Gruber JS (2010) Key principles of community-based natural resource management: a synthesis and interpretation of identified effective approaches for managing the commons. Environ Manag 45(1):52–66. https://doi.org/10.1007/s00267-008-9235-y

    Article  Google Scholar 

  • Hansen HH, Sanou L, Nacoulma BMI (2008) Tree leaves in the diet of free-ranging ruminants in three areas of Burkina Faso. Livest Res Rural Dev 20(3):1–9

    Google Scholar 

  • IPCC (2012) Managing the risks of extreme events and disasters to advance climate change adaptation. In: Field CB, Barros V, Stocker TF, Qin D, Dokken DJ, Ebi KL, Mastrandrea MD, Mach KJ, Plattner GK, Allen SK, Tignor M, Midgley PM (eds) A special report of working groups I and II of the intergovernmetn panel on climate change. IPCC, Cambridge, UK and New York, NY. https://doi.org/10.1017/CBO9781139177245

  • Isaac ME, Dawoe E, Sieciechowicz K (2009) Assessing local knowledge use in agroforestry management with cognitive maps. Environ Manag 43:1321–1329. https://doi.org/10.1007/s00267-008-9201-8

    Article  Google Scholar 

  • Jose S (2009) Agroforestry for ecosystem services and environmental benefits: an overview. Agrofrestry Syst 76:1–10. https://doi.org/10.1007/s10457-009-9229-7

    Article  Google Scholar 

  • Kalaugher E, Bornman JF, Clark A, Beukes P (2013) An integrated biophysical and socio-economic framework for analysis of climate change adaptation strategies: the case of a New Zealand dairy farming system. Environ Model Softw 39:176–187. https://doi.org/10.1016/j.envsoft.2012.03.018

    Article  Google Scholar 

  • Kelly C, Ferrara A, Wilson GA, Ripullone F, Nol A, Harmer N, Salvati L (2015) Community resilience and land degradation in forest and shrubland socio-ecological systems: evidence from Gorgoglione, Basilicata, Italy. Land Use Policy 46:11–20. https://doi.org/10.1016/j.landusepol.2015.01.026

    Article  Google Scholar 

  • Kristjanson P, Place F, Franzel S, Thornton PK (2002) Assessing research impact on poverty: the importance of farmers’ perspectives. Agric Syst 72:73–92

    Article  Google Scholar 

  • Kristjanson Patti, Neufeldt H, Gassner A, Sayula G, Thiede B, Förch W, Thornton PK, Coe R (2012) Are food insecure smallholder households making changes in their farming practices? Evidence from East Africa. Food Sec 4:381–397. https://doi.org/10.1007/s12571-012-0194-z

    Article  Google Scholar 

  • Laws S, Harper C, Marcus R (2003) Research for development: a practical guide. Sage Publications, Inc, London, UK

  • Lott JE, Ong CK, Black CR (2009) Understorey microclimate and crop performance in a Grevillea robusta-based agroforestry system in semi-arid Kenya. Agric For Meteorol 149(1):1140–1151. https://doi.org/10.1016/j.agrformet.2009.02.002

    Article  Google Scholar 

  • Luedeling E, Sileshi G, Beedy T, Dietz J (2011) Carbon sequestration potential of agroforestry systems. Adv Agrofor 8(C):61–83. https://doi.org/10.1007/978-94-007-1630-8

    Article  Google Scholar 

  • Lykke AM (2000) Local perceptions of vegetation change and priorities for conservation of woody-savanna vegetation in Senegal. J Environ Manag 59(2):107–120. https://doi.org/10.1006/jema.2000.0336

    Article  Google Scholar 

  • Maponya P, Mpandeli S (2013) The role of extension services in climate change adaptation in Limpopo province, South Africa. J Agric Ext Rural Dev 5(7):137–142. https://doi.org/10.5897/JAERD12.117

    Article  Google Scholar 

  • Maranz S, Kpikpi W, Wiesman Z, De Saint Sauveur A, Chapagain B (2004) Nutritional values and indigenous preferences for shea fruits (Vitellaria Paradoxa C.F. Gaertn. F.) in African agroforestry parklands. Economic Bot 58(4):588–600. https://doi.org/10.1663/0013-0001(2004)058[0588:NVAIPF]2.0.CO;2

    Article  CAS  Google Scholar 

  • Martin SM, Lorenzen K (2016) Livelihood diversification in rural Laos. World Dev 83:231–243. https://doi.org/10.1016/j.worlddev.2016.01.018

    Article  Google Scholar 

  • Matocha J, Schroth G, Hills T, Hole D (2012) Integrating climate change adaptation and mitigation through agroforestry and ecosystem conservation. In: Nair PKR, Garrity D (eds) Agroforestry—the future of global land use, 9th edn. Spring Science+Business Media, Dordrecht. pp 105–127 https://doi.org/10.1007/978-94-007-4676-3

  • Mbow C, Smith P, Skole D, Duguma L, Bustamante M (2014) Achieving mitigation and adaptation to climate change through sustainable agroforestry practices in Africa. Curr Opin Environ Sustain 6:8–14. https://doi.org/10.1016/j.cosust.2013.09.002

    Article  Google Scholar 

  • Mbow C, Van Noordwijk M, Luedeling E, Neufeldt H, Minang PA, Kowero G (2014) Agroforestry solutions to address food security and climate change challenges in Africa. Curr Opin Environ Sustain 6(1):61–67. https://doi.org/10.1016/j.cosust.2013.10.014

    Article  Google Scholar 

  • McIntosh RJ (2000) Social memory in Mande. In: Mcintosh RJ, Tainter JA, McIntosh SK (eds) The way the wind blows. Columbia University Press, Dordrecht, pp 141–180

  • Mertz O, Mbow C, Nielsen JO, Maiga A, Diallo D, Reenberg A, Diouf A, Barbier B, Moussa IMB, Zorom M, Outtara I, Dabi D (2010) Climate factors play a limited role for past adaptation strategies in West Africa. Ecol Soc 15(4):25

  • Mertz O, Mbow C, Reenberg A, Diouf A (2009) Farmers’ perceptions of climate change and agricultural adaptation strategies in rural sahel. Environ Manag 43(5):804–816. https://doi.org/10.1007/s00267-008-9197-0

    Article  Google Scholar 

  • Mertz O, Mbow C, Reenberg A, Genesio L, Lambin EF, D’haen S, Zorom M, Rasmussen K, Diallo D, Barbier B, Moussa IB, Diouf A, Nielsen J, Sandholt I (2011) Adaptation strategies and climate vulnerability in the Sudano-Sahelian region of West Africa. Atmos Sci Lett 12:104–108. https://doi.org/10.1002/asl.314

    Article  Google Scholar 

  • Millennium Ecosystem Assessment (2005) Ecosystems and human well-being: synthesis. Island Press, Washington, DC

  • Mooney H, Larigauderie A, Cesario M, Elmquist T, Hoegh-Guldberg O, Lavorel S, Mace GM, Palmer M, Scholes R, Yahara T (2009) Biodiversity, climate change, and ecosystem services. Curr Opin Environ Sustain 1(1):46–54. https://doi.org/10.1016/j.cosust.2009.07.006

    Article  Google Scholar 

  • Mortimore M, Adams WM (1999) Working the Sahel: environment and society in northern Nigeria. Routledge, London and New York

  • Mortimore MJ, Adams WM (2001) Farmer adaptation, change and “crisis” in the Sahel. Glob Environ Change 11(1):49–57. https://doi.org/10.1016/S0959-3780(00)00044-3

    Article  Google Scholar 

  • Mulia R, Lusiana B (2018) Local knowledge on factors leading to agroforestry local knowledge on factors leading to agroforestry diversification in mid-hills of Nepal

  • Murray-Prior R (1998) Modelling farmer behaviour: a personal construct theory interpretation of hierarchical decision models. Agric Syst 57(4):541–556

    Article  Google Scholar 

  • Nair PKR (2014) Agroforestry: practices and systems. Encycl Agric Food Syst 1:270–282. https://doi.org/10.1016/B978-0-444-52512-3.00021-8

    Article  Google Scholar 

  • Niggli U, Fließbach A, Hepperly P, Scialabba N (2009) Low greenhouse gas agriculture: mitigation and adaptation potential of sustainable farming systems, vol Rev. 2. FAO, Rome, Italy

  • Norgrove L, Hauser S (2016) Biophysical criteria used by farmers for fallow selection in West and Central Africa. Ecol Indic 61:141–147. https://doi.org/10.1016/j.ecolind.2015.06.013

    Article  Google Scholar 

  • Okike I, Jabbar MA, Manyong VM, Smith JW, Jabbar MA, Manyong VM, Ecological, JWS (2017) Ecological and socio-economic factors affecting agricultural intensification in the West African savannas: evidence from northern Nigeria ecological and socio-economic factors affecting agricultural intensification in the West African savannas: evidence. J Sustain Agric 27(2):5–37. https://doi.org/10.1300/J064v27n02

    Article  Google Scholar 

  • Pandey DN (2002) Carbon sequestration in agroforestry systems. Clim Policy 2(4):367–377. https://doi.org/10.1016/S1469-3062(02)00025-6

    Article  Google Scholar 

  • Pelletier B, Hickey GM, Bothi KL, Mude A (2016) Linking rural livelihood resilience and food security: an international challenge. Food Secur 8(3):469–476. https://doi.org/10.1007/s12571-016-0576-8

    Article  Google Scholar 

  • Petit S (2003) Parklands with fodder trees: a Fulße response to environmental and social changes. Appl Geogr 23(2–3):205–225. https://doi.org/10.1016/j.apgeog.2003.08.008

    Article  Google Scholar 

  • Ræbild A (2012) Improved management of fruit trees in West African parklands. Agrofor Syst 85(3):425–430. https://doi.org/10.1007/s10457-012-9524-6

    Article  Google Scholar 

  • Reenberg A (1994) Land-use dynamics in the Sahelian zone in eastern Niger—monitoring change in cultivation strategies in drought prone areas. J Arid Environ 27:179–192

    Article  Google Scholar 

  • Rist S, Daubouh-Guebas F (2006) Ethnosciences—a step towards the integration of scientific and indigenous forms of knowledge in the management of natural resources for the future. Environ Dev Sustain 8:467–493. https://doi.org/10.1007/s10668-006-9050-7

    Article  Google Scholar 

  • Roncoli C, Ingram K, Kirshen P (2001) The costs and risks of coping with drought: livelihood impacts and farmers’ responses in Burkina Faso. Clim Res 19(2):119–132. https://doi.org/10.3354/cr019119

    Article  Google Scholar 

  • Rushemuka NP, Bizoza RA, Mowo JG, Bock L (2014) Farmers’ soil knowledge for effective participatory integrated watershed management in Rwanda: toward soil-specific fertility management and farmers’ judgmental fertilizer use. Agric Ecosyst Environ 183:145–159. https://doi.org/10.1016/j.agee.2013.10.020

    Article  Google Scholar 

  • Scoones I (1998) Sustainable rural livelihoods a framework for analysis. IDS Working Paper, vol 72. IDS, Brighton, UK. https://doi.org/10.1057/palgrave.development.1110037

  • Stack J (2009) Participatory approaches to research. In: Muir-Leresche K, Coe R, Ekwamu A (eds) Graduate environmental and agricultrual research: a guide to effective and relevant graudate research in Africa. Reginoal Universities Forum for Capacity Building in Africulture, pp 115–126

  • Sultan B, Roudier P, Quirion P, Alhassane A, Muller B, Dingkuhn M, Ciais P, Guimberteau M, Traore S, Baron C (2013) Assessing climate change impacts on sorghum and millet yields in the Sudanian and Sahelian savannas of West Africa. Environ Res Lett 8(1):14040. https://doi.org/10.1088/1748-9326/8/1/014040

    Article  Google Scholar 

  • Takimoto A, Nair PKR, Nair VD (2008) Carbon stock and sequestration potential of traditional and improved agroforestry systems in the West African Sahel. Agric Ecosyst Environ 125:159–166. https://doi.org/10.1016/j.agee.2007.12.010

    Article  CAS  Google Scholar 

  • Tappan G, Mcgahuey M (2007) Tracking environmental dynamics and agricultural intensification in southern Mali. Agric Syst 94:38–51. https://doi.org/10.1016/j.agsy.2005.07.011

    Article  Google Scholar 

  • Thien SJ (1979) A flow diagram for teaching texture by feel analysis. J Agron Educ 8:54–55

    Article  Google Scholar 

  • Tremblay G (2016) Adaptation strategies in the valley of the Senegal river: a social approach to dealing with climate change in Senegal. In: Agricultural adaptation to climate change. Spring International Publishing. pp 185–198. https://doi.org/10.1007/978-3-319-31392-4

  • Vanlauwe B, Coyne D, Gockowski J, Hauser S, Huising J, Masso C, Nziguheba G, Schut M, Van Asten P (2014) Sustainable intensification and the African smallholder farmer. Curr Opin Environ Sustain 8:15–22. https://doi.org/10.1016/j.cosust.2014.06.001

    Article  Google Scholar 

  • Waha K, Müller C, Bondeau A, Dietrich JP, Kurukulasuriya P, Heinke J, Lotze-Campen H (2013) Adaptation to climate change through the choice of cropping system and sowing date in sub-Saharan Africa. Glob Environ Change 23(1):130–143. https://doi.org/10.1016/j.gloenvcha.2012.11.001

    Article  Google Scholar 

  • Wolcott HF (1994) Transforming qualitative data: description, analysis, and interpretation. SAGE Publications, Inc, THousand Oaks, California

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Acknowledgements

We would like to thank everyone at l’Institut des Sciences de l’Envirronnment at Université Chiekh Anta Diop for their generous support of this project. In addition, the authors are grateful for the support of the provincial Kedougou authorities and the gracious hospitality from the communities involved. Lastly, we would like to thank the anonymous reviewers for their valuable comments and feedback. We would like to thank everyone at l’Institut des Sciences de l’Envirronnment at Université Chiekh Anta Diop for their generous support of this project. In addition, the authors are grateful for the support of the provincial Kedougou authorities and the gracious hospitality from the communities involved.

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This study was funded through the U.S. Borlaug Food Security Fellowship.

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Papa, C., Nzokou, P. & Mbow, C. Farmer Livelihood Strategies and Attitudes in Response to Climate Change in Agroforestry Systems in Kedougou, Senegal. Environmental Management 66, 218–231 (2020). https://doi.org/10.1007/s00267-020-01302-8

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