«Philosophiae Doctor (PhD) Thesis 2007:20 Department of International Environment and Development Studies, NORAGRIC, Norwegian University of Life ...»
Philosophiae Doctor (PhD) Thesis 2007:20
Department of International Environment and Development Studies, NORAGRIC,
Norwegian University of Life Sciences • Universitetet for miljø- og biovitenskap
The Dynamics of Savanna Ecosystems and
Management in Borana, Southern Ethiopia
Philosophiae Doctor (PhD) Thesis 2007:20
Norwegian University of Life Sciences
NO–1432 Aas, Norway
Phone +47 64 96 50 00
www.umb.no, e-mail: firstname.lastname@example.org Ayana Angassa.indd 1 19.09.2007 07:54:16 The Dynamics of Savanna Ecosystems and Management in Borana, Southern Ethiopia Ayana Angassa PhD Thesis in Environment and Development Studies Department of International Environment and Development Studies, NORAGRIC, Norwegian University of Life Sciences (UMB) Ås, Norway Ås, 2007: 20 ISSN: 1503-1667 ISBN: 978-82-575-0762-6 Acknowledgements The research work was funded by the Norwegian Program for Development, Research and Education (NUFU), while the PhD stipend was covered by the quota program of the Norwegian State Educational Loan Fund (Lånekassen).
The writing of this thesis is obviously not possible without the personal and practical support of numerous people. First of all, I would like to thank God for the strength that He supplied to me for finalizing this work.
This thesis would not have been possible without the expert guidance of my esteemed supervisor, Professor Gufu Oba. I wish to express my deep gratitude to him for his follow up and encouragement throughout my study period. Not only was he readily available for me, but also he always read and responded to the drafts of each paper of my work more quickly than I could have hoped. His comments are always extremely perceptive, helpful, and appropriate. I am very grateful to Dr. Trygve Berg for his support and unreserved cooperation throughout my study period. I further would like to thank Anne Utvær, Jon Kr. Øiestad, Thorbjørn Gilberg and Håvard Reksten staff of the International Office at the Norwegian University of Life Sciences for their support in various ways throughout my study period.
I would like to express my profound gratitude to all staff and colleagues in the Department of International Environment and Development Studies, NORAGRIC for all the support and cooperation during my study period. Thanks for providing an intellectually stimulating and friendly working environment. I consider my nearly four and a half years at NORAGRIC to be a crucial learning period.
I am thankful for having received much assistance from librarians, especially Ingeborg Brandtzæg and Liv Ellingsen for their unreserved support and cooperation in meeting my enormous literature demand.
I would like to extend my deep appreciation to Joanna Boddens-Hosang for her unreserved cooperation in proof-reading of most of my papers and other technical support. Special thanks to Lars Øimoen for his technical support when problems arose with computer software and internet. Also thanks to Frode Sundnes, Josie Teurlings and Torunn Lindstad for their support and encouragement. I am thankful to Professor Frik Sundstøl for visiting my study sites in Borana. I deeply appreciate the welcome and encouragement I have received from Professor Ruth Haug, Head of Department. Many people at NORAGRIC assisted and encouraged me in various ways during my course of studies. I am especially grateful to Professor Shanmugaratnam, Professor Ian Bryceson, Dr. Randi Kaarhus, Professor Pål Vedeld, Professor Tom Burns, Professor Cary Fowler, Dr. Kjersti Larsen, Dr. Espen Sjaastad, Dr. Kjell Esser, Dr. Fred Johnsen and many others for all that they have taught me. I would like to thank Dr. T. A. Benjaminsen for his helpful comments.
I would like to thank the cooperation of Awassa College of Agriculture, Hawassa University formerly Debub University for handling all the administrative matters related to my study. I am especially grateful to Dr. Girma Abebe, Dr. Adugna Tolera, Dr. Fekadu Beyene, Dr. Admasu Tsegaye, Dr. Sheleme Beyene, Dr. Tegene Negesse, Professor Zinabu G/Mariam and Ato Awdenegest Moges for their encouragement and unreserved support in various ways during my study period. I would like to express my gratitude to Ageze Asegid, Messele Getachew, Mitiku Kassa, Zenebe, Dessalegn, Abinet, Katelo Guyo, Borbor Bule, Atilaw Belayneh, Kebede and Tafesse for their help during the tiresome tasks of fieldwork and sample collections. My special thanks go to Tadesse Bokore for assistance in the Lab work at Awassa College of Agriculture and Tigneh for his support in generating map of the study area.
The field research was conducted in Borana, southern Ethiopia. This work would not have been a reality without the cooperation, encouragement and advice of the Borana community during my fieldwork. I would like to thank the community and elders for welcoming me so warmly to Borana, for giving me frequent respite and much love since 1990. I am also indebted to staff and colleagues at the Southern Rangeland Development Unit (SORDU) and Borana cattle breed conservation ranch for the assistance rendered during my research work. Acknowledgement is also due to Professor Girma Gebresenbet, Dirba Dheresa, Hailu Dheresa, Ato Kebede K/Mariam, Dirba Temesgen, Bekelech Assefa, Habtamu Teka, Kenea Feyissa and the late Alemu Adare (former manager of SORDU) for their support and encouragement during my study period.
I am particularly thankful to colleagues Gutu Olana, Chaltu Dula, Teshome Hunduma, Dr.
Darley Jose Kjosavik, Dr. Poul Wisborg, Dr. Nawab, Dr. Robert, R. B., Eirin, Zeinabu, Deepack, Abebe Seifu, Ajebu Nurfata, Ayele Tesema, Waktole Tiki, Boku Tache, Adane Tufa, Hassan Guyo, Hussein Jemma, Etana Debela, Solomon Eyob, Fassill Bekele, Aster Abebe, Paoly, Dagim Jirata, Berhanu Abate, Zerhun Desta and Worku Tessema for their assistance and encouragement in various ways during my course of studies.
I would like to thank my parents for their prayers, encouragement, support, sacrifice and advice ever since my youth. Last but not least, I would like to thank my wife, Fetlework and my children Obse, Lemlem and Temesgen for all the support, love, encouragement and prayers. The support from all relatives and too many friends to list here is also acknowledged.
ii Table of contents
Table of contents
Lists of figures
1. General introduction
2. Theoretical considerations
2.1. The ecological models
2.1.1. The equilibrium model
2.1.2. The non-equilibrium model
2.2. Pastoral development policy
3. The study area
3.1. Borana rangelands of southern Ethiopia
3.2. Location and climate
3.2. Individual studies and methodological approach
3.3. Statistical analysis
4. Summaries of the main results
5.1. Cattle population dynamics
5.2. Herders’ environmental knowledge
5.3. Causes of bush encroachment
5.4. Demonstration of control methods
6. Implications for management and policy
8. Future research
Individual Papers I-V
Fig. 1. Map of the study area…………………………………………………………………14 Fig. 2. Map of specific sites…………………………………………………………………..15 iv Abstract Ayana Angassa. The dynamics of savanna ecosystems and management in Borana, southern Ethiopia. Department of International Environment and Development Studies, NORAGRIC, Norwegian University of Life Sciences (UMB).
This thesis discusses the dynamics of savanna ecosystems and management in southern Ethiopia by investigating the roles played by rainfall variability and the impact on cattle population under the communal rangelands and ranch system. The thesis considers the variability in terms of impact of multi-year droughts on livestock of different reproductive classes and their recovery patterns, comparing the traditional and ranch management systems. The thesis also investigates the importance of using herder environmental knowledge in understanding historical changes in patterns of land use and shifts in vegetation, with implications for pastoral production. Using herder concerns about shifts in grassland vegetation to bush encroachment, the thesis presents studies that examine the ecological mechanisms of bush encroachment in relation to protection, grazing and time of protection. The studies demonstrate the control of bush encroachment and evaluate the responses of individual woody and herbaceous species using six demonstrations.
This study is based on ecological models, focusing on the equilibrium and non-equilibrium models. The thesis seeks to understand the drivers of change behind cattle population variability, mechanisms of bush encroachment and effects of control demonstrations on woody and herbaceous plant species in Borana. Traditionally, the Borana land use system involves extensive livestock production based on mobility between the key and non-key resources. The thesis uses household interview and field based data collected between 2002 and 2005. Household cattle data (21 years) and the ranch cattle data (15 years) were related to long-term rainfall variability.
Breeding cows in the key resource tula well rangelands showed longer reproductive life than the non-key resource pond-water rangelands. Average calving rates were greater in the communal rangelands than in the ranch system. Severe mortality and greater reduction in calving rates during multiple droughts resulted in reduced herd growth potential. Inter-annual variability in rainfall seems to have a considerable effect on cattle populations compared to density dependence. The combined effects of variable rainfall and increased bush cover might lead to risks of drought induced herd dieoffs. Specifically, herder perceptions indicated that the emergence of range enclosures and expansion of crop farming have reduced the extent of grazing, while fire suppression has promoted bush encroachment.
Furthermore, the study found greater densities of invasive woody species in enclosures as opposed to the open grazed areas. This implies that additional causes might be involved in the process of bush encroachment apart from grazing. The use of the state-and-transition model showed complex successional pathways of changes with regard to variability in rainfall, management interventions and v timescales (i.e. the age chronosequence of enclosures) that are relevant for making management decisions.
The thesis suggests that protection from disturbance promotes bush encroachment. It was found that four out of the six bush control methods substantially reduced bushy plants, with varied effects on individual species. Overall, the tree cutting, fire and grazing treatment was more effective in controlling coppicing after disturbance. Different woody species showed varied adaptation strategies in response to disturbances by either adapting to increased seedling recruitment or coppicing after disturbance.
The disturbance control treatment had no advantage in terms of herbaceous biomass and basal cover over other treatments, while herbaceous species richness was enhanced. This thesis suggests that grazing with bush cover greatly reduces herbaceous biomass. Generally, tree cutting and fire seemed superior in terms of herbaceous biomass, while fire and grazing, and tree cutting are recommended for the conservation of herbaceous species diversity. The outcomes in terms of herbaceous biomass and species diversity have important policy implications for bush encroachment control and public education. This thesis emphasizes the importance of the fire and grazing method which can reasonably be recommended for control of bush encroachment with the overall objective of promoting herbaceous biomass and species diversity.
Results presented in this thesis suggest the following views: (i) The study acknowledges the evidence of density dependence at the level of local land use, but overall density independence at the regional level. The findings further confirm the failure of ranch management in reducing herd mortality and signify the role of rainfall variability even under a controlled system. The need for drought management, focusing on post-drought herd rehabilitation through the distribution of bulls, depends on the breed conservation ranch and is important for the maintenance of the Borana cattle breed; (ii) The use of communities’ environmental knowledge as a framework for understanding the impacts of land use change on the environment, may provide a strong foundation on which to reconstruct scientifically and culturally acceptable methodological approaches. Sustainable use of the savannas of southern Ethiopia in the future will require paying greater attention to regulating expansion of enclosures, crop farming and ranching, as well as re-introducing fire, where necessary, to control bush encroachment; (iii) The state-and-transition model is appropriate for describing the mechanisms of bush encroachment; (iv) Responses of individual woody and herbaceous species to bush control methods have important implications for management, conservation policy and public education which in the future should be promoted through public education and extension.
vi1. General introduction
The thesis examines the dynamics of savanna ecosystems and management in Borana, southern Ethiopia, by investigating the role played by long-term rainfall variability on cattle populations managed under the communal rangelands (i.e. key and non-key resource grazing lands) and the ranch management system. The thesis considers the variability in terms of the impact of multi-year droughts on livestock of different reproductive classes and their recovery patterns, comparing the traditional and the ranch management systems. Specific hypotheses were posed and tested in a comparative study.