During the nineteenth century, ivory hunting caused a substantial decrease of elephant numbers in southern Africa. Soon after that, populations of many other large and medium-sized herbivores went into steep decline due to the rinderpest pandemic in the 1890s. These two events provided an opportunity for woodland establishment in areas previously intensively utilized by elephants and other herbivores. The return of elephants to currently protected areas of their former range has greatly influenced vegetation locally and the resulting potential negative effects on biodiversity are causing concern among stakeholders, managers, and scientists.

This book focuses on the ecological effects of the increasing elephant population in northern Botswana, presenting the importance of the elephants for the heterogeneity of the system, and showing that elephant ecology involves much wider spatiotemporal scales than was previously thought. Drawing on the results of their research, the authors discuss elephant-caused effects on vegetation in nutrient-rich and nutrient-poor savannas, and the potential competition between elephants on the one hand and browsers and mixed feeders on the other.

Ultimately this text provides a comprehensive review of ecological processes in African savannas, covering long-term ecosystem changes and human-wildlife conflicts. It summarises new knowledge on the ecology of the sub-humid African savanna ecosystems to advance the general functional understanding of savanna ecosystems across moisture and nutrient gradients.

Christina Skarpe is a Professor in Applied Ecology at the Faculty of Applied Ecology and Agricultural Sciences at Hedmark University College, Norway. Her main research interest is large herbivores and African savanna ecology. From Uppsala University, Sweden, Botswana Ministry of Agriculture and later from Norwegian Institute of Nature Research and Hedmark University College she concentrated on herbivores- and worked on diverse projects in Africa, Scandinavia, China and Central America.

Johan du Toit is Professor of Ecology and Conservation of Large Mammals in the Wildland Resources Department at Utah State University, USA. He has almost 30 years experience conducting ecological research in African savanna ecosystems. At the University of Zimbabwe he coordinated the Tropical Resource Ecology Programme, after which he was the Austin Roberts Professor of Mammalogy and Director of the Mammal Research Institute at the University of Pretoria. His research focus is the ecology and conservation of large mammals in terrestrial ecosystems.

Stein R. Moe is a Professor of Ecology at the Norwegian University of Life Sciences, Norway. Although his scientific works span over four continents, his main focus has been on African savanna ecology. He is currently coordinating a Masters program in tropical ecology and natural resource management in the Department of Ecology and Natural Resource Management. Following several years as a departmental board member, he is now a member of the faculty board at the University.

List of Contributors xi

Foreword xiii
Norman Owen-Smith

Preface xvii

Part I The Chobe Ecosystems 1

1. Introduction 3
Christina Skarpe and Stein R. Moe

2. The Chobe Environment 7
Christina Skarpe and Susan Ringrose

3. Elephant-Mediated Ecosystem Processes in Kalahari-SandWoodlands 30
Johan T. du Toit, Stein R. Moe and Christina Skarpe

Part II The Substrate 41

4. Historical Changes of Vegetation in the Chobe Area 43
Christina Skarpe, Håkan Hytteborn, Stein R. Moe and Per Arild Aarrestad

5. Vegetation: Between Soils and Herbivores 61
Per Arild Aarrestad, Håkan Hytteborn, Gaseitsiwe Masunga and Christina Skarpe

Part III The Agent 89

6. Guns, Ivory and Disease: Past Influences on the Present Status of Botswanas Elephants and their Habitats 91
Mark. E. Vandewalle and Kathy. A. Alexander

7. The Chobe Elephants: One Species, Two Niches 104
Sigbjørn Stokke and Johan T. du Toit

8. Surface Water and Elephant Ecology: Lessons from a Waterhole-Driven Ecosystem, Hwange National Park, Zimbabwe 118
Simon Chamaillé-Jammes, Marion Valeix, Hillary Madzikanda and Hervé Fritz

Part IV Controllers 133

9. Soil as Controller of and Responder to Elephant Activity 135
Christina Skarpe, Gaseitsiwe Masunga, Per Arild Aarrestad and Peter G.H. Frost

10. Impala as Controllers of Elephant-Driven Change within a Savanna Ecosystem 154
Stein R. Moe, Lucas Rutina, HåkanHytteborn and Johan T. du Toit

11. Buffalo and Elephants: Competition and Facilitation in the Dry Season on the Chobe Floodplain 172
Duncan J. Halley, Cyril Taolo and Stein R. Moe

Part V Responders 187

12. PlantHerbivore Interactions 189
Christina Skarpe, Roger Bergström, Shimane Makhabu, Tuulikki Rooke, Håkan Hytteborn and Kjell Danell

13. Elephants and the Grazing and Browsing Guilds 207
Christina Skarpe, Stein R. Moe, MärthaWallgren and Sigbjørn Stokke

14. Cascading Effects on Smaller Mammals and Gallinaceous Birds of Elephant Impacts on Vegetation Structure 229
Sigbjørn Stokke, Sekgowa S. Motsumi,Thato B. Sejoe and Jon E. Swenson

15. The Chobe Riverfront Lion Population: A Large Predator as Responder to Elephant-Induced Habitat Heterogeneity 251
Harry P. Andreassen, Gosiame Neo-Mahupeleng, Øystein Flagstad and PerWegge

Part VI Elephants in Social-Ecological Systems 269

16. Human Dimensions of Elephant Ecology 271
Eivin Røskaft, Thor Larsen, Rapelang Mojaphoko, A. H. M. Raihan Sarker and Craig Jackson

17. Elephants and Heterogeneity in Savanna Landscapes 289
Johan T. du Toit, Christina Skarpe and Stein R. Moe

Index 299