Mammalian community responses to a gradient of land-use intensity on the island of Borneo Oliver Richard Wearn Division of Ecology and Evolution Department of Life Sciences Imperial College London A thesis submitted for the degree of Doctor of Philosophy 2015 ii Copyright declaration The copyright of this thesis rests with the author and is made available under a Creative Commons Attribution Non-Commercial No Derivatives licence. Researchers are free to copy, distribute or transmit the thesis on the condition that they attribute it, that they do not use it for commercial purposes and that they do not alter, transform or build upon it. For any reuse or distribution, researchers must make clear to others the license terms of this work. iii Abstract Southeast Asian rainforests have, in recent decades, experienced the highest rates of deforestation and logging across the major tropical regions. This has left a vast estate of degraded forest in the region, which is under threat from further degradation and conversion to agriculture, principally for the expansion of oil palm (Elaeis guineensis) plantations. However, knowledge of the relative conservation value of different land-uses in the region is still limited, and a robust quantitative basis for resolving land-use tradeoffs, in particular between agricultural yield and biodiversity, is lacking. I aimed to assess terrestrial mammal species richness, abundance and β-diversity across a gradient of land-use intensity (old-growth forest, logged forest and oil palm) in Sabah, Malaysian Borneo. Overall mammal species richness was conserved even in the intensively-logged forests that I sampled, as were the majority of apparent old-growth specialists. Oil palm, on the other hand, harboured a highly depauperate mammal community. These broad patterns were echoed for overall mammal abundance, as well as in the potential ecosystem functions of mammals that I examined. However, I found evidence that the fundamental drivers of community assembly were altered across the land-use gradient and so, consequently, were patterns of β-diversity. Fine-grained β-diversity, in particular, was highest across the land-uses in logged forest, reflecting the increased environmental heterogeneity in this habitat. In addition, community composition and species abundance were not stable across land-uses. Omnivores and herbivores were more abundant in logged forest compared to old-growth forest, and only a limited number of carnivore species persisted in oil palm. Invasive species increased in abundance with land-use intensity. My findings underline the conservation importance of the large areas of degraded forest in Southeast Asia, and the extremely limited value offered by oil palm. If sustainability of the palm oil industry is to be achieved, new plantations should be diverted away from all remaining unfragmented forests, both old-growth and degraded forests alike. iv Acknowledgements Inevitably, the acknowledgements that follow are but the tip of the iceberg of the many and varied people and organisations that, in no small part, helped me at all stages in the formation of this thesis. To all those people not mentioned here, rest assured I remain wholly indebted to you. Firstly, I acknowledge my principal funder, the Sime Darby Foundation, as well as the Zoological Society of London, for providing the resources needed to complete this work. I acknowledge the Economic Planning Unit and, latterly, the Sabah Biodiversity Council, for allowing me to conduct research in Malaysia. I also appreciate the agreement from the Sabah Forestry Department, Yayasan Sabah, the Maliau Basin Management Committee, Benta Wawasan and Sabah Softwoods to allow research to be done in their respective areas. I am grateful for the support I received from the Royal Society South East Asia Rainforest Research Programme and am especially indebted to Glen Reynolds and his team for the huge amount of logistical assistance I received in-country. I extend my thanks also to Henry Bernard, my local collaborator, for kindly obliging with all my requests for research or logistical support in Sabah. An emphatic word of thanks must go to my supervisory team: Rob Ewers, Chris Carbone and Marcus Rowcliffe. Thank-you for all of the ideas and counsel you gave me during my Ph. D. I couldn’t have asked for a better team and your supervision was always absolutely spot-on. I’ve learnt a lot from you all and will miss the sometimes confusing, sometimes enlightening, meetings we’ve had over the years. I am also grateful to my broader supervisory panel, Tim Coulson and E. J. Milner-Gulland, for the insightful feedback they provided during the earlier stages of my Ph. D. Of everyone involved in this thesis, I am most deeply indebted to the research assistants who helped me to collect the data out in Borneo, often shedding blood (if the leeches got their way), sweat and tears in the process, with apparently little reward. To Leah Findlay, Matt Holmes, Faye Thompson, v Jack Thorley and Jess Haysom, thank-you all for being superlative in the field, always rising to meet whatever challenge was thrown at us and, quite obligingly, for putting up with me in the field. You have all learned a life-time supply of free beer on me. Thank-you also to Jeremy Cusack and Robin Loveridge for being great field companions and, of course, for sharing the heavy work-load on Team Tikus. It was an absolute pleasure to work with you. Thank-you so much, also, to the many and varied people who helped form the tapestry of social life at the SAFE “temporary camp” that we called a home from home. It pains me that I am unable to name everyone individually here in the limited space available, but thanks in particular to the rest of the “trinity”, Sarah Luke and Claudia Gray, as well as Timm Döbert, Terhi Riutta, Jen Sheridan and James Rice for making field life that much more enjoyable. I could not have achieved the back-breaking task of collecting data on elusive mammals without the tireless work of staff at the SAFE Project. In particular, Matiew bin Tarongak, James Loh, Mohd Sabri bin Bationg and Aleks Warat Koban bin Lukas should all be applauded for working so tirelessly and diligently in the field. Even when the day involved lugging 100 steel traps up the face of a slippery hillside, it was a pleasure with you guys. The help of Ed Turner, MinSheng Khoo, Johnny Larenus, Sarah Watson and Ryan Gray was also absolutely invaluable in making the fieldwork even remotely possible. During my, admittedly limited, time spent in the UK working in my two institutions – both at Silwood Park and at the Institute of Zoology – I’ve also had the great pleasure of working with a fantastic bunch of people over the years. I thank everyone I’ve ever shared an office with for making the write- up just that bit more bearable and in particular all of the “FEC” lab group, both past and present. I am especially grateful for the inordinate amount of help that Marion Pfeifer provided with all things RapidEye. vi Lastly, I am deeply grateful to my family for their constant support and encouragement, and for their unquestioning accommodation of my tropical wanderlust over the years before and during the making of this thesis. vii Declaration of originality R. M. Ewers, C. Carbone and J. M. Rowcliffe contributed at all stages of the thesis, including the conception, design and analysis. All further assistance received is detailed below. Chapter 1: R. M. Ewers and E. J. Milner-Gulland commented on an earlier draft of this chapter. Chapter 2: R. M. Ewers, J. M. Rowcliffe, C. Carbone and H. Bernard provided extensive comments on this chapter. M. Linkie and an anonymous reviewer also greatly helped to improve the manuscript during submission to PLoS One. Chapter 3: R. M. Ewers, C. Carbone, J. M. Rowcliffe and H. Bernard all provided comments on an earlier draft of this chapter, which greatly assisted in improving the clarity of the presentation. Chapter 4: R. M. Ewers and C. Carbone provided helpful comments on this chapter. M. Pfeifer pre- processed the RapidEye satellite images and ran the models of above-ground live tree biomass, of which the mapped outputs featured in my modelling of community assembly. These maps were provided as part of an ongoing collaborative effort at the SAFE Project. Chapter 5: R. M. Ewers, J. M. Rowcliffe and C. Carbone provided comments on this chapter. M. Tobler provided helpful feedback on an earlier version of one of the hierarchical models used. The Imperial College High Performance Computing facility was used to run the bulk of the analysis. M. Pfeifer’s above-ground live tree biomass estimates were again used in this chapter. Chapter 6: R. M. Ewers, J. M. Rowcliffe and C. Carbone all provided comments on this chapter. I herewith certify that all other material in this thesis is solely the result of my own work. viii Table of contents Copyright declaration .......................................................................................................................... iii Abstract ................................................................................................................................................. iv Acknowledgements ............................................................................................................................... v Declaration of originality .................................................................................................................. viii Table of contents .................................................................................................................................