Optimising the trade-offs between food production, biodiversity and ecosystem services in the Neotropics David Rhodri Williams Department of Zoology University of Cambridge This dissertation is submitted for the degree of Doctor of Philosophy Clare College June 2016 This thesis is dedicated to Katherine Claire Williams Declaration I hereby declare that except where specific reference is made to the work of others, the contents of this dissertation are original and have not been submitted in whole or in part for consideration for any other degree or qualification in this, or any other university. This dissertation is my own work and contains nothing which is the outcome of work done in collaboration with others, except as specified in the text and Acknowledgements. This dissertation contains fewer than 65,000 words including appendices, bibliography, footnotes, tables and equations and has fewer than 150 figures. David Rhodri Williams June 2016 Acknowledgements I am extremely grateful to my supervisor Andrew Balmford for his support, encour- agement, advice and gentle mockery over the past four years. Andrew, together with my advisers Rhys Green and Andrea Manica, have helped me to clarify and greatly improve my thinking and writing, and have given me invaluable advice on my research and my career. In Mexico, I would have been lost without the help and guidance of Pancho Galindo and Paul Wood, for which I am incredibly grateful. I would like to thank the Natural Environment Research Council, the University of Cambridge and the Department of Zoology for financial support, as well a large number of other organisations: the Tim Whitmore Fund from the Department of Zoology, the Cambridge Philosophical Society, the Cambridge Society for the Application of Research, the Mary Euphrasia Mosley, Sir Bartle Frere & Worts Travel Funds, the T H Middleton Fund, Santander Student Travel Grants and Clare College, Cambridge. Planning this research relied on the expertise and goodwill of dozens of people. Particular thanks to Ben Phalan and Claire Feniuk, without whom I would have been in a world of trouble. Other great advice early in the project came from Toby Gardener, Jared Margulis, Chris Sandbrook, Bill Thorpe, Tania Urquiza and Jess Walsh. In the field I am indebted to a huge number of people, in particular Paul andPatty Wood; Pancho, Ana and Luciana and Amelia; Rafa and his students from UNAM and UADY, especially Angel and Mario; as well as all the ranchers, campesinos and milperos who were incredibly welcoming and helpful and gave me access to their land. Special thanks to Dr. Rolando, Don Victor, Don Eduardo and Don Santiago. Dr. Sergio Nunoz, Sergio Rico Ponce, Adriana Hernandez, everyone at ProNatura, Dr. Juan Ku, Dr. Juan Jiminez-Osornio and Dr. Juan Chable all offered me excellent advice for planning my fieldwork, and I would like to give a huge thanks to the anonymous interviewees who put up with my bad Spanish and irritating questioning to give me some invaluable insights into the world of Mexican environmental and agricultural policy. Finally, huge thanks to my indomitable field assistants who kept me sane and viii ensured I could actually do my fieldwork: Margarita, Becky, Tim, Victor, Ramiro, Edi and Don Miguel, thanks a lot! I have relied heavily on everyone in the Conservation Science Group in Cambridge - it has been a real pleasure to work here and I’ve learned so much from so many people. A special mention to the Dream Team of Claire, Little Andrew and Lizzy, with honourable mentions for the late-comers Anthony, Tim and Erasmus. Bill, Jon, Kelvin, Lynn and Tatsuya have also been hugely helpful both in my PhD and beforehand. In Mexico, Fredy and Federico in Inecol and Carlos, Gerardo, Rafa and everyone else in UNAM who gave me all the time, advice and support I could wish for. Before my PhD, the BCM class of 2009-2010 helped shape a lot of my thinking, with Jared, Tarsh, Claudia and Lydia especially always offering support and a good argument. Outside of work there are more people to thank than I have room for: Graham, Owen and Sammy are the best friends that you could hope to have, and a constant source of amusement and withering criticism. The hordes of people passing through Pelham Court have made the last four years a huge amount of fun, so thanks to Rob the Hoboworm, Oscar, Max, Caitlin, Tommy, Mark and Cat amongst an unknown number of others. Thanks to the Clare MCR, especially Adam, Freddie and Megan for so many “just one more” pints and the subsequent loss of intellectual ability. A smorgasbord of other wonderful people have also helped me survive: Amin Oomatia, Anna Hobbiss, Charlie Clift, Davy Evans, Eithne James, Emma O’Brien, Fionnuala Ratcliffe, James Clemence, Johnny Austin, Kate Tomlinson, Matt Child, Olga Dziewulska and Pippa Hardingham are some but not all of them. Finally, there are no words to describe my gratitude to Caroline, Ed, and their enormous welcoming families and most of all to my father and my sister, Michael and Helen who have encouraged and inspired me for as long as I can remember. Summary Agriculture is the greatest threat to biodiversity across the world and a major con- tributor to anthropogenic greenhouse gas emissions. Both pressures will increase over coming decades as populations and per capita consumption rise. How we choose to produce food will, to a large extent, determine the state of biodiversity and the wider environment in the 21st century. Balancing livestock production and environmental concerns is of particular impor- tance: rangelands cover approximately one quarter of the world’s ice-free land and livestock consume over one third of all calories from crops. In addition, livestock, particularly ruminants are extremely inefficient and use more land, nitrogen and water than other foodstuffs, whilst producing more2 CO . Finally, there is a strong relationship between wealth and meat consumption. Combined with increasing populations, this means that demand for meat is likely to continue to increase. Two alternative strategies have been proposed to minimise the environmental cost of food production: land sharing attempts to maximise biodiversity within the farmed landscape by keeping yields artificially low. Alternatively, land sparing links high yield agriculture with increased habitat protection or restoration. Previous studies have examined the relative benefits of the two strategies in different agricultural systems and regions. However, my research is the first to look at a wide range of alternative livestock production systems in a highly disturbed part of the tropics. To investigate this issue I collected data on the production and requirements of different cattle ranching systems in Yucatán, Mexico, as well as on the population densities of birds, trees and dung beetles, and carbon stocks in both natural habitats and the different ranching systems. I used novel methods to estimate the yieldsof my study sites and applied both previously developed density-yield functions and new scenario building methods to model how species and carbon stocks responded to increasing agricultural yields. I found that all taxa, and carbon stocks, show similar responses: rapidly declining with conversion from natural habitats to agricultural land. The populations of most x species, and regional carbon stocks, were therefore maximised with a land-sparing strategy that combines high yields with forest protection or restoration. Such as strategy is broadly aligned with the goals of producers, environmental organisations and policy makers in Yucatán. However, mechanisms for active land sparing, which can link yield increases with habitat protection, will be needed to ensure that the benefits of land sparing can be realised. In addition, even with land sparing, probable 2030 production targets still resulted in forest loss, highlighting the need for demand reduction as an important part of a sustainable food strategy. Abbreviations and glossary AIC Akaike’s Information Criteria, a measure of the relative quality of a model’s fit AICc AIC corrected for small sample sizes C Carbon CO2 Carbon dioxide CONABIO Comisión Nacional para el Conocimiento y Uso de la Biodiversidad – the Mexican National Commission for the Knowledge and Use of Biodiversity dbh Diameter at breast height, diameter at 1.3 m from the ground — a standard measure of tree diameter Dressing percent- The ratio of carcass weight to live weight for livestock, a measure of age the amount of edible meat in an animal EOO Extent of Occurrence. A measure of the global range of a species, used by e.g. BirdLife International GPS Global Positioning System ha Hectare (100 x 100 m) INECOL Instituto de Ecología – the Institute of Ecology, Xalapa, Veracruz, Mexico INEGI Instituto Nacional de Estadística y Geografía. – the Mexican National Institute for Statistics and Geography ISPS Intensive Silvopastoral Systems, a livestock production system com- bining pastures with banks of protein-rich legumes such as Leucaena leucocephala planted at high densities IUCN International Union for the Conservation of Nature km Kilometer. 104 metres kg Kilogram. 104 grams m Metre xii Mg Megagram. 106 grams, 1000 kg, or 1 tonne N Nitrogen PROGAN Producción Pecuaria Sustenabley Ordenamiento Ganadero y Apícola – Programme for the Sustainable Production and Management of Livestock and Beekeeping, a Mexican subsidy programme to support smallholder ranchers REDD United Nations Collaborative Programme on Reducing Emissions from Deforestation and Forest Degradation