The Impact of Settlement on Woodland Resources in Viking Age Iceland Nikola Trbojević Dissertation towards the degree of Doctor of Philosophy University of Iceland The School of Humanities Faculty of History and Philosophy June 2016 Sagnfræði- og heimspekideild Háskóla Íslands hefur metið ritgerð þessa hæfa til varnar við doktorspróf í fornleifafræði Reykjavík, 13. april 2016 Svavar Hrafn Svavarsson deildarforseti Faculty of History and Philosophy at the University of Iceland has declared this dissertation eligible for a defense leading to a PhD degree in Archaeology Doctoral committee: Orri Vésteinsson, supervisor Hans Skov-Petersen Þröstur Eysteinsson The Impact of Settlement on Woodland Resources in Viking Age Iceland © Nikola Trbojević Reykjavík 2016 Thesis for a doctoral degree at University of Iceland. All rights reserved. No part of this publication may be reproduced in any form without the prior permission of the copyright holder. ISBN 978-9935-9260-6-7 Printed by: Háskólaprent ehf. Abstract The settlement of Iceland in the late 9th and early 10th centuries – the landnám – is associated with a large scale deforestation which resulted in significant and long-term consequences for the island’s fragile environment. The landnám deforestation has been the focus of academic research for more than a century, but its process and reasons remain poorly understood. The size of the pre-landnám forests has not been established and it remains unclear whether the deforestation was an unavoidable effect of human colonisation, whether it was the result of a deliberate strategy or whether it was a case of mismanagement. The aim of this dissertation is to throw light on these issues. It establishes an estimate of the extent of the pre-landnám forests and shows that even the most generous estimates for the settlers’ requirements for fuel and building material would not have made an appreciable impact on the woodlands. Rather it was clearance for pastures and home-fields which was the cause of the large scale deforestation. The deforestation process is explored through four possible scenarios of available manpower and social relations. The scenarios are processed through a series of spatially explicit agent-based models of three sample study areas: Vestur- Eyjafjallahreppur, Mývatn and Borgarfjörður. The outcomes of those models suggest that the deforestation was the result of a deliberate strategy to establish and develop an economy based on animal husbandry. This strategy was however applied without a full awareness of the potential and the fragility of the local environments. Very early on, the newly created pastures began to suffer degradation and their grazing potential declined. The decline was caused by a combination of overgrazing, the spread of grazing-tolerant vegetation, and to a lesser degree, by woodland regrowth. As a result, the initial extent of cleared pastures proved insufficient, requiring repeated re-initiation of clearance at many locations. The model outcomes also suggest that the deforestation was neither as drastic nor as rapid as it has commonly been portrayed. Although most of the deforestation had taken place already before the end of the 9th century, it was a drawn-out process which lasted throughout the 10th century and most likely continued well into the post-landnám periods. iii Ágrip Landnám Íslands seint á 9. öld og í byrjun 10. aldar hafði í för með sér stórfellda skógar- eyðingu með víðtæk og langvarandi áhrif á viðkvæma náttúru landsins. Skógareyðing landnámsaldar hefur verið rannsökuð í meira en öld en ekki hefur verið skýrt hvernig skógareyðingin átti sér stað né hvað olli henni. Stærð skóglendis fyrir landnám er ekki þekkt og óljóst er hvort skógareyðingin var óhjákvæmileg aukaverkun landnáms manna og dýra, hvort hún var afleiðing af meðvitaðri stefnu eða ofnýtingu. Markmið ritgerðarinnar er að varpa ljósi á þetta mál. Lagt er mat á stærð skóglendisins fyrir landnám og sýnt fram á að þörf landnámsmanna fyrir eldsneyti og byggingarefni ein og sér, jafnvel ef mjög rúmt er áætlað, hefði ekki getað haft þessi miklu neikvæðu áhrif á skóglendið. Skógarhögg í þeim tilgangi að rýma fyrir túnum og skapa víðfeðm beitilönd var ástæða hinnar stórfelldu skógareyðingar. Til að rannsaka framgang skógareyðingarinnar eru skilgreindar fjórar sviðsmyndir sem byggja á mismunandi forsendum með tilliti til tiltæks mannafla og félagslegra tengsla. Til að kanna sviðsmyndirnar eru „agent-based“ tölvulíkön keyrð fyrir þrjú rannsóknarsvæði: Vestur-Eyjafjallahrepp, Mývatn og Borgarfjörð. Niðurstöður tölvulíkananna sýndu að skógareyðingin var afleiðing vísvitandi stefnu sem hafði það að markmiði að stofna og þróa samfélag byggt á búfjárrækt. Þessari stefnu var hins vegar framfylgt án fulls skilnings á þolmörkum umhverfisins á hverjum stað. Mjög fljótlega fór að bera á hnignun landgæða á hinum nýju beitilöndum og afrakstur þeirra minnkaði. Þessi hnignun orsakaðist af ofbeit, útbreiðslu beitarþolins gróðurs og einnig, þó í minna mæli, af endurvexti skóga. Upphaflegt umfang af ruddum svæðum reyndist ekki nægjanlegt og því varð víða nauðsynlegt að hefja aftur skógarruðning fyrir nýju beitilandi. Niðurstöður tölvulíkananna gefa einnig til kynna að skógareyðingin hafi hvorki verið eins stórfelld né eins hröð og oft hefur verið haldið fram. Þó svo að skógareyðingin hafi að stærstum hluta átt sér stað fyrir lok 9. aldar, náði heildarferlið yfir mun lengra tímabil sem stóð yfir alla 10. öldina og hélt að öllum líkindum áfram löngu eftir landnám. v Acknowledgements The work on this project was carried out at the Faculty of History and Philosophy, School of Humanities at the University of Iceland, and it was accomplished thanks to the funding provided by the Landsvirkjun Orkurannsóknasjóður and support of the University of Iceland. Many people have helped me to conclude this journey and I am more than grateful for that. I would like to thank my supervisor, Professor Orri Vésteinsson (University of Iceland) for an amazing guidance, unlimited patience and readiness to help at any moment. It has been a privilege to work with him. Many thanks also goes to other members of my doctoral committee: Þröstur Eysteinsson (Iceland Forest Service), for his continual help, incredibly detailed explanations and extremely valuable suggestions; Hans Skov-Petersen (University of Copenhagen), for helping me with the first steps in the world of agent-based modelling, for his advice and support and for being a kind host during my time spent in Denmark. I would also like to thank all my friends and colleagues in Reykjavík and elsewhere, for their support, help and of course, coffee and beer breaks, which were sometimes necessary to keep the spirit up. A special thanks goes to all the people of the Institute of Archaeology, Iceland and the North Atlantic Biocultural Organisation. I would also like to thank researchers from the Iceland Forest Service as well as the Icelandic Institute of Natural History. I also wish to express my gratitude to the opponents: Professor John Wainwright (University of Durham) and Dr. Kristín Svavarsdóttir (Soil Conservation Service of Iceland) for their comments and suggestions. A very special thanks goes to my family – my dear Hulda Sif, for being there all the time and for keeping me sane all these years and my little daughter Silja Björt, for putting a smile on my face during the grey days. Finally, I would like to thank my parents, without whose incredible support and limitless encouragement it would never have been possible to accomplish this kind of work. vi Contents Abstract ................................................................................................................................... iii Ágrip ......................................................................................................................................... v Acknowledgements .................................................................................................................. vi List of figures ........................................................................................................................... xi List of tables ........................................................................................................................... xvi Appendices ............................................................................................................................. xix 1 Introduction .................................................................................................................... 1 1.1 The subject of the study ....................................................................................................... 1 1.2 The study period .................................................................................................................. 4 1.3 Objectives of the study ........................................................................................................ 4 1.4 Thesis outline ....................................................................................................................... 5 2 Present state of knowledge on the landnám deforestation ........................................... 7 2.1 Introduction .......................................................................................................................... 7 2.2 The written sources .............................................................................................................. 7 2.3 Modern research and the major disciplines involved .......................................................