Landscape change in the Icelandic highland: A long-term record of the impacts of land use, climate and volcanism

Publisher's version (útgefin grein)Agriculture has been practiced in Iceland since settlement (landnám; AD 877). This has caused changes in vegetation communities, soil erosion, desertification and loss of carbon stocks. Little data exist regarding vegetation and ecosystems in the Icelandic highland before landnám and therefore the impact of land use over time is poorly understood. The objectives of the study are to examine the timing, nature and causes of land degradation in the highland of Northwest Iceland. Specifically, to determine the resilience of the pre-landnám highland environment to disturbances (i.e. climate cooling and volcanism) and whether land use pressure was of sufficient magnitude to facilitate ecosystem change. A sediment core was taken from the highland lake Galtaból. A chronology for the core was constructed using known tephra layers and radiocarbon dated plant macrofossils. Pollen analysis (vegetation), coprophilous fungal spores (proxy for grazing), and sediment properties (proxies for erosion) were used to provide a high-resolution, integrated vegetation and paleoenvironmental reconstruction. The pre-landnám environment showed resilience to climate cooling and repeated tephra fall. Soon after landnám the vegetation community changed and instability increased, indicated by changes in sediment properties. The pollen and spore record suggest introduction of grazing herbivores into the area after landnám. Following landnám, indicators of soil erosion appear in the sediment properties. Intensification of soil erosion occurred during the 17th century. The Galtaból record clearly demonstrates what can happen in landscapes without adequate management of natural resources and underestimation of landscape sensitivity. Introduction of land use resulted in changes in vegetation communities, loss of resilience and onset of increased soil erosion. Paleoenvironmental reconstructions may inform future decisions on management of the highland by providing baselines for natural variability in the pre-landnám environment.The authors would like to thank Þorsteinn Jónsson and Höskuldur Þorbjarnarson for assistance in the field. Jessica Lynn Till is thanked for proofreading the manuscript. We would like to thank Leone Tinganelli for his work on milling sediment samples for C and N analysis. The Blönduvirkjun hydropower plant kindly hosted us during fieldwork. The authors would like to thank three anonymous reviewers for their valuable comments and suggestions. The research was funded by the Landsvirkjun Energy Research Fund, the University of Iceland Research Fund, and the Icelandic Research Fund (grant no. 141842-051 ).Peer Reviewe