Climate change and human impact in a sensitive ecosystem: the Holocene environment of the Northwest Icelandic highland margin

Complex interactions of climate and volcanic activity have shaped the environment of Iceland during the Holocene. Palaeoecological records from Iceland offer a unique look at a Holocene environment that was uninhabited by humans and free of mammal herbivores until about AD 870. We present a new reconstruction of Holocene vegetation and landscape dynamics from a small lake, Baroalaekjartjorn, located near the highland margin in Northwest Iceland. A multi-proxy approach was used to reconstruct vegetation based on pollen and plant macrofossil analysis and landscape stability based on lithological proxies. The record covers the period c.10300-200cal. a BP. For the first two millennia aeolian processes probably played a part in vegetation development. This period is characterized by high input of minerogenic material into the lake and a vegetation assemblage in which plants tolerant of aeolian deposition are prominent. Betula pubescens woodland reached a maximum between c.7400 and 6500cal. a BP. Betula nana-dominated dwarf shrub heath replaced woodland after c.4000cal. a BP, following the onset of Neoglaciation. Land use following human settlement caused an environmental shift at the highland margin. Betula pubescens probably disappeared from the vicinity of the lake soon thereafter. Large-scale soil erosion began at c.1000cal. a BP in the wake of human activities, such as introduction of grazing livestock and woodcutting. This study offers an important long-term perspective of the development of the highland ecosystem under both wholly natural and human-influenced conditions.