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

Abstract

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, Barðalækjartjörn, 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. 10 300–200 cal. 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 6500 cal. a BP. Betula nana‐dominated dwarf shrub heath replaced woodland after c. 4000 cal. 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. 1000 cal. 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.

The multi‐component Hekla Ö Tephra, Iceland: a complex widespread mid‐Holocene tephra layer

“…The presence of the Hekla Ö tephra in soil sections in central and SE Iceland has been known for decades (Larsen and Vilmundardóttir, 1985;Gudmundsson, 1998). More recently, several studies have confirmed the widespread dispersal of the Hekla Ö tephra over Iceland (Gudmundsdóttir et al, 2011;Óladóttir et al, 2011;Sigurgeirsson and Hjartarson, 2011;Eddudóttir et al, 2016;Gudmundsdóttir et al, 2016Gudmundsdóttir et al, , 2018Jónsson, 2018), as well as in offshore sediments north of the island (Gudmundsdóttir et al, 2011). North and north-east of Hekla, the Hekla Ö tephra is frequently found in association with two other layers, the Hekla Mó tephra (ca.…”

“…Changes in (A) the silicic component and (B) the basaltic component of the Hekla Ö tephra as observed in distal deposits from east to west across Iceland. LÖG (Gudmundsdóttir et al , ), KAR, SNÆ, SAU, HRE, NÚP (Óladóttir et al , ), KVÍ (Gudmundsson, ), SVA, HER (this study), LGA, MD99‐2275 (Gudmundsdóttir et al , ), BAR, KAG (Eddudóttir, ; Eddudóttir et al , ; this study), SKR/SKO, (Gudmundsdóttir et al , ; Harning et al , ), BAE, TRK (Harning et al , ), NHV, DAG, REY, BRA (Gudmundsdóttir et al , ), HST (Hardardóttir et al , ; Jóhannsdóttir, ), HAK, HVÍ (Jóhannsdóttir, ), ARN (Gunnarsson, ), TAGL (Jónsson, ; this study), and MOS, ELL (Sigurgeirsson and Hjartarson, ). See Fig.…”

“…In recent years increased recognition of Hekla Ö in soil sections and lake sediments has been reported from distal areas as far as 200 km away from Hekla (e.g. Gudmundsdóttir et al, 2011Gudmundsdóttir et al, , 2016Óladóttir et al, 2011;Eddudóttir et al, 2016). Recently, considerations as to whether a tephra layer called Brattihjalli tephra is a part of the Hekla Ö tephra have been discussed by Gudmundsdóttir et al (2018) who suggested that thẽ 6060-6615 cal a BP Brattihjalli tephra in NW Iceland (Schomacker et al, 2016) represents the western part of the Hekla Ö, indicating an even more westerly distribution.…”

The rapid deglaciation of the Skagafjörður fjord, northern Iceland

“…About when the Saksunarvatn tephra was deposited, the dimensions of this local icecap were suggested to have been similar to its present dimensions, according to radiocarbon dating of pollen and macrofossil plants covered by the Saksunarvatn tephra in some Vestfirðir Peninsula lakes (Eddudóttir et al . , ; Harning et al . ).…”

Holocene tephrostratigraphy in Vestfirðir, NW Iceland

“…() showing the previously published distribution of Hekla Ö tephra (purple and red solid lines) and the proposed north‐westerly distribution (black dashed line). Purple circles show locations of identified Hekla Ö/Brattihjalli tephra in Vestfirðir and Barðalækjartjörn, north‐west Iceland (Eddudóttir et al ., ). Black dots show locations where the Hekla T layers have been reported in Lake Hestvatn (Jóhannsdóttir, ), Lake Hvítárvatn and Lake Arnavatn Stóra (Gunnarson, ).…”