Environmental impacts of the Norse settlement: palaeoenvironmental data from Myvatnssveit, northern Iceland

The first stratigraphically continuous pollen profile spanning the Norse and Medieval periods from the archaeoloically-rich Myvatnssveit region of northern Iceland is presented. Detailed analyses were made of the tephra, sediment characteristics, pollen and chironomids of a 3 kyr sediment sequence from Helluvaostjorn, a small. shallow lake. The pollen data show a steady decline in the percentage abundance of tree birch (Betula pubescens) pollen between the Norse settlement (landnum, c. AD 870) and c. AD 1300, a pattern that contrasts with the abrupt fall in birch pollen percentages immediately following the Norse colonization at almost all previously studied sites in Iceland. Some lines of evidence suggest that the gradual birch decline could be a result of reworking of soil pollen, but independent evidence suggests that this may not necessarily be the case. The pollen record indicates that birch woodland was replaced by acidophilic taxa (notably Empetrum nigrum and Sphagnum), again contrasting with the more usual pattern of Poaceae expansion seen in post-landnam pollen diagrams from mires close to farm sites. Chironomid and Pediastrum accumulation data show that the limnic environment became more productive immediately after landnam, probably because or anthropogenic disturbance. An increase in sedimentation rate after landnam appears initially to have been caused by increased lake productivity, while reworked inorganic soil materials became a significant contributor to the sediments after c. AD 1200. The data suggest that the impact of settlement on terrestrial vegetation may have been more variable than previously thought, while freshwater ecosystems experienced significant and rapid change.