Human impact on an island ecosystem : pollen data from Sandoy, Faroe Islands.

Aim: To investigate the form and dynamics of ecosystems on an isolated island in the North Atlantic before human settlement in the first millennium ad, and the effects of human activities thereafter. Location: The island of Sandoy, Faroes (6150¢ N, 645¢ W). Methods: Two sequences of lake sediments and one of peat were studied using pollen analysis and sedimentological techniques. Age models were constructed on the basis of radiocarbon dating and, in one case, tephrochronology. The data were analysed statistically and compared with existing data from the region. Results: The pollen data indicate that early Holocene vegetation consisted of fell-field communities probably growing on raw, skeletal soils. These communities gave way to grass- and sedge-dominated communities, which in turn were largely replaced by dwarf shrub-dominated blanket mire communities well before the first arrival of humans. There is evidence for episodic soil erosion, particularly in the uplands. Changes in the records attributable to human impact are minor in comparison with many other situations in the North Atlantic margins, and with certain published sequences from elsewhere in the Faroes. They include: (1) the appearance of cereal pollen and charcoal, (2) an expansion of ruderal taxa, (3) a decline in certain taxa, notably Juniperus communis and Filipendula ulmaria, and (4) a renewed increase in rates of upland soil erosion. The reliability of palaeoecological inferences drawn from these sites, and more generally from sites in similar unforested situations, is discussed. Main conclusions: The subdued amplitude of palynological and sedimentological responses to settlement at these sites can be explained partly in terms of their location and partly in terms of the sensitivity of different parts of the ecosystem to human activities. This study is important in establishing that the imposition of people on the pristine environment of Sandoy, while far from negligible, especially in the immediate vicinity of early farms and at high altitudes, had relatively little ecological impact in many parts of the landscape