THE IMPACT OF 6,000 YEARS OF AGRICULTURE ON DANISH LAKES: EXAMPLES FROM PALAEOECOLOGICAL STUDIES

The impact of human activities on terrestrial biota during the Holocene has been a major focus of palaeoecological research in Europe but the concomitant effects on lake ecosystems have been given less attention. A multi-disciplinary study of the sediment record from Dallund Sø, a lake on the island of Funen, Denmark, was carried out to investigate lake response (inferred from diatom, zooplankton, macrophyte and Pediastrum remains) to terrestrial change (inferred from pollen data and soil erosion history) in the heavily-modified cultural landscape of Denmark. The effects of changing land-use since the introduction of agriculture ca. 6,000 years ago are reflected in the sediment record and the impact of human activities on both land and lake was clearly dramatic. Moderate nutrient enrichment of the lake was inferred during the Bronze Age (1700 to 500 BC) and Iron Age (500 BC to 1050 AD) periods following the deforestation of the catchment. A marked eutrophication of the lake was associated with major changes in agriculture during the Medieval period (1050 to 1536 AD) and continued to the present day. Preliminary data from other sites suggest that many lakes in Denmark may have been impacted by human activities over similarly long timescales.