Danish forest development during the last 3000 years reconstructed from regional pollen data

Most present Danish forest types are a direct result of recent silvicultural practice. We use fossil pollen data converted into estimates of tree abundance to map the development of forest types during the last 3000 radiocarbon yr. The forest types were clusters in an artificial neural network based on all available European Holocene pollen data. Diverse deciduous forest types found 3000 yr ago were: replaced by less diverse Fagus-dominated types over a period of 2000 yr. The present day map contained many new combinations of tree species, dominated by Picea and Pinus. The association between the increase in non-forest communities and establishment of Fagus suggests that anthropogenic activity has accelerated the loss of species-rich deciduous forest with abundant Alnus, Corylus, Quercus and Tilia. We conclude that the natural forest composition of Denmark would be deciduous forest today with a significant presence of Fagus sylvatica. Recent forest development has created a break in compositional continuity with the past that is unnatural and has posed problems for forest-dependent biota.