During the first millennium ad, Germany, like other European regions, witnessed dynamic interactions between human populations and the environment, resulting in effects on landscapes and vegetation. Despite their significance, the detailed changes and links between vegetation and population dynamics in Germany during this period are not yet fully understood. This study addresses this gap in an interdisciplinary approach combining high resolution pollen analysis, varve counts and AMS radiocarbon dating on a partially annually laminated lake sediment core from Kleiner Tornowsee, in Brandenburg, north-eastern Germany. Archaeological evidence of the region and available pollen data from another lake, Sacrower See, also in Brandenburg, were used for comparison and allowed the identification of regional developments. The results suggest that the Germanic tribes living there during the Roman Iron Age (ca. ad 1–375) were adept at maintaining an economy based on crop growing and the keeping of livestock. During the Migration period (ad 375–600) there was a relatively slow but continuous expansion of woodland, coinciding with two phases of depopulation. A low but constant presence of indicators of human activity in the pollen profiles, however, suggests that these areas were not completely abandoned. Evidence for an early phase of human activities starting again in the late 6th or early 7th century ad at both sites is striking, because of a lack of archaeological evidence for any settlements in this period. During the High Middle Ages (ad 1000–1300), a further increase in farming activities resulted in intensified clearance of woodland for farmland and led to more crop growing than grazing in the 11th and 12th centuries.