Human–environment interactions in an agricultural landscape: A 1400-yr sediment and pollen record from North Pare, NE Tanzania

Abstract

A sediment and pollen record from the North Pare Mountains in north-eastern Tanzania provides evidence for strong anthropogenic landscape transformations since the 7th century AD and demonstrates that, shortly after the arrival of Early Iron Age farmers, agricultural land use became the main driving force of vegetation and landscape change, predominating over external climatic factors. The absence of pollen characteristic for the corresponding altitudinal submontane forest implies widespread forest clearance and agriculture land use prior to the onset of the sedimentary record. Land clearance, soil erosion, and corresponding accumulation of colluvial slope deposits on the valley floor triggered paludification and the establishment of the Lomwe palaeowetland in the 7th century AD. Accelerated soil erosion and rapid alluvial burial of the palaeowetland between AD1200 and AD1500 represent an environmental tipping point with important repercussions for present day land degradation and resource restraints. Age control is complicated by radiocarbon date reversals and draws on introduced forest taxa Cupressus and Eucalyptus as biostratigraphic markers of the 20th century. Geoarchives from agricultural landscapes that are shaped by long-term settlement and land use, such as the Pare Mountains, can enhance archaeological occupation histories and provide crucial information for both the identification of ecological thresholds and for the reconstruction of environmental transitions during anthropogenic landscape transformations.