Iron Age landscape changes in the Benoué River Valley, Cameroon

The introduction of agriculture is known to have profoundly affected the ecological complexion of landscapes. In this study, a rapid transition from C 3 to C 4 vegetation is inferred from a shift to higher stable carbon ( 13 C/ 12 C) isotope ratios of soils and sediments in the Benoue River Valley and upland Fali Mountains in northern Cameroon. Landscape change is viewed from the perspective of two settlement mounds and adjacent floodplains, as well as a rock terrace agricultural field dating from 1100 cal yr BP to the recent past ( 15 N/ 14 N) isotope ratios and soil micromorphology demonstrate variable uses of land adjacent to the mound sites. These results indicate that Early Iron Age settlement practices involved exploitation of C 3 plants on soils with low δ 15 N values, indicating wetter soils. Conversely, from the Late Iron Age (>700 cal yr BP) until recent times, high soil and sediment δ 13 C and δ 15 N values reflect more C 4 biomass and anthropogenic organic matter in open, dry environments. The results suggest that Iron Age settlement practices profoundly changed landscapes in this part of West Africa through land clearance and/or utilization of C 4 plants.