Archaeological and palynological evidence of iron smelting and its ecological consequences in the Ijebu Forest, Nigeria

This study examines the use of wood resources for iron smelting and the impact of this on the forest and woodland resources of Odonoko-Odoroga in the Ijebu-Ode region of southwest Nigeria. Pollen analyses were conducted on sediments from an archaeological unit and a sediment core within the site of Odonoko-Odoroga. Before c. cal. AD 1435–1490, the environment was characterised by a vegetation complex of freshwater swamp and rainforests. After this period, iron smelting began in the community, indicated by the recovery of abundant iron slags from the archaeological context. The environment was transformed into a more open landscape with secondary forest and freshwater swamp forest trees being dominant. Several of the freshwater swamp forest tree species are associated with iron smelting in Yoruba traditions. Subsequently, as cultural materials (and iron slags in particular) drastically decreased, the majority of the freshwater swamp forest taxa also declined. In contrast, herbaceous plants, weeds and fungi associated with farming, animal husbandry and soil erosion increased significantly. These changes coincided with a shift from an iron-smelting society to one dominated by farming.