Waja

Orijemie, Emuobosa Akpo
Department of Archaeology and Anthropology,
University of Ibadan, Ibadan, Nigeria
Email: [email protected];
[email protected]
86

Abstract
The pollen records of two terrestrial cores Ahanve (Badagry) and Ogudu (Lagos) in
the freshwater, and mangrove swamp forest (MSF) zones respectively of southwest
Nigeria provide evidence of changes in ecology and species diversity of the MSF
and the adjoining lowland rainforest (LRF) during the Late Holocene. At ca. 3109 ±
26 yrs BP in Ahanve and at as yet an unknown time in Ogudu, Rhizophora spp. and
other mangrove species declined significantly. Though Rhizophora spp. recovered
quickly at Ogudu, they completely disappeared from Ahanve and are absent from
there today. Similarly the LRF, which hitherto was abundant and quite diverse at
Ahanve decreased and was replaced by secondary forest and coastal savannas. On
the other hand, the LRF increased sharply at Ogudu with relics of it still remaining
there at present. Species diversity of the LRF at Ahanve during and after the major
vegetation change that took place became very low whilst most species
disappeared. In contrast, at Ogudu the LRF remained despite deteriorating
conditions and was initially diverse. Its subsequent decline in species composition,
which was recorded towards the top of the core, is regarded as a recent development
as revealed by both the pollen record and charcoal analysis. The contrasts in the
species diversity of the LRF at both sites seem to underscore the intensity and
impact of humans at Ahanve and Ogudu.
Key words: Tropical rainforests, Vegetation change, Rhizophora spp., Human
impact