Paleoecological Reconstruction of Vegetation and Climate Change in the Lake Chad Basin Over the Last 10,000 Years Using Pollen and Isotope Proxies

Understanding long-term vegetation and climate dynamics in the Lake Chad Basin requires integration of multiple paleoecological proxies to overcome the limitations of individual methods. This study reconstructs vegetation cover and climate variability over the past 10,000 years using pollen assemblages, stable isotopes of carbon-13 and oxygen-18 from organic sediment fractions, and phytolith records extracted from dated lake sediment cores retrieved from three sites in the Nigerian sector of the Lake Chad Basin. Sediment cores were dated using accelerator mass spectrometry radiocarbon dating and optically stimulated luminescence methods. Pollen assemblages were analysed using constrained cluster analysis and ordination to identify vegetation zones and transitions. Isotope records were interpreted using published calibration datasets for the West African Sahel. Results reveal a dynamic vegetation history characterised by an African Humid Period from approximately 11,000 to 5,500 years before present, during which lake levels were substantially higher and vegetation was more densely wooded than today, followed by progressive aridification and southward retreat of Sahelian vegetation. Abrupt vegetation transitions at 8,200, 5,500, and 4,000 years before present corresponded to globally recognised climate events. The paleoecological record demonstrates that current vegetation degradation, while exacerbated by human pressure, is superimposed on a long-term drying trajectory. These findings provide critical baseline context for interpreting contemporary ecological change and modelling future scenarios for the Lake Chad Basin under climate projections. Keywords: paleoecology, Lake Chad, pollen analysis, climate reconstruction, Holocene.