HYDROMAN: Impacts of hydrological changes versus human activity on Central-West African forests during the Holocene

• Applicant: Dr. Yannick Garcin
• Subject Area: Palaeontology ; Mineralogy, Petrology and Geochemistry
• Term: from 2013 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 234368558

Central-West Africa hosts the second largest contiguous expanse of moist tropical forest in the world, which is currently under severe threat of humans through deforestation and forest fires. To understand the underlying processes controlling changes within tropical forests of Africa, it is important to determine the drivers responsible for the past forest disturbances. During the Holocene (the last 11,500 years) those tropical forests underwent alternating periods of expansion and contraction, driven by climate variability, although during the last ~3000 years human activity associated with the spread of the Bantu-speaking people may have had an additional effect. However, the existence of marked episodes of human disturbances in the past remains highly ambiguous. To resolve the drivers and mechanisms, which have affected the Central-West African forests during the Holocene, I propose to analyze novel climate-proxies directly recording changes in the hydrological cycle in combination with vegetation-proxies and indicators of anthropogenic disturbances. I will use molecular-based proxies, particularly, compound-specific hydrogen and carbon isotope ratios, on lake-sediment cores from Cameroon. I will apply a newly developed regional transfer function of sedimentary lipid biomarker hydrogen isotope values, which were found to accurately record the modern variability in the hydrological cycle. Changes in vegetation composition (e.g., C3 versus C4 plants) will be estimated using lipid biomarker carbon isotope values while past anthropogenic disturbances will be identified by combining X-ray fluorescence scanning and specific organic tracers for agricultural activities, erosion, and biomass burning. This complete dataset will allow constructing a robust paleo-environmental framework to ultimately test the role of climate change and human activity on the evolution of forests in Central-West Africa during the Holocene. The findings of how these drivers affected the structure and composition of past tropical forests will help to predict how future global changes would affect the present forests in the region.

• DFG Programme: Research Grants