LATE HOLOCENE FIRE HISTORY OF THE WATERSHED OF LAKE TANGANYIKA (MAHALE COAST) RECONSTRUCTED FROM MACROCHARCOAL RECORDS

Abstract

Fire in semi humid regions of tropical Africa is driven by random lighting strikes and intentional anthropogenic burnings for charcoal production, which often result uncontrolled fire that causes landscape conversion. However, the relative contributions of localized and strictly human-caused fire vs. more regional burning facilitated by climate events in late Holocene African fire history needs to be clarified. In this study I have investigated the history and drivers of the late Holocene fire, a region in central eastern Africa adjacent to Lake Tanganyika. I have taken a paleolimnological approach, studying sedimented macrocharcoal preserved in sediment cores, to obtain a record of macrocharcoal concentrations and fluxes spanning the last ~ 500 years. I compared macrocharcoal concentrations and flux patterns with lake level and lake temperature changes for nine dated sediment cores (18M, 15M, 20MR, 25M, 21MR, 1A, KH1, 2A, and 6A) collected from nearshore east central coastal areas and southeastern basin locations. From 1500 to 2000 C.E., fires that are recorded in the cores near the northern Mahale area (the east central part of the lake where the majority of records were located) were mostly uncorrelated and presumably represent very localized fires. Only a few events are recorded in multiple cores and thus seem likely to be related to climatic drivers, such as in the late 17th century, a dry period during the Little Ice Age and or during the mid-19th century. Low fire frequencies observed during the late 20th century are possibly related to prior extensive deforestation in the study area. However, the dominance of uncorrelated late Holocene charcoal records near the Mahale area suggests that most of these fires were highly localized and likely human set (for land clearance or charcoal production) rather than being driven by regional climate events.