Understanding the Primary Controls on Afroalpine Wildfire Regimes Based on Charcoal Records from the Rwenzori Mountains

The high-elevation alpine ecosystems of equatorial Africa have traditionally been considered to exist in a climate that is too cool and wet to burn. However, recent extensive fires challenge this assumption, and call into question the controls on fire frequency in these regions. We investigate wildfire regimes in the Rwenzori Mountains of Uganda, a UNESCO world heritage site known for its biodiversity, through the development of sedimentary macrocharcoal records across multiple elevations spanning 12 ka BP to present. We also compare these wildfire records with existing organic geochemical records of temperature and precipitation in the region to assess the climatic, anthropogenic, and ecological controls on Afroalpine fire regimes. Organic geochemical proxy records indicate that the Rwenzori Mountains experienced temperature and precipitation changes consistent with other parts of East Africa, including a ~2-3 degree warming centered at 6 ka BP, and a wetter African Humid Period. Although alpine warming is expected to increase fire frequency, we observe decreased macrocharcoal counts and fluxes in the middle Holocene. Instead, we find peaks in macrocharcoal counts at higher elevations around 12 ka BP, which is likely related to a drier climate at the end of the Younger Dryas and an increase in available fuel due to late deglacial ecosystem succession. Additionally, we find macrocharcoal peaks at all elevations around 2 ka BP, which may be connected to increased human activity and human ignition sources in the mountains. These results suggest that both precipitation and human presence play a role in controlling fire activity in this region. Thus, next steps in fire management must include identifying and regulating human ignition sources in order to prevent extensive fire related damage in the region.