Fire History of Lake Tanganyika (Mahale Coast) Watersheds Reconstructed
from Macrocharcoal Records
Abstract
Lake Tanganyika, located in central East Africa, is the longest and
second deepest freshwater lake on Earth. Lake Tanganyika’s diverse
ecosystem and watershed are under threat today by human activities from
extensive deforestation, climate change, and human-induced fires.
Therefore, documenting fire and deforestation history in Lake
Tanganyika’s surrounding watersheds is crucial for improving watershed
management around the lake in the future. Analyzing sediment charcoal
records from sediment cores provides high-resolution paleolimnological
evidence that reflects the timing and impacts of fire histories and
landscape conversion. Macrocharcoal, an incompletely combusted residue
that remains when plants materials were burnt by fire, can be
transported away from the fire sites and deposited into the lake. We
sampled and calculated macro-charcoal (>61 μm) sediment
flux from three sediment cores, LT-98-20MR, LT-98-15M, and TANG14-1MC-1A
from the lake’s east-central coast. 20MR and 15M are 2.4 km apart,
whereas 1A and 15M are 6.97 km apart. We have also compared our results
with several previously studied cores from the central part of the lake.
Core 15M, which is closest to the shore and has the highest
sedimentation rates, showed peaks of charcoal flux from 1830 – 1850,
1896, 1910 – 1914 and 1996 AD based on correlation with a nearby core.
Core 20MR, which is further offshore than 15M, has multiple sharp
charcoal flux peaks at 1674, 1770, 1848 and 1881 AD, again using
correlation with a nearby core. Core 1A, where the watershed has been
intensively managed at Kalilani Bay in recent decades (McGlue et al.,
2021), shows two significant peaks at 1668 and 1808 AD. The difference
in timing of the distributions of sediment charcoal flux peaks from our
study indicates these charcoal histories record localized wildfires.
Some of these may correlate with the late Little Ice Age dry period in
the late 18th – mid 19th C, whereas other more recent ones maybe linked
to human activities such as land clearance for cassava cultivation. Low
fire frequencies at most sites during the late 19th – mid 20th C may
correspond to reduced human populations and disease outbreaks during
that period.