Anthropology Fall 2024 Colloquium Speaker Series

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 Stella Mosher, Ph.D.

 

"Fire in the Fynbos: late Holocene paleofire and linkages among climate, vegetation, and people in South Africa’s Cape Floristic Region"

 

Thursday, November 7, 2024

 

 

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*Seating is limited

"Fire in the Fynbos: late Holocene paleofire and linkages among climate, vegetation, and people in South Africa’s Cape Floristic Region"

Abstract:

Fire is an important disturbance in many of Earth’s ecosystems, including South Africa’s Cape Floristic Region (CFR), a Mediterranean, fire-adapted biodiversity hotspot of global significance. However, most paleoecological studies in the CFR lack the temporal resolution to adequately address shifts in discrete events, such as fire, over long timescales and alongside variability in climate, vegetation, and anthropogenic impacts. The CFR is recognized to include a range of hydroclimate regimes varying in seasonality and moisture source, and a long history of human activity. In particular, pastoralist herders arrived in the region ~2,000 years ago and are suspected of burning the landscape to facilitate fresh forage for their livestock, possibly resulting in fundamental alterations to fire activity in the region. This project uses high-resolution sedimentary charcoal reconstructions from lacustrine archives to quantify the impacts of climate change and human activity on fire over the past 4200 years using two coastal, ecotonal CFR lakes: (i) Verlorenvlei – along South Africa’s west coast, experiencing seasonal, winter rainfall, and (ii) Eilandvlei – along the southern Cape coast, experiencing aseasonal, year-round rainfall. At both sites, moisture availability is a key determinant of variability in fire, out-weighing human impacts on millennial timescales. But the sites respond differently to changes in moisture, highlighting the significance of climate-fuel dynamics, and with implications for ecosystem resilience under changing climate and anthropogenic pressures. Next, this project reconstructs fire frequency, measured as fire return intervals (FRIs), from Eilandvlei over the last 4200 years. This tests the extent to which our historical, ecological understanding of FRIs, with 10 – 20 years between burns, is maintained over time and through periods of climate and vegetation change. These results reveal a range of FRIs – between 10.5 and 166 years, suggesting that our historical, ecological perspective fails to capture the full range of natural variability experienced at Eilandvlei over millennia. The long-term paleofire reconstructions presented in this project refine our understanding of fire activity and ecosystem responses to natural and anthropogenic influences on millennial timescales and offer valuable context for management and conservation efforts seeking to preserve the unique biodiversity of the CFR.