An assessment of climate, weather, and fuel factors influencing a large, destructive wildfire in the Knysna region, South Africa
Date
2018-08-30
Journal Title
Journal ISSN
Volume Title
Publisher
SpringerOpen
Abstract
Background: In June 2017, wildfires burned 15 000 ha around the town of Knysna in the Western Cape, destroying
> 800 buildings, > 5000 ha of forest plantations, and claiming the lives of seven people. We examined the factors
that contributed to making this one of the worst fires on record in the region.
Results: One third of the area that burned was in natural vegetation (mainly fynbos shrublands), and more than
half was in plantations of invasive alien (non-native) pine trees, or in natural vegetation invaded by alien trees. We
used satellite imagery to assess burn severity in different land cover types by comparing pre- and post-fire images
to estimate biomass consumed. We used daily weather data from two weather stations to calculate fire danger
and drought indices over 70 years, and compared the fire weather conditions during the 2017 Knysna fires to the
long-term weather record. The amount of biomass consumed was significantly higher in plantations of invasive
alien trees, and in fynbos invaded by alien trees, than in uninvaded fynbos, providing support for the contention
that invasion by alien trees increases the impact and difficulty of control of wildfires. Fire danger indices on the
days of the fires were in the top 0.1 to 0.2% of days in the historic record, indicating that fire weather conditions
were extreme but not unprecedented. The fires were preceded by a prolonged drought, and 18-month running
means for two drought indices were the highest on record.
Conclusion: The severity of the fires was exacerbated by very high fire danger conditions, preceded by an
unprecedented drought, and further worsened by the conversion of natural fynbos vegetation to plantations,
and invasion of vegetation by alien trees. Historical fire suppression also resulted in fuel buildups, further aggravating the
problem of fire control, while residential development within and adjacent to fire-prone areas increased the risks faced by
residents. Our results support calls to control invasive alien plants, reduce commercial planting of invasive alien trees,
strictly regulate development in areas of high fire risk, and maintain awareness of the need for fire-wise practic.
Description
CITATION: Kraaij, T., et al. 2018. An assessment of climate, weather, and fuel factors influencing a large, destructive wildfire in the Knysna region, South Africa. Fire Ecology, 14:4, doi:10.1186/s42408-018-0001-0.
The original publication is available at https://fireecology.springeropen.com
The original publication is available at https://fireecology.springeropen.com
Keywords
Droughts, Wildfires--Climatic factors, Wildfires
Citation
Kraaij, T., et al. 2018. An assessment of climate, weather, and fuel factors influencing a large, destructive wildfire in the Knysna region, South Africa. Fire Ecology, 14:4, doi:10.1186/s42408-018-0001-0