Devastating wildfires like those that ripped through Knysna in June 2017 are likely to become more common, according to a new paper analysing South Africa’s largest wildland fire disaster in terms of the number of structures lost and economic losses.
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The analysis was conducted by local Cape researchers, who found that the annual maximum fire weather risk has approximately doubled in the last 35 years, with more fires of this nature expected in the future.
The paper titled “Analysis of the 2017 Knysna fires disaster with emphasis on fire spread, home losses and the influence of vegetation and weather conditions: A South African case study”, by lead author Natalia Flores-Quiroz and others from Stellenbosch, UCT and Vulcan Wildfire Management.
Flores-Quiroz said that wildland-urban interface (WUI) fires are becoming more common globally. This is due, among other factors, to population growth, people wanting to live near natural areas, climate change, and fuel buildup.
“Even though these events occur all over the world, most research has been done in the US and Australia,” she stated. “However, there are many factors that can influence fire spread and home survival. For this reason, it was important for us to study South Africa’s most destructive WUI fire.”
Through this analysis, Flores-Quiroz found that the fire spread was influenced by extreme weather conditions, gale-force winds, high temperatures and low humidity, severe drought conditions, and secondary ignitions due to embers.
The fire was able to jump distances as large as 2.8km.
“WUI fires will continue happening, that is for sure, and not only due to climate change, but we also need to remember that many ecosystems (such as fynbos) need periodic fires.”
“The main issue is that the last decades there has been a strong change in land use, with a growing number of houses constructed in high-risk areas and a large fuel build up (vegetation) due to firefighting operations,” Flores-Quiroz said.
She added that if the situation continued like this, more fires similar to Knysna would be seen, such as the Table Mountain fire in 2021 and the Helderberg fire in 2022.
The team of researchers concluded that several ignitions and severe climatic and meteorological conditions led to the severity of the Knysna fire disaster and found that both the medium-term regional drought and the weather conditions severely hampered fire suppression.
A contributing author from UCT, Stefan Conradie, said this was the first peer-reviewed case study of a South African wildfire that crossed the wildland-urban divide, and it addresses fire spread, damage, and the influence on vegetation, climate and weather.
“Along the South Coast, we found that the annual maximum fire weather risk approximately doubled in the last 35 years,” he stated. “The fire weather conditions on the day were the most extreme on record (1979-2021)”.
“There are indications that houses in areas with dense invasive alien trees surrounding them were at greatest risk of being damaged or destroyed.”
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