Cape Town - The devastating fires that ripped through Knysna in June 2017 have not been forgotten as a new paper analysing the fire event concluded that they formed South Africa’s largest wildland fire disaster in terms of the number of structures lost and economic losses – and that such fires would become increasingly more common.
Local Cape researchers who conducted the study found that the annual maximum fire weather risk approximately doubled in the last 35 years and that more fires of this nature could be expected in the future.
The paper was 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: “Wildland-Urban Interface (WUI) fires are becoming more and more common globally, this is due to, among others, population growth, people wanting to live near natural areas, climate change and fuel build-up.
“Even though these events occur all over the world, most research has been done in the US and Australia. 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.”
By analysing this fire, Flores-Quiroz said 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.
If the situation continued like this, Flores-Quiroz said more and 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 fires disaster and found that both the severe medium-term regional drought and the weather conditions severely hampered fire suppression.
Stefaan Conradie, a contributing author from UCT, 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. 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,” Conradie said.
Conradie said along the South Coast, the highest fire danger weather tended to occur in winter and spring, not summer and autumn as in Cape Town, which illustrated a lack of distinct fire season in the Knysna-Plett region of the Western Cape.