An analysis of selected influencing factors of wildfire regimes over the last three decades in the Boland Mountain Complex, South Africa

Ethical ref #: 207003831/06/2020

This study examined the influencing factors of wildfire regimes in the Boland Mountain Complex (BMC), South Africa, over thirty years. The fynbos region, covering the BMC, is one of the world’s six floral kingdoms with high levels of endemism and is both fire-adapted and fire-dependent. Inappropriate fire regimes are a major concern for biodiversity loss and as such it is important to understand the influencing factors to facilitate decision making. This study aims to identify and analyse the key anthropogenic, environmental and climatic factors contributing to wildfire frequency, size, seasonality and fire return intervals over time. Utilizing a comprehensive dataset that comprises of fire records inclusive of global position information, satellite imagery, land use data and meteorological records a mixed-methods approach was employed to evaluate various relationships. The results show both an increase in fire frequency and cumulative hectares burnt per year. The cumulative hectares has a very highly significant statistical link to both the number of Very Large and Large category fires. This highlights the importance of speed and scale of the suppression response. These increases could be due or partly due to reporting bias or urban expansion. The fire return period from a space-time composite perspective has an average fire return interval of 8. 63 years which is currently not conducive to maximise biodiversity. Ignition frequency was looked at in relation to the closest town and transport route, with Grabouw and Track Footpaths having the highest frequency. The hectares burnt for each Very Large category fire has a very highly significant statistical link to biomass and total hectares burnt in the BMC. None of the weather related variables showed any notable links between the dependant variable of total hectares burnt per Very Large fire category. This could be due to distance from weather stations and variations in microclimates within mountainous areas. There is however a notable link between antecedent annual rainfall and the fire frequency and cumulative hectares burnt in the BMC for the same year. Results from this research show an overall trend of an increase in fires highlighting key risks and certain geographical areas as hotspots. This can be used to motivate for additional funding, prioritise resources and advise for best land use practises. There is also a number of recommendations for future research to provide improved results and limit bias.