Alien Clearing and Fire Management

Extreme weather events, such as the heat waves that have spread across the Western Cape this summer, are a feature of climate change. These events lead to a more severe and longer fire season and this in turn will lead to more frequent and larger veld fires.

Invasive woody alien plant species introduced to the Fynbos biome have a detrimental impact on fire safety, water production and biodiversity in the region. These invasive alien vegetation species originate from fire-prone environments and their ecology is intrinsically linked to fire. Frequent and large veldfire events in the Fynbos biome have enabled these plants to infest vast tracts of the natural landscape, which in turn has contributed to increases in the frequency and intensity of fire events. The risk is expected to be exacerbated by climate change, which could cause larger and more frequent fires– and unless we develop a greater understanding of how to manage wildfire, it will become increasingly difficult to reduce the damage to people, the economy and the environment. Recent big runaway fires in the Western Cape have reignited the debate about unplanned and unmanaged wildfire, and how much of a threat it is to the preservation of plants, some of which most likely will never recover if the fynbos burns too frequently. Not often mentioned is the threat that unmanaged wildfire also poses to wildlife – including birds, which depend on healthy fynbos for their survival. Historically, wildfire management has been heavily dependent on suppressing un-managed fire and pre-emptive, planned burning.

Recently, more sophisticated tools to help fire management have become available, as have advances in fire modelling and improved fire weather prediction. There is consensus now that fynbos needs fire, which can be an agent of rebirth or an inferno of destruction – the question is how frequent and how hot. If fynbos is burnt every seven to twenty years, aging plants are killed off, many kinds of seeds burst into life and bulbs start to grow again. “Without fire, there would be no fynbos – it’s as simple as that,” says Dr Brian van Wilgen of Stellenbosch University’s Centre for Invasion Biology. However, it’s not altogether so simple. Different species of fynbos plants are favoured by fires of different frequencies within the range of about seven to twenty years. If fires come too soon and too frequently, or too seldom, then some species may be eliminated. Dr Tony Rebelo of SANBI suggests that fires in veld over 25 years old, or due for a burn with-in two years, should be allowed to run. However, he points out that it has not been established who would make such a decision or which risk factors should be considered. One problem with this, is that many of these areas are infested with invasive alien vegetation. These “fuel loads” can lead to greater intensity of fires, with negative consequences for indigenous seed banks. Moreover, this can also lead to a mass germination of invasive alien plant seedlings. If the dexterity is not in place to deal with the follow-up clearing of these invasives, it can lead to massive additional clearing costs at a later stage, and many very negative ecosystem service impacts, such as water loss, biodiversity loss, an impact on the productivity of land and much more – ironically including the likelihood of worse fires in years to come. While this complex debate continues, there appears to be agreement on a single under-lying principle: fires should be managed. Steps in this direction are already happening. Critical scientific data about climate change is being gathered, wildfire behaviour is being monitored, and the formation of Fire Protection Associations is being encouraged to help landowners work together to practice Integrated Fire Management. Importantly, the project is encouraging experts from a wide range of related disciplines to research their work together and encourage open public debate with the aim of avoiding the threat of destructive fires wreaking irreversible damage to the people, homes, the economy and the environment.