The use of fire in a reserve is always a contentious issue because people often don’t realize the importance of fire as a management tool and are always concerned about the wildlife, especially the small animals that cannot escape it – or have they evolved ways to protect themselves?
In this post I will be referring to planned fires, arson and run-away fires are a different thing completely. On a reserve there are two main types of fires; firebreaks and block burns. Firebreaks are normally strips that are burned along a road or some other natural barrier; river courses, forests etc. Along road edges they perform two main functions; they act as a barrier to prevent accidental fires lighting from careless people discarding matches etc from a vehicle’s window and they act as a starting point for a ‘back-burn’. To stop a raging veld (grassland) fire is an almost impossible task without a firebreak which functions as follows. When a fire is detected heading in a specific direction a back burn is immediately started along the firebreak. This fire will then burn ‘backwards’ or towards the veld fire thereby burning off any grass that would act as fuel for the run-away fire. When these two meet the fire simply burns itself out as there is no more fuel left to burn.
A block-burn is a very different fire and has a completely different purpose. The veld or grasslands in South African needs to be burned periodically in-order to prevent them becoming moribund which inhibits the germination of seeds due to too much shade and/or too much competition. (In some biomes it has been found that if grasslands are not burned within seven years some of the ‘weaker’ species of grass become extinct). Grassland scientists have calculated that veld should be burned every three to four years. All reserves have (or should) a fire management burning policy which divides the reserve up into ‘blocks’ which are burned every three or four years. These blocks are set out in a ‘mosaic’ ensuring that there is always unburned veld scattered throughout the reserve. Firebreaks are used extensively around blocks that are to be burned.
To add further to the intricacy of block burns is the temperature that the fire should be burned at. Reserve managers can do ‘hot’ burns or ‘cool’ burns depending on the desired results. Hot burns will be done when the objective is to control the invasion of scrub and invader species. To do a ‘hot’ burn managers will burn later in the day when there is no dew and they have a slight breeze. Fires will be put in ‘against’ the breeze so that the fire burns very slowly and thoroughly. If a ‘cool’ fire is needed they will burn earlier and burn with the breeze so that the fire covers the area quickly. In a hilly terrain hot fires will be burned down the slope and cool fires up the slope.
As stated above, fire management seems pretty straight forward – but it is not! The fire creates its own wind, the wind is constantly changing and the smoke makes visibility impossible, a critical factor as most run-away fires flare up behind the burn.
Lets very briefly look at the animals and how do they cope with fire – bearing in mind that fire has been around forever ignited by lightning or falling rocks etc. To my mind the most vulnerable animals to fire are tortoises as they are slow moving and live above ground but they never live in areas that are 100% grass. They live in drier areas where there are large open areas of soil or rocks with no vegetation. As soon as they smell smoke they head for these areas and partially bury themselves. Fire does occasionally catch them and I have seen a few with evidence of burns but they seem to cope quite well with no apparent ill effects. Snakes, one would presume, would also be vulnerable to fire but they are not as they quickly dive down the nearest available hole, climb a tree or find a stream. What about the insects? Most grassland species either live in holes or are able to fly so no major problem there! Rats and mice are hole-dwellers so they simply hide until the fire has passed. What about the bigger animals like antelope etc? They are fleet-of foot so they can easily outrun a fire, either away from it or in some cases through it, something that I have had to do on numerous occasions during my many years of burning experience. I have burned fire breaks and block burns for 25+ years and the ONLY animal that I ever found burned was one snake.
The most important concern with block burns is to NEVER encircle an area which will trap the animals in the middle; one must always burn from one side to the other.
Please bear in mind that the above refers to controlled burns – arson or run-away fires are totally different and many animals (and people) have been killed by this type of fire. Why should it be any different? Controlled fires are done when the conditions are right and the fires movements are predictable. Runaway fires often encircle an area offering no escape route and ignited in the worst possible conditions!
My final comment is that legally block burns may only be done in spring after 25 mm (1 inch) of rain has fallen.
Nigel Anderson – Guide for African Insight
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