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Monday, June 23, 2014

Fires and grass burnng in Kruger National Park

People are always very curious and horrified that in places like Kruger National Park controlled burning takes place and want to know why it is done. While in Skakuza, I contacted the Biodiversity Conservation Manager / Fire Protection Officer and this is their official release on the necessity of burning. The opposite side of the road is always left unburned and the difference can be seen in the last picture.
It does not take long for the animals to return to burnt areas to enjoy the new shoots sprouting out.
What are bush (veld) fires about and how necessary are they in the park?

African savannas have evolved with fire over thousands of years and veld (or bush) fires are very common in these savannas, especially in the dry season. Without fire, the vegetation and animal life of savannas would consequently be very different to what it is.
In Kruger being a savannah system; the fire season generally is between May and October, with most fires being set in July -September. Fires in Kruger are managed according to the ‘patch mosaic’ fire policy. In brief, the percentage of the Park which is burnt annually is dependent on the total rainfall received during the preceding two years and the objective of fire within the section.
 Research has also shown that the greater the rainfall, the greater the grass production and the greater the area which consequently burns every year. This relationship is consequently used to calculate an annual quota of how much needs to be burnt. At the end of the summer season, firebreaks are graded or burnt around the perimeter of the park and the infra-structure.

As soon as the grass is dry enough to burn, rangers apply controlled burns in their sections early in the fire season when the grass is still partly green thereby resulting in a patchy burn, i.e. some grass is not burnt, or is poorly burnt, whilst in other areas, all grass is burnt. This results in variable fire effects, which in turn have variable effects on a very wide spectrum of organisms.  Ignition is usually at a single point, the idea being to imitate how nature does this i.e. a lightening strike.
 Another objective of this approach is to reduce the amount of grass, thereby reducing the likelihood and extent of high-intensity fires later in the season. The burns are monitored by means of satellite images (MODIS– Moderate Resolution Imaging Spectro-radiometer) and information provided by the rangers. Management burning normally stops at the end of July, when the risks of a high-intensity fire, or an uncontrollable fire, increases considerably. Later in the season (October to November) lightning fires may occur.

Twice a day during the fire season, the rangers receive a weather and ‘Fire Danger Index’ (FDI) reports via e-mail from the Fire Protection Association’s Fire Protection Officer (FPO) in Skukuza. The FDI is determined by using a number of weather criteria to calculate the risk or likelihood of a fire running out of control. The index ranges from ‘Safe’ to ‘Extremely Dangerous’ conditions, when no fires may be lit, except for the purposes of cooking. It is often cooking fires which result in runaway fires, so please take care when making a braai fire!
Regardless of their cause, unscheduled fires occur every year, especially from September onwards, when conditions are hot and very dry. Most of these fires are ‘jump’ fires; fires which jump over the firebreaks under strong wind conditions and result in high-intensity burns. Some of these jump fires originate in Mozambique while others are caused by careless tourists who throw burning cigarettes from their vehicles. Poachers sometimes burn the veld intentionally to lure animals onto the resulting green lush, and people walking through the park illegally from Mozambique and over-nighting in the veld light fires which can spread the next day.

Contrary to what some people believe, veld fires very seldom permanently destroy the vegetation in a savanna.
Perennial grasses which appear to have been destroyed completely re-sprout from their basal parts the following season; while the annual grasses survive fire by dropping their seeds early in the season, with fire having practically no effect on them or the soil surface.

Woody plants, especially bushes, often get burnt down to ground level (but are very seldom killed outright). They re-sprout again during the next rainy season. Being taller, savanna trees also have thick bark for protection and are little affected by fire, except perhaps to have their lower branches scorched, during fire. But they are very seldom killed. Fire consequently has the effect of keeping the veld more open, which in turn favours certain animal species and is also beneficial to visitors as it provides greater visibility.
 
Is there impact of fires on animals?
Another misconception is that fire kills almost every animal in its path. Remember that savanna animals have evolved with fire over thousands of years and are therefore very successful in surviving fire. Although some do get killed in fire, but by far the greatest majority survive a fire. Animals can sense fire when it is still very far away and most normally have enough time to escape or move out of the path of fire front.
Reptiles and many kinds of smaller mammals and insects escape into holes in the ground or in logs, tree-trunks and under rocks, etc. where they are safe, because the heat from the fire front seldom penetrates the soil below 5 cm in depth. These individuals consequently re-colonize a burnt area very quickly after fire.

All fires are monitored by our rangers. After fire, rangers will record co-ordinates and other information on the fire and send this to the FPO. This information is used for a variety of management and research purposes.
Thank you Nick for this wonderful insight into burning.

2 comments:

Jonker Fourie said...

In some areas fires are needed for rejuvenation. I'm thinking of places where fynbos occur. Around here we had a huge fire a few years ago and it destroyed all the exotics, allowing the indigenous grasses to take hold again.

Gaelyn said...

We may not like to see char or deal with smoke but fire plays such an important role in environments. Great piece Joan.