Veld Fires

Fires have been a regular feature of the African veld ever since grasses evolved 20 million years ago. Originally lightning would have been the cause, but more recently man has seen the benefits of fire and is the main agent.

Grass itself improves when correctly burnt. As winter – the dry season – approaches, grasses must shut down activities, so transfer any valuable minerals down to the roots for storage and later recycling. The aerial portion dries out as it is abandoned, and, without minerals, becomes useless to grazers. Unless burnt it shades out next spring’s new growth. Grass that is never burnt loses vigour and supports no wildlife at all.

Long dry grass also shades out nearly everything else. The wealth of beautiful flowers for which the Drakensberg is famed, many of them endemics, depend upon fire. Without it the smaller species would never see the sun, and most of these erupt through the blackened landscape with the first rain, and sometimes even before it. Their reproductive cycle must be complete before tall grasses form shade. Proteas must have fire to germinate. Once it was thought that heat stimulated dormant seeds – as it does for some other species – but smoke is the vital agent.

Fire rarely kills the trees growing in open veld. These are species that are too small to compete for light in the forest, so must withstand fire. They do so with thick corky bark that insulates the trunk. Grassland animals all have a way of surviving fire. Bigger animals can easily keep ahead of advancing flames; smaller species retreat down burrows; some insects get burnt, but never all. It is these fried snacks that attract birds to burns even before they have stopped smoking.

At the Cavern fire is controlled using firebreaks. These can be seen as broad stripes across the landscape. They are burnt very carefully, all hands in attendance, on windless days, so the fire cannot escape. Firebreaks cannot burn again, even with fresh green growth, so bigger fires cannot cross them. Enclosed blocks can then be burnt when necessary, usually as a mosaic in a two-year cycle. Most animals forage in blocks of younger grass, while many nest or hide in the older grass.

David Johnson

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