Prior to 1995 the forest industry in South Africa was losing about 12 000 ha to fires annually. Post 1995 the average annual losses have increased to 14 000 ha. Last year, as we all know, was a catastrophic year for huge forest fires across the summer rainfall regions of southern Africa.
|A familiar site around Sabie – scorched pine recovering from last year’s inferno.|
“What are we doing about it?” asks KLF’s fire risk manager, Ben Bothma. Landowners are complying with the Veld and Fire Act by preparing “small belts” around an ever-increasing fuel load. “This is a time bomb waiting to go off,” he says.
Ben contends that a “paradign shift” is needed in the forestry industry to address the increasing incidence of destructive fires. “Instead of concentrating on fire belts, all attention should be addressed towards fuel load reduction.”
He says an integrated fire management approach is the solution. Prescribed burning under canopies as well as burning of slash after clearfelling are key components of this approach.
“Fire is part of nature – you cannot keep fires off your land forever. You must manage fire with fire. The Australians have been doing prescribed burns under pine canopies for many years very successfully. In South Africa the Department of Forestry started doing trials way back in 1978, but nothing really came of it,” said Ben.
“Instead of concentrating on fire belts, all attention should be addressed towards fuel load reduction.” Ben Bothma
Now KLF, who lost over 17 400 ha to fire in the Lowveld region last year, have taken the bull by the horns and have opted to follow the prescribed burning approach at a significant scale.
“Since the first rains in November last year we have burnt 7 719 ha under pine, and our target for next year is 20 000 ha,” says Ben. This must be music to the ears of fire experts like Dr Neels de Ronde who has been advocating under-canopy prescribed burning for years.
The burns are carried out under optimum conditions in compartments where the trees are 10 years or older, and only when the temperature is below 23oC Cool, safe burns with low fiame heights are the objective. They are carried out by teams of four to five people who can burn 40 to 50 ha per day.
How effective is this method in reducing wildfires?
Ben maintains that the only compartments that survived the massive fire at Spitskop near Sabie last year were compartments where prescribed burning to reduce fuel loads had taken place.
Obviously there are risks attached to this kind of burning, but Ben has implemented a disciplined control system that works. Weed suppression in compartments to be burnt must be good, while prunings must be kept away from the tree stems. The edges of compartments exposed to the prevailing wind should be burnt two days after a rain, and the rest can be burnt later. Smouldering stumps must be doused in a the same operation.
“Rather be safe than sorry and apply a back-burn for difficult burns.”
Ben has identified a number of “golden rules” to ensure the burns are safe and do not cause damage to the trees (see below).
With the 2008 fire season fast approaching, Ben is confident that their fuel load reduction efforts will pay dividends for KLF.
Golden rules for burning under pine
- Pinus patula and Pinus taeda younger than 12 years not to be burnedPinus elliottii can be burned from 11 years
- Clearfell compartments to be burnt two years before clearfell, because it accelerates the decomposition process
- There is a 1:6 flame to scorch ratio– do not slash weeds before burn as this will increase scorch height
- Steep slopes and difficult topography to be burned either early in the morning or late in the afternoon.
- No burning if temperature is 23 degrees C or higher
- Burning stumps to be doused during the same operation
- Don’t leave pruned branches against tree stems
- Compartment edges exposed to prevailing winds to be burned two days after rains.
Advantages for the forester and the environment
- Reduced cost of fire protection
- Incidence of destructive crown fires reduced
- Narrow fire breaks replaced by broad bands with low fuel loadBurning done under optimum conditions
- Fuel load reduced, thus reducing risk of wild firesWeed control improved, reducing amount of chemicals placed in the environment
- Reduction of weeds results in less water used, improved run-off and encourages indigenous plants, especially grass, to return
- Fire accelerates breakdown of matter, reduces risk of build-up on the forest fioor and makes nutrients more readily available to the trees, thus optimising yieldIt is now possible to burn natural areas adjacent to pre-burned compartments.
- No need to make tracers on boundaries thus saving costs and potential damage eg erosion.
- Improved access to compartmentsOpportunities for agro-forestry.
Published in March/April 2008