Fiona Macleod
First they were blamed for the Cape fires, now they’re being blamed for the floods. Experts say the huge forests of alien trees planted in the catchment areas of Mpumalanga have exacerbated the flooding that ravaged the province this week.
Mpumalanga produces 39% of the country’s timber. Commercial timber, mostly pine and gum trees, covers almost 615E000ha of the province. Experts say the biggest problem with these plantations is that they speed up the run-off of water.
The huge stretches of gum and pine, neither of which are indigenous, have eradicated natural “sponges” that would absorb the water. Logging also opens up road networks as well as sterile felled areas that have no resistance to the huge volumes of water that engulfed the province this week.
“Invading alien plants are disastrous for floods,” says Guy Preston, adviser to Minister of Water Affairs and Forestry Ronnie Kasrils. “They exacerbate the flow of water. Huge trees fall down and bash the banks, changing the water courses.”
Preston says the forestry industry is generally more responsible and accountable than in the past. Bad practices like planting too close to rivers or in wetlands have been cleaned up.
The Mpumalanga Parks Board’s Kevan Zunckel points out that though forestry in riparian areas is better managed these days, 60% to 70% of the rest of the plantations still suffer the adverse effects of monoculture cultivation.
“If the grasslands that were the natural vegetation in the catchment were still there, you wouldn’t have had sedimentation of the flood waters,” he says.