Post-fire environmental rehabilitation

Article by Herman Pieters in collaboration with Pam Booth (Knysna Municipality) and Nandi Mgwadlamba (SANParks)

The dry and warm climate trends across the globe are conducive to a variety of natural disasters. Dry weather makes green vegetation bone-dry and flammable.  Wildfires cause a range of imbalances, leading to adverse environmental and socioeconomic results. While the cause of the fire is still under investigation, factors that fuelled the fire include a dry and warm climate which has become a trend globally.

Factors influencing high-risk classification of a post-fire environment

The physical transformation that soil undergoes during fires change many factors, but most obvious is the impact on organic matter litter and mineral soil layers below the surface. Organic matter moves downward, below the visible eye, and forms a water-repellent layer that increases surface runoff and results in erosion during the first rains following a fire.

Fire-induced soil changes have the potential to increase flooding and erosion, which have downstream effects on water quality and the aquatic habitat.

High-risk hotspots have been identified

When assessing the fire and storm affecting Garden Route, Geographical Information System (GIS) mapping plays a vital role in identifying high-risk areas in need of immediate rehabilitation. GIS technology is used to capture, analyse and present digital geographic data. Environmental specialists not only rely on GIS technology to identify high-risk areas but also do site visit (ground-truthing) to confirm GIS findings. High-risk areas are those posing a threat to safety and to downstream catchments and ravines and man-made infrastructure. These areas are prioritised because of the immediate danger of erosion and mudslides.

High-risk areas include:

  • Brenton-on-Sea
  • Brenton-on-Lake
  • Belvidere
  • Phantom Pass
  • Knysna Heights

Some landowners, notably those in Belvidere Heights, have installed effective silt fences and brush lines.

The following interventions are underway:

  • Installing bio-sausages to slow water velocity, which will reduce sediment flow along steep slopes.
  • Felling and scaling down of dead brush and trees.
  • Stacking of biomass along contour lines.
    Stacked lines provide a micro habitat, allowing for faster plant regeneration.
  • Monitoring of plant regeneration for invasive alien plant regrowth
  • Herbicide application to expected alien invasive plant areas.
  • Seeding of slopes above bio-sausages to fast-track the regrowth of ground cover.
  • Hydromulching – fast, economical and efficient grass planting.

The following are trees and dune plant species effective for post-fire rehabilitation:

Trees

  • Podocarpus falcatus
  • Ekebergia capensis (Essenhout)
  • Virgilia divaricata (Keurboom) – nitrogen fixing
  • Buddleia saligna
  • Buddleia salviifolia
  • Burchellia bubalina (Wild Pomegranate)
  • Celtis africana (White Stinkwood)
  • Halleria lucida (White Olive)
  • Kiggelaria africana (Wild Peach)
  • Nuxia floribunda (Forest Elder)
  • Rapanea melanophloeos – Boekenhout
  • Tarchonanthus littoralis – Camphor
  • Psoralea pinnata

Dune specific

  • Diospyros dichrophylla (Monkey Plum)
  • Asparagus rubicundus and other Asparagus species
  • Zygophyllum morgsana (and other species (Zygophyllum is a synonym of Roepera))
  • Carissa bispinosa
  • Pterocelastrus tricuspidatus (Candlewood)
  • Colpoon compressum
  • Maytenus procumbens
  • Ehrharta ramosa (grass)
  • Carpobrotus edulis (yellow flower) or C. Deliciosus (pink flower)
  • Erica discolor subsp speciosa
  • Salvia africana-lutea
  • Leucadendron salignum
  • Leucospermum glabrum
  • Rhus chirindensis (Rhus is a synonym of Searsia)
  • Rhus lucida
  • Rhus crenata (dune-Crow- Berry)

Restoration efforts will enhance post-fire recovery and will cater for both short- and long-term rehabilitation.