Several mainly Australian plant species were introduced to the Western Cape in the first half of last century to help stabilise dunes in coastal areas and to provide a source of wood fuel. Unfortunately, these species have spread prolifically and now pose a serious threat to the local indigenous fynbos vegetation.
The principal alien invasives are wattles, eucalypts and hakeas from Australia and pines from the Mediterranean Basin and California. These areas all have a climate very similar to parts of the Cape Floristic Region.
Aliens, which are larger and more tree-like than the indigenous fynbos, are reducing fresh water runoff from mountain catchment areas by up to 50%. Dense stands of the alien trees also pose a fire hazard. Voluntary hack groups are working on the mountains above Hermanus to help fight back the invaders.
- Acacia cyclops ‘Rooikrans’ forms dense thickets on the alkaline coastal sands as well as on sandy patches in the limestone landscape.
- Acacia saligna ‘Port Jackson Willow’ and Vachellia longifolia ‘Long-leaved Wattle’ are the main invaders of acid sands.
- Acacia mearnsii ‘Black Wattle’ is a rampant invader of stream-side habitats where it alters the hydrology and ecology of river systems.
- In the past decade Leptospermum laevigatum ‘Myrtle’ has spread rapidly over large areas of the Southern Overberg and has become a major invasive threat. Biological control agents have recently been introduced to counter its advance.
Hermanus Hacking Group
This active group has been funded by the Hermanus Botanical Society, the Table Mountain Fund, Overstrand Municipality and individual sponsors. At present close to R2000 per week is being spent on labour. The areas tackled by HHG have been Northcliff, Elephant Path and adjacent mountainside, Hoy's Koppie and more recently the start of Rotary Way, the mountainside area opposite Gateway Centre and the eastern side of Bosko Church and adjoining mountain.
It is targeting, in particular, the invasive daisy Senecio pterophorus 'Perdegifbos', the invasive weed Dittrichia graveolens 'Stinkwort' and Hakea gibbosa.
Section leaders of the Cliff Path Management Group (CPMG) together with available Coast Care workers continue to battle kikuyu and garden escapees.
Mossel River rehabilitation project
One of the most successful hack stories started in 1998 with a dedicated group of hackers under the auspices of the Hermanus Botanical Society single-mindedly setting out to eradicate aliens clogging the Mossel River area. Residents in the area joined with hardcore hackers, municipality staff and alien vegetation control teams. Funds were raised to employ workers for heavy cutting and backup work. Gradually the river began to run free once more: the Blue Fonteinbos, pink Pelargoniums and gold Aspalathus blossomed in profusion as the mass of Wattle, Sesbania, Gum and Port Jackson were killed off.
On request, HHG will give quotes on the removal of alien vegetation on private property.
David Beattie - CPMG - 028 312 1358