Invasive Alien Species

Learn how to keep alien invasives at bay

HomeInvasive Alien Species

Invasive Alien Species

Invasive alien species are a global problem, with countries having to invest heavily to avoid species from other countries impacting negatively on their local ecosystems. These species are introduced primarily by humans; sometimes accidentally, while at other times very much intentionally.

Many of the organisms introduced to areas outside their natural range are beneficial, or have little or no benefit, but there are some species that we have to be concerned about – those plant and animal species that dramatically increase their numbers in the environmental and climatic region they now share with us. With no natural enemies, invasive species have a competitive advantage over indigenous species, as they are able to reproduce rapidly to spread and invade local ecosystems. They degrade the ecosystems they invade and impact negatively on our environment, economy and even our health. Alien plant species may exacerbate flooding and increase the risk of runaway fires, reduce our natural water resources, impact on the natural functioning of ecosystems and inhibit growth of indigenous vegetation. As required by law, they must be removed.

To find out more about invasive alien species in Cape Town, read more here.

The threat of invasive alien plants to fynbos regions – poster courtesy of Invasive Species SA

Guttural toad information

Five aquatic alien plants you can help remove

Kariba Weed

Parrot’s Feather

Water Lettuce

Red Water Fern

Water Hyacinth

Tips for removal of alien plant species

  • Eradication methods for terrestrial and aquatic alien plants: hand removal, mechanical removal, approved chemical and biological control.
  • Start clearing from a point as far as possible up-stream and work in a down-stream direction.
  • Start from the highest point on the bank and move downwards.
  • Stockpile cleared plants away from the river and remove within one week to a City-controlled dumpsite.
  • Regular follow-up clearing is essential.
  • Work with your neighbours.

Alien plant species you should remove and avoid planting

Please avoid planting the following species and replace existing individuals with suitable indigenous options:

Giant or Spanish Reeds

Wild Ginger Lily species

Grey Poplars

Weeping Willows

English Oak

Black Wattle

Kikuyu grass


Castor-oil plant

Brambles / Blackberries

St. John’s Wort

Red Sesbania

Download the NCC alien clearing manual to see a list of alien species as well as various methods of removal


Become an Alien Invasive Spotter

If you spot an alien invasive species please contact the City of Cape Town on



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