The Aliens are Taking Over!!!

This conjures up ideas of little green men from outer space running around taking over the earth!! Although this is not strictly what we are talking about here, they are green and they are taking over many indigenous tracts of land and our ricers and dams. We are of course referring to alien plants!! Alien plants in South Africa are those plants that do not originate in our country. They have been introduced over the years by people travelling here, either on purpose, because they were attractive, or by accident through importing of food etc. Some of these plants can be called invaders as they are capable of spreading into the indigenous vegetation and taking over or displacing it, for example the Black Wattle which originated in Australia. Other alien invaders to note are:- Lantana, Bramble, Willows, Port Jacson Willows, Water Hyacinth, Azolla etc. (the latter two being water plant invaders). At present South Africa's flora is under threat from foreign invaders and in order to preserve our wonderful floral diversity we must become aware of the problem and take action.

Invaders have some of the following characteristics in common:

  • They grow very fast and therefore gain the upperhand with regard to competition for water, light, space and nutrients.
  • They are adaptable and thrive in a wide range of ecological environments, biological controls (insects, disease etc) are absent.
  • They are very hardy and can withstand unfavourable conditions - they produce numerous seeds which propogate easily eg. Black wattle can withstand drought and fire and the seed can remain viable for many years, Prickly Pears and Willows reproduce vegetatively.

    Invaders are found among all plant types such as trees, climbers and shrubs as well as grasses and water plants. All of them have a marked effect on the ecological balances in the environment they inhabit. This in turn has an impact on the animal life. Human endeavour in the form of development or overgrazing can add to the problem. It is therefore important that we begin to find ways of eradicating these pests, thus returning the local environment to the rightful floral inhabitants.

    (Courtesy of Deltalk, Summer Edition Vol 13 1997)

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