Alien plants are a major threat to the success of indigenous species. Discuss FOUR possible
reasons why alien plants were imported to South Africa, FOUR unfavourable effects of alien
plants in South Africa and FOUR strategies to eradicate alien plants.
Possible reasons why alien plants were imported to South Africa.
• Used as wind breaks in farming land.
• For the manufacture of timber products and paper.
• Various plants were imported for agricultural purposes.
• Used in tannery.
• For aesthetic reasons.
• As ornamental plants.
• Support in mines in the form of grasses that absorb acids from mine dump soil.
The unfavourable effects of alien plants in South Africa.
• Alien plants out-compete the indigenous plants, causing major changes to the
habitats in which they occur and affect the functioning of entire ecosystem.
• (They become invasive) e.g. water hyacinth cover the surface of water and block
out the sunlight, thus disturbing the food webs in these habitats.
• They cause major damage to biodiversity of the region.
• They are known to use more water than the indigenous plants.
• Increase the risk of soil erosion.
• Invasion of alien plants destroys many beautiful indigenous plants and therefore,
reduces the natural beauty of South Africa.
• Decreases natural food resources and habitat of wild animals.
Strategies to eradicate alien plants
• Mechanical control: Removal of alien plants by hand or with machines. This
method is only effective in controlling small populations and also it minimises
possible harm to non-invasive alien plants.
• Chemical control: Chemical compounds can be used to prevent the spread of
alien invasive plants. This method is effective in both large and small areas. This
method has the potential of contaminating land and water resources.
Furthermore, indiscriminate use of chemicals can harm non-invasive plants as well
as other useful animals in that area.
• Biological control: It involves the release of a specific species to restrict the spread
of the invasive plants. The invasive alien plants can be deliberately infected by
pathogens to reduce their ability to reproduce.
• Stricter control of imports of alien plants by the government at every port of entry.
• Introduce heavy penalty for importing exotic plants from abroad.
• Regular monitoring and consistent follow-up on the various interventions that are
initiated by the municipalities.
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