Question

Invasive alien plants are estimated to cover 10 million hectares (ha) in South Africa. Every year they use approximately 3,3 billion cubic metres (m3) of water more than the amount of water used by indigenous plants.

1 Differentiate between alien plants and indigenous plants.
2 Describe the impact on water quality if alien plants cover such a
large area of South Africa.

3 Define and differentiate between biological control and chemical
control of invasive alien plants.

Answer 1

1 Alien plants are plants that do not naturally live or originate in a particular habitat or country. Indigenous plants are plants that are naturally found in a particular habitat.

2  Results in blocked waterways. Light is not able to enter.
  Photosynthesis cannot occur and plants die and decompose.
  Bacteria deplete oxygen supply in water which results in death of aquatic animals.
3 Biological control is controlling alien plants through use of natural pests.
  It is a more environmentally friendly and safe way of controlling alien plants.
  Chemical control is the use of chemicals to prevent the spread of alien plants.
  It can kill desirable plant and animal species, instead of only targeting the intended species.