In this case ‘beneficial’ alien species can include ornamental plants, but mostly refer to plants that are used for food, fibre and medicinal compound production.
A wide range of detrimental effects are associated with invasive plants and include:
• Negative effects on biodiversity.
• Growth of surrounding or affected plants.
• Water quality impacts.
• In some cases, soil health.
Many invasive species have no negative effect on soil health but certain species, such as those discussed below, have very distinct impacts.
What is soil health?
Soil health is broadly defined as the sustained potential of a soil to function as a growth medium for plants and soil organisms, through the provision of nutrients, water and habitat, for the longterm health and benefit of man and the environment.
This concept is very broad and has to be applied with caution. The natural soils of South Africa vary significantly along climatic (rainfall) gradients, geological zones, topography, organisms (all living organisms – big and small) and landscape age. The specific conditions have, under natural conditions, led to the very distinct natural heritage of South Africa that is characterised by a wide range of plants, animals and soils.
These soils therefore have very specific combinations of characteristics that make up the localised ‘soil health’ features. It is within these specific areas that invasive plant species can detrimentally impact on plant or animal species.
The effect of agriculture
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