Impacts and Control of Invasive Alien Plants in South Africa #ConservationTuesday
Invasive alien species are plants of exotic origin, which are invading areas that were previously ecological niches containing only indigenous vegetation .
Invasive alien plants are a significant problem in South Africa as they have negative impacts on the environment by decreasing both surface water runoff and groundwater recharge, causing direct habitat destruction, intensify flooding, and increasing the risk and intensity of wildfires (Görgens and Van Wilgen, 2004).
With invasive plants having high evaporation rates, they often use more water than surrounding indigenous plants, which has a direct impact on stream flows and groundwater reserves. In South Africa, an estimate of 1.44 billion m3 of water is lost to invasive plants annually. To put it in perspective, this amount of water loss is enough to provide 3.38 million households with four inhabitants with water for a year or to irrigate 120 000 hectares of cropland (WWF, 2016).
According to the Biodiversity Act 10 of 2004, it is stated that landowners are under legal obligation to control invasive alien plants occurring on their properties. Landowners must then identify all invasive alien plants on their property and make use of the correct methods to control or remove these plants.
The control methods of alien invasive plants can be broadly classified into three categories: mechanical, chemical or biological. Mechanical control methods involve the physical destruction or total removal of plants (e.g. felling, strip-barking; ring-barking, hand-pulling and mowing); chemical control of invasive alien plants include the foliar spraying of herbicides to kill targeted plants and biological control or biocontrol methods involves the release of natural enemies that will reduce plant health and reduce population vigour to a level comparable to that of the natural vegetation.
It is often necessary to use a combination of at least two of these methods to control or remove invasive alien plants (State of the World Plants, 2017). With repeated follow-up, mechanical and chemical control methods tend to be short-term activities suitable for smaller plant invasions that can result in the complete removal of the target species. After the implementation of your methods, it is important to evaluate the effectiveness of your methods and to monitor the cleared areas on a regular basis to identify emergent seedlings and to remove those immediately.
Some of the main RSA invaders:
Rooikrans, Australian Blackwood, Honey-thorn, Silver Wattle, Pepper-tree, Lantana, Queen of the night, Prickly Pear.
Overall, the management of invasive alien plants in South Africa is of utmost importance as it can increase runoff, improve water quality, minimize fire risk and prevent the extinction of our indigenous vegetation.
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