Invasive alien species include organisms, animals and plants which are foreign to a region or ecosystem. Invasive alien species may have a negative effect on human health and on the environment, which may lead to a negative effect on the economy. Furthermore, they have an adverse impact on biodiversity which has led to the decline of indigenous species, due to the disturbance of ecosystems through predation and competition. Costs of this problem occur on an ecological, social and economic level. The occurrence of invasive alien species threatens development due to the fact they have a negative impact on fisheries, forestry, agriculture and natural systems which people rely on for their livelihoods especially in developing countries. The significant increase of invasive species globally has resulted in the homogenizing of the world’s fauna and flora. Invasive alien species are recognized as one of the primary causes of biodiversity loss globally. South Africa has declared 379 alien plant species, which includes weeds and invaders. Invasive alien plants spread rapidly and have the ability to displace the indigenous plants. Negative impacts of invasive alien plants include biodiversity loss, high water use, and the increased intensity and frequency of fires.
Legislation has been incorporated to combat the problem of invasive plant species which threaten the natural flora and the valuable water resources. The Department of Environmental Affairs (DEA) manages invasive alien species under the National Environmental Management: Biodiversity (NEM:BA) Act 10 of 2004. Notice 3 of NEM:BA lists 379 plant species that are legally declared invasive species. Each species is assigned to one of three categories based on the level of threat posed by the species and the legal status assigned to each:
• Category 1a – Plant species that must be combatted or eradicated. • Category 1b – Plant species that must be controlled. • Category 2 – Plant species that must not be allowed to spread outside any property. • Category 3 – Plant species that when occurring in riparian areas must be considered to be category 1b Listed In order to raise public awareness, the Department of Environment, Forestry and Fisheries (DEFF) has launched the National Invasive Species Week (NISW) from October 7th – 11th of October 2019. Some of the most widespread offending species are Acacia mearnsii (Black Wattle), Chromolaena odorata (Triffid weed), Melanoxylon (Blackwood), Lantana camara (Lantana), Pinus pinaster (Cluster pine) and Solanum mauritianum (Bugweed). Invasive plants are a significant problem that requires active participation from the public and private sectors to combat this increasing threat.
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