27/05/2017 by Bridget Seroka
As we celebrate National Biodiversity day, it is easy to forget how global trading, traveling, tourism and transport have facilitated in the increased introduction and spread of alien invasive species. Biological diversity always needs to be kept in balance with the ecosystem. If this is not done, the agricultural sector, the ecosystem as well as human health could be critically and negatively impacted. Studies show that the majority of South Africans lack the basic knowledge of alien invasive species. In fact, these plants or microorganisms may be in your back yard without your knowledge. So, what are these alien invasive species? Alien invasive species are plants, animals, pathogens, and other exotic, non-indigenous or non-native species to an ecosystem, and may cause economic or environmental harm or adversely affect human health according to the National Environmental Biodiversity Act.
Globally, it is estimated that Alien invasive species are the second greatest threat to biodiversity. Alien invasive species may be introduced into an Environment intentionally or accidentally. Many invasive species are brought in by huge cargo ships that normally travel to and from South Africa and other countries transporting goods across the ocean. Some are introduced into a new area using pest control, while others descend from pets or animals that escaped or were released into the wild. But not all alien species are bad, some have no negative consequences and no documented negative impact on the environment. They might provide recreational opportunities or food sources. However, alien invasive species may exploit a resource that native species use, making the environment more favourable for them, but less favourable for native species, which allows alien invasive species to take hold in the new environment and outcompete native species for food, water, nutrient, space, and breeding site. This can cause extinction on native species and environmental harm, economic harm, or impact human health.
In agriculture, Invasive plant species can dominate crop fields and pastures, especially if they contain allelopathic possessions. This releases chemicals that suppress growth, meaning plant growth will drastically be reduced. This will upsurge cost of land preparation and maintenance, therefore increasing the price of food. This becomes a critical issue for farmers and food source. They affect the PH of soil which modify nutrient availability, resulting in erosion and land degradation. Biodiversity loss on agro-ecosystem also undermines population of the natural enemies that keep native pest under control. This causes problems for farmers who don’t have access to insecticides or other means to manage them.
Invasive plants also have negative impacts on forests and other valuable resources, with detrimental effect on the communities that rely on them. Inhabitation regeneration of native herbaceous species, including important medicine herbs and shrubs which contribute to the reduction of diversity.
Streams, lakes, reservoirs, and aquatic weeds can critically impact ecology by displacing native species. Only a few plants can grow under the canopy created. Irrigation degrade the territory and traps sediment that can be interfered by infestations which decrease water supply and promote flooding. The heavy use of chemical pesticides, insecticides, and herbicides to control invasive pests has had detrimental consequences to ecosystems across the world, leading to pollution of soil and water, as well as causing harm to plants, animals and people working in these fields. Trees and shrubs that have deep roots or a higher water requirement than indigenous species, such as pine trees, which were introduced into southern hemisphere countries for forestry purposes – have a dramatic effect on hydrology. Just a minor reduction in the availability of water can be catastrophic in areas where it is already scarce, or which are subject to persistent droughts.
Humans can be critically affected by invasive alien species which carry diseases. They could cause a variety of health problems, such as dermatitis, as well as contributing to the spread of disease. Mosquito habitat for example are floating mats of water hyacinth. Threatening 80% of growth on traditional medicinal plants that world’s rural populations depend on for their primary healthcare. Ecosystem altered by this invasive species are less able to provide important ecological services which support human activities in variety of ways.
We are already experiencing consequence of the hyacinth in Hartbeesport dam. A plant that was introduced in the nineteen seventies and now covers about sixty percent of the dam. Water hyacinth has become one of most destructive weeds because of the critical impact on biodiversity, fast reproduction rate and expensive removal method. Alien invasive species are a serious threat to biodiversity and we need act now. Prevention is always better than cure. We need to control and check our boarder gate to prevent and lower the risk of introduction of new invasive species in the country. Report alien invasive species and hand in unwanted pests to the reverent authorities.