Invasive alien species (AIS) are species of animals, plants, fungi or microorganisms that have entered and established in an area outside of their natural range. Species may enter a new area or region due to accidental or intentional human activities. Examples of intentional introductions include horticulture, ornamental plants, and the introduction of fish (such as rainbow trout and largemouth bass) as sport fish, while accidental introduction includes muscle species carried on the bows of ships and seeds carried on people’s clothing.
However, alien species are only considered invasive if they have a negative effect on its environment. AIS usually reproduce quickly and have few or no natural enemies and therefore they can either predate native species or outcompete native species for natural resources such as food, light, water and space, resulting in substantial impacts on their environment. or region. Climate change plays an additional role in the spread and establishment of alien species, as global warming allows the climate to be more favorable to AIS than native species, making it easier for alien species to outcompete species. native. Pollution can also promote the establishment and spread of AIS by weakening or killing native species and allowing more robust and long-lasting invasive species to establish communities in the area and outcompete native species.
The impacts associated with AIS consist of substantial changes in ecosystem properties such as species composition and thereby affecting ecosystem functioning and ecosystem services. ecosystem functioning refers to the role biota play within an ecosystem in order to maintain conditions within the ecosystem such as pH levels, nutrient levels, pollination, and food sources and species composition. Examples of this include pine trees altering the pH of soil and groundwater and thus negatively affecting the surrounding environment and the spread of invasive alien plant species in grasslands and thus making the area less productive for ranching, less productive for native grazers and altering the fire regime of the area. ISA can however be used to improve the environment in certain cases such as when the natural predator of ISA is introduced in a controlled way in order to control the population of the ISA of interest such as the spotted weevil (Macrorhoptus hispidus) used to control water hyacinth populations in South Africa.
Impacts on the ecosystem:
AIS have the ability to alter species diversity or compromise ecosystems and cause significant damage to the natural food web of an area or region by transporting diseases and pathogens to a new area, introducing a new species that outcompete native species for food sources, introducing a new type of predator to an area where native species have not yet adapted to prevent, alter soil composition, and alter the fire regimes of areas, which then further affects native species in an area. Since the health of ecosystems influences the functionality of the environment and ecosystem services as well as human health, it is imperative that the balance within ecosystems is managed and maintained as best as possible.
Impacts on human health:
The most important effect of AIS on human health is the transport and spread of diseases and viruses as well as the negative effects of AIS on agriculture and thus affecting food safety. Examples of this include the spread of the Asian Tiger Mosquito which has been linked to over 20 different diseases such as Chikugunya Fever and Yellow Fever. AIS can also bring pathogens and diseases that can devastate crops and livestock and thus negatively influence a region’s food security. AIS such as Lantana camara, a highly toxic invasive alien plant species that has become established in South Africa, has the high potential to affect livestock populations as well as affect people who do not know that the plant is poisonous and thus result in a high risk of children consuming the plant and leading to extreme illnesses and potential death.
Additionally, AIS affect humans and human health due to the change they cause in the ecology of an area and thus negatively impact ecosystem services. Ecosystem services are considered to be the benefits provided by ecosystems that can benefit humans; such as water filtration, flood suppression, pollination for agriculture and food source for livestock. This can lead to floods, droughts and food insecurity in extreme cases.
Environmental Assurance (ENVASS) has a highly trained and knowledgeable team of terrestrial fauna and flora specialists who can formulate invasive alien species management plans as well as conduct red list species assessments.