Invasive alien species (IAS) are plants, animals, pathogens and other organisms that are non-native to an ecosystem, and which may cause economic or environmental harm or adversely affect human health. They are major global change drivers. In particular, they impact adversely upon biodiversity, including decline or elimination of native species through competition, predation or transmission of pathogens and the disruption of the local ecosystem and ecosystem function.
Under regular conditions, communities are made up of a variety of species that developed in the areas and co-exist in harmony and balance. When a non-native species is introduced, it can grow in an uninhibited manner without the natural controls of its original area. Non-native species can be aggressive or vigorous growers and can overwhelm and outcompete the local native species. This upsets the natural balance and results in the loss of the native species and sometimes whole communities, thereby lowering the overall biodiversity and health of an area.
Insects can get into the wood, shipping palettes, and crates that are shipped around the world.
Invasive species may arrive in new areas through natural migration, but they are often introduced by the activities of other species. Human activities, such as those involved in global commerce and the pet trade, are considered to be the most common ways invasive plants, animals, microbes, and other organisms are transported to new habitats. Such species are primarily spread by human activities, often unintentionally. People, and the goods we use, travel around the world very quickly, and they often carry uninvited species with them. Ships can carry aquatic organisms in their ballast water. Insects can get into the wood, shipping palettes, and crates that are shipped around the world. Some ornamental plants can escape into the wild and become invasive. And some invasive species are intentionally or accidentally released pets.
Invasive species are among the leading threats to native wildlife. Approximately, 42% of threatened or endangered species are at the risk due to invasive species. Invasive species cause harm to wildlife in many ways. When a new and aggressive species is introduced into an ecosystem, it may not have any natural predators or control. It can breed and spread quickly, taking over an area. Native wildlife may not have evolved defences against the invader or they may not be able to compete with a species that has no predators.
The invasive species may provide little to no food value for wildlife. Invasive species can also alter the abundance or diversity of species that are important habitats for native wildlife.
The direct threats of invasive species include preying on native species, outcompeting native species, for food or other resources, causing or carrying disease and preventing native species from reproducing or killing a native species’ young. They can change the food web in an ecosystem by destroying or replacing native food sources. The invasive species may provide little to no food value for wildlife. Invasive species can also alter the abundance or diversity of species that are important habitats for native wildlife.
Additionally, some invasive species can affect us by degrading soil, leading to erosion that can lower the quality of water. They crowd out and can kill important native trees and plants that provide shade, carbon storage and habitat for native wildlife. And they can even increase the risk of wildfire. When these non-native plants and animals establish themselves in our local ecosystems, they outcompete and dislodge species that have evolved specifically to live there.
Hence, early detection and timely management of invasive species are a burning issue of the present condition. The best way to fight invasive species is to prevent them from occurring in the first place, which is followed by controlling and eradication of IAS from the non-native environments.
(M.Sc 4th semester Central Department of Zoology TU, Kirtipur, Kathmandu)
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