Q.Alien species invasion has been a threat to biodiversity. Justify with the help of a suitable example. List any other three causes responsible for such a loss.
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Start your 14-day free trial to unlock the full solution →Alien species, when introduced into new ecosystems, can outcompete or prey upon native species, leading to their decline or extinction, and this is one of the four major causes of biodiversity loss.
Biodiversity, the rich variety of life on Earth, is facing unprecedented threats, leading to a rapid decline in species populations and even extinctions. Among the most significant dangers is the introduction of alien species into ecosystems where they do not naturally belong. These introductions, often unintentional but sometimes deliberate, can have devastating consequences for native flora and fauna.
An alien, or exotic, species is one that has been introduced to an area outside its native range. When such a species enters a new ecosystem, it often finds itself free from the natural predators, parasites, and diseases that kept its population in check in its original habitat. This lack of natural controls allows the alien species to proliferate rapidly, often outcompeting native species for resources like food, light, and space. In some cases, the alien species may directly prey on native species, introduce new diseases, or alter the habitat in ways that make it unsuitable for the indigenous inhabitants. The native species, having evolved in isolation from these new competitors or predators, are often ill-equipped to cope with the sudden pressure, leading to their decline and, in severe cases, extinction.
A stark example of the destructive potential of alien species invasion comes from Lake Victoria in East Africa. The introduction of the Nile Perch, a large predatory fish, into the lake in the 1980s had catastrophic effects. The Nile Perch rapidly consumed the native cichlid fish species, which were endemic to Lake Victoria and known for their incredible diversity. Within a short period, over 200 species of cichlid fish became extinct, representing one of the most dramatic examples of species extinction due to an alien invasion. This single act of introduction not only decimated the lake's unique biodiversity but also had profound ecological and socio-economic impacts on the region. Other notable examples in India include the invasive weeds Parthenium (carrot grass), Lantana, and Eichhornia (water hyacinth), which have caused environmental damage and threatened native species. Similarly, the illegal introduction of the African catfish (Clarias gariepinus) for aquaculture purposes poses a threat to the indigenous catfish in Indian rivers.
The introduction of the Nile Perch into Lake Victoria led to the extinction of over 200 species of native cichlid fish, serving as a classic example of biodiversity loss due to alien species invasion.
While alien species invasion is a critical threat, it is one of several major causes contributing to the ongoing biodiversity crisis. Ecologists often refer to the four major causes as the "Evil Quartet." Besides alien species invasions, the other three significant causes responsible for biodiversity loss are: …
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