What are invasive species?

• An invasive species can be any kind of living organism—an amphibian, plant, insect, fish, fungus, or bacteria—that is not native to an ecosystem and causes harm. 
• The Convention on Biological Diversity (CBD) defines invasive species as “an alien species whose introduction and spread threaten ecosystems, habitats, or species with socio-cultural, economic and environmental harm and harm to human health”.
• Not all non-native species are invasive. For example, most of the food crops grown in India, including onion, potato and tomatoes are not native to the region.
• To be invasive,
  • a species must adapt to the new area easily
  • it must reproduce quickly 
  • it must harm the economy, or the native plants and animals of the region.
• Some of the most serious invasive species in India are Alternanthera philoxeroides, Cassia uniflora, Chromolaena odorata, Eichhornia crassipes, Lantana camara, Parthenium hysterophorus and Prosopis juliflora, Senna Sepctabilis, etc.

Invasive Alien Species – a cause of concern

• Forest-invasive species can supplant native plants, eliminate food and cover for wildlife and threaten rare plant and animal species.
• The impact of globalisation leading to the increased movement of people, trade and deforestation have led to the introduction of invasive species in the indigenous environment in massive quantities.
• The spread of invasive species is alarming and is wiping out local native species like grasses and other herbaceous species. As a result, the local food chain is affected with the invasive species competing for space and light with native flora.
• Eg: The widespread prevalence of invasive species like Lantana camara has reduced the proportion of natural grasses for herbivorous animals forcing their movement to human habitats in search of paddy crops and other edible items.
• These species can change the functions of ecosystems and increase losses in forestry and natural resource management costs as well as being a potential threat to livestock health.
• The unchecked growth of invasive species affects soil health, which is prone to faster deterioration.

Why in News?

• The Madras High Court has called for monthly progress reports from District Collectors across Tamil Nadu on the eradication of the exotic and invasive species of shrub Prosopis juliflora that is considered harmful to the ecology.
• It also issued directions to the District Collectors with respect to eradication of the shrub from forests and water bodies across the state.

reference:

https://www.nwf.org/Educational-Resources/Wildlife-Guide/Threats-to-Wildlife/Invasive-Species