Conservation scientists in India are raising concerns over the spread of invasive alien species (IAS) that threaten native biodiversity, ecosystems, and livelihoods. 

• Researchers are divided on whether to first document the full extent of invasions or act simultaneously on conservation and management.

Invasive Alien Species (IAS)

• Definition (IUCN): IAS are animals, plants or other organisms that are introduced by humans, either intentionally or accidentally, into places outside of their natural range.
• Scale of the Problem:
• • Around 1 in 10 species on the IUCN Red List are threatened by IAS.
  • Globally, about 37,000 alien species are established, of which 3,500 (10%) are harmful.
  • Nearly 200 new alien species are recorded each year.
• Impact: Displace native flora and fauna, disrupt habitats, and cause ecological and economic losses.
• Pathways: Introduced as ornamental plants, fish for aquaculture, mosquito control, or revegetation efforts.
• India’s Scenario: India has around 139 invasive alien species, most being crop pests and invasive plants that affect native biodiversity and agriculture.

Prominent Invasive Species in India

• Lantana Camara:
  • Introduced as an ornamental shrub during British rule, It  blocks elephant and herbivore habitats, forcing wildlife into crop fields and escalating human–animal conflict.
  • Thrives across varied soil types and is unpalatable to herbivores.
• Prosopis Juliflora (“Gando Bawar”):
  • Introduced in the 19th century and planted in Gujarat’s Banni grasslands to prevent soil salinisation.
  • Now covers 50–60% of the grassland, depleting groundwater and replacing native species such as Acacia.
  • Paradoxically increased salt-water intrusion and disrupted pastoral networks.
• Aquatic Weeds:
  • Water hyacinth, alligator weed, duckweed, and water lettuce dominate lakes and wetlands.
  • Water hyacinth listed among the top 10 worst invasives clogs paddy fields, bird habitats, and national parks such as Kaziranga.
  • Alien fish species introduced for aquaculture and sport fishing threaten 1,070 freshwater fish species across India. 

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Ecological and Socio-Economic Impacts

• Soil and Water Alteration: Invasive plants modify soil structure by altering porosity, nutrient composition, and water retention capacity.
• Biodiversity Loss: IAS outcompete native species for nutrients, sunlight, and habitat, leading to declines in population size, reproductive success, and even local extinctions.
  • Example: In freshwater systems, alien fish like Tilapia and Common Carp displace indigenous species such as Tor putitora(Mahseer), threatening India’s freshwater fish diversity.
• Ecosystem Transformation: Invasives alter food webs, energy flow, and nutrient cycling, often converting diverse ecosystems into monocultures.
  • Example: Invasive earthworms and snails accelerate nutrient cycling, disturbing soil microbial balance and carbon storage.
• Human–Wildlife Conflicts: When invasives degrade habitats or food sources, wildlife migrates toward human-dominated landscapes for sustenance.
  • Example: Lantana camara’s spread in forest corridors forces elephants and deer to feed on crops, increasing incidents of crop raiding and property damage.

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