Invasive Alien Species: Characteristics, Examples and Impacts

Context: Apart from mechanical and chemical control methods to tackle invasive plant species, scientists also employ classical biocontrol agents such as fungi.

About Invasive Alien Species

• According to the Convention on Biological Diversity (CBD), invasive species are introduced outside their natural distribution and threaten biodiversity.
  • Characteristics: Ability to arrive, survive, and thrive in new environments by reproducing quickly and outcompeting native species for resources.
• In India, Under the amended Wildlife Protection Act, 1972 (2022), they are defined as non-native species whose introduction or spread could negatively impact native wildlife or habitats in India.
  • However, this definition does not cover invasive species only in certain regions within India, such as the chital in the Andaman.

Examples of Invasive Species in India

Fauna

• Fish: African catfish, Nile tilapia, red-bellied piranha, and alligator gar.
• Turtles: Red-eared slider, which is a common exotic pet that competes with local species for food and habitat.
• Chital: Introduced by the British in the early 20th century, they have no natural predators on the islands and have become an invasive species, spreading across the Andaman archipelago.

Flora

• Mikania micrantha (also called “mile-a-minute weed“) — native to Central and South America but introduced multiple times to India — is now a major invasive plant affecting biodiversity and crops.

Impacts of Invasive Species

• Ecological Damage: Displace or eliminate native flora and fauna
  • Threaten endangered species (Eg., Manas Wildlife Sanctuary’s grasslands impacted by Mikania)
• Economic Losses: Lower agricultural and plantation yields (Eg., tea, teak, rubber)
  • Costly to manage and control.
• Biodiversity Threats: Lead to the extinction of endemic species
  • Disrupt ecological balance (g., Indian mongoose introduced to control rats ended up harming local wildlife)
• Public Health Concerns: Some invasive plants cause allergies and skin irritation (Eg., Parthenium).

Control Measures for Invasive Alien Species

Mechanical Control

Manual weeding, uprooting, and burning

• Effective but labour-intensive and temporary
• Mikania grows several cm/day — difficult to match by manual removal.

Chemical Control

Use of herbicides and pesticides

• Often environmentally harmful and costly
• Effects may not be long-lasting

Classical Biological Control

Introduction of natural enemies (insects, fungi, pathogens) from native habitats

• Example: Puccinia spegazzinii fungus used against Mikania micrantha
  • Zygogramma bicolorata beetle used against Parthenium hysterophorus
  • Weevil Cyrtobagous salviniae for Salvinia molesta
• Policy and Regulatory Measures: Strengthening quarantine laws and biosecurity
  • Timely approval of biocontrol agents
  • Raising awareness among farmers and stakeholders
• Research and Monitoring: Continuous ecological research to identify suitable biocontrol agents
  • Climate suitability studies, as climate change may affect efficacy.

Conclusion

Invasive species like Mikania micrantha pose serious ecological and economic threats. While chemical and mechanical methods have limitations, biological control, though slow, is a sustainable and ecologically benign strategy. However, success depends on government support, public awareness, and timely approvals.

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