Invasive Alien Species in India — The Dilemma of Documentation vs. Conservation
Context
Conservation scientists in India are raising concerns over invasive alien species (IAS) that are threatening native biodiversity, ecosystems, and livelihoods.
The dilemma:
Should India first document the effects of all invasive species before preparing conservation plans, or conduct both documentation and conservation simultaneously?
Understanding Invasive Alien Species (IAS)
Definition: Non-native species introduced into a landscape (intentionally or accidentally) that spread aggressively, displacing local flora and fauna.
Modes of Introduction:
As ornamental fish or decorative shrubs.
For revegetation of degraded land or soil stabilisation.
Through aquaculture, aquarium trade, and transportation.
Impacts:
Displace native biodiversity.
Alter soil, water, and light conditions.
Change predator-prey relations.
Cause local or global extinctions.
Lead to habitat destruction and human-animal conflicts.
Global and Indian Scenario
Component | Global Data | Indian Context |
Total established alien species | ~37,000 | ~626 alien aquatic species; 139 invasive alien species recorded |
New introductions annually | +200 each year | Mostly insect pests, ornamental plants, aquatic weeds |
% with harmful impacts | ~10% (≈3,500 species) | Affect biodiversity, soil, water, and agriculture |
Key Invasive Species and Impacts
A. Terrestrial Invasives
Species | Origin / Introduction | Impacts |
Lantana camara | Introduced by British as a colourful shrub | Unpalatable to herbivores; blocks elephant movement; forces animals to crop areas → human-wildlife conflict |
Prosopis juliflora (“Gando Bawar” / Mad Tree) | Brought from South America & Caribbean (19th century); expanded in 1960s–70s by Gujarat Forest Dept. for soil reclamation | Covers 50–60% of Banni grassland; depletes groundwater; increases salt-water intrusion; disrupts pastoral networks |
Parthenium hysterophorus | Accidental introduction | Aggressive weed; reduces crop yield; allergenic pollen |
B. Aquatic Invasives
Species | Type / Origin | Impacts |
Water hyacinth (Pontederia crassipes) | South America | Chokes lakes and paddy fields; reduces oxygen; affects migratory birds; among world’s 10 worst invasives |
Alligator weed (Alternanthera philoxeroides) | South America | Degrades aquatic habitats |
Duckweed (Lemnoideae spp.) | Aquatic plant | Rapid spread; affects light penetration |
Water lettuce (Pistia stratiotes) | Aquatic weed | Blocks sunlight, disrupts aquatic ecosystems |
Yellow crazy ant (Anoplolepis gracilipes) | Invasive insect | Reduces native ants that control crop pests |
Ecological Consequences
A. At the Species Level
Reduces native species’ ability to survive and reproduce.
Leads to local extinctions or range contractions.
B. At the Population Level
Shrinks population size and genetic diversity.
C. At the Community Level
Alters species composition and ecosystem functioning.
D. At the Ecosystem Level
Changes food webs, nutrient cycling, energy flow, and primary productivity.
May transform entire ecosystems into novel ecological systems.
Challenges
Poor documentation: Lack of recorded invasion histories, spread maps, or quantified impacts.
Freshwater invasion biology is still in its infancy in India.
Insufficient data on interactions between alien and native species.
Ambiguity in “conservation” goals across stakeholders.
Limited interdisciplinary collaboration among ecologists, policymakers, and communities.