Conservation scientists are increasingly warning about the spread of invasive alien species (IAS) — non-native organisms that are rapidly transforming India’s ecosystems. These “stealth invaders” are eroding native biodiversity, altering habitats, and triggering human–wildlife conflicts. The challenge now is whether to first document their impacts fully or to design conservation responses simultaneously.
What Are Invasive Alien Species?
Invasive alien species are plants, animals, or microorganisms that are introduced outside their natural range—intentionally or accidentally—and then establish, spread, and cause harm to the environment, economy, or human health.
They may be introduced as ornamental plants, exotic pets, for aquaculture, soil improvement, or pest control. Once established, they often outcompete native species, reduce biodiversity, and change ecosystem functions.
Key Facts for Prelims
| Aspect | Details |
|---|---|
| Definition (CBD) | Species whose introduction and/or spread outside their natural past or present distribution threatens ecosystems, habitats, or species. |
| Global Estimate | ~37,000 established alien species worldwide; ~3,500 (≈10%) cause significant harm. (K.V. Sankaran, former Director, KFRI) |
| India’s Estimate | ~139 documented invasive alien species; many others remain poorly studied. |
| Introduction Pathways | Ornamental trade, aquarium and aquaculture industries, forestry, pest control, accidental transport, and biological introductions. |
| Notable Terrestrial Invasives (India) | Lantana camara, Parthenium hysterophorus, Prosopis juliflora, Chromolaena odorata. |
| Notable Aquatic Invasives | Water hyacinth (Pontederia crassipes), Alligator weed (Alternanthera philoxeroides), Duck weed (Lemnoideae spp.), Water lettuce (Pistia stratiotes). |
| Notable Invasive Animals | Yellow crazy ant (Anoplolepis gracilipes), African catfish (Clarias gariepinus), Tilapia, Apple snail. |
| Example – Lantana camara | Introduced by the British as an ornamental shrub; now blocks elephant movement corridors, increases human–wildlife conflict. |
| Example – Prosopis juliflora (“Gando Bawar”) | Introduced to the Banni grasslands (Kutch) for soil reclamation; now occupies >50% of the area, depletes groundwater, and degrades native grasslands. |
| Example – Water Hyacinth | Among the world’s 10 worst invasives; blocks waterways, depletes oxygen, hampers fisheries, and promotes mosquito breeding. |
| Alien Aquatic Fauna in India | ~626 alien aquatic species (R. Raghavan, KUFOS) — mainly from aquarium trade, aquaculture, mosquito control, and sport fishing. |
| Impact | Alters soil composition, water chemistry, nutrient cycling, and light availability; disrupts food webs; reduces genetic diversity; causes local extinctions. |
| Legal/Policy Frameworks | – Biological Diversity Act, 2002 – National Biodiversity Authority (NBA) regulations – Forest Policy (1988) and National Biodiversity Action Plan (2008) – IPBES Invasive Alien Species Assessment (2023). |
| Global Convention | Convention on Biological Diversity (CBD) – Article 8(h) calls for prevention, control, or eradication of IAS. |
Ecological and Socio-Economic Impacts
- Biodiversity loss: IAS outcompete native flora and fauna, leading to species decline or extinction.
- Habitat alteration: Modify soil porosity, nutrient cycles, and water flow; reduce forest regeneration.
- Agricultural loss: Crop damage by insect pests and weed competition; indirect yield losses.
- Water crisis: Species like Prosopis and Eucalyptus deplete groundwater; aquatic weeds block irrigation channels.
- Human–wildlife conflict: Species such as Lantana displace herbivores into croplands.
- Economic burden: Management costs, reduced fishery productivity, and loss of ecosystem services.
India’s Policy and Research Gaps
- Limited baseline data and documentation of invasive spread.
- Weak coordination between environment, agriculture, and fisheries departments.
- Inadequate quarantine controls for ornamental and aquarium species.
- Few impact assessments linking IAS with socio-economic outcomes.
- Lack of unified eradication or restoration frameworks.
Experts argue that documentation and conservation should proceed in parallel, as waiting for exhaustive data could delay urgent mitigation. Standardised impact-mapping methods and community-based monitoring (citizen science) can help identify priority areas for control.
Reference: The Hindu
