Why in News ?
- Conservation scientists warn about “stealth invader” species—invasive alien species (IAS)—that are rapidly transforming Indian landscapes and eroding local biodiversity.
- India faces a research-policy dilemma: whether to first document all IAS impacts or simultaneously conserve and study.
- The issue has gained urgency amid rising economic and ecological losses globally from IAS.
Relevance:
- GS-3 (Environment & Biodiversity): Biodiversity conservation, invasive alien species (IAS), ecosystem services, SDG 14 & 15.
- GS-2 (Governance/Policy): National Biodiversity Action Plan, IAS management, biosecurity policies.
What Are Invasive Alien Species (IAS)
- Definition: Non-native species introduced intentionally or accidentally into new ecosystems.
- Pathways of introduction:
- Accidental: through trade, transport, or ballast water.
- Intentional: for ornamental purposes, pest control, or land restoration.
- Once introduced, these species:
- Outcompete native flora and fauna,
- Alter habitats and food webs,
- Reduce agricultural productivity,
- Cause local or global extinctions.
Global Scenario
- 37,000 established alien species introduced worldwide due to human activity.
- ~200 new alien species added every year.
- 10% (~3,500 species) have documented harmful impacts on ecosystems and people (K.V. Sankaran, former Director, Kerala Forest Research Institute).
- Economic and non-economic losses: biodiversity degradation, soil decline, crop yield loss, and altered hydrology.
Status in India
- 139 identified invasive alien species, mostly insect pests of crops (Ankila Hiremath, ATREE).
- Others indirectly affect crops by disrupting native pest-control insects.
- IAS threaten ecosystems ranging from forests to freshwater bodies.
- India’s invasion biology research remains fragmented and poorly documented.
Case Studies: Key Invasive Species in India
A. Lantana camara
- Introduced as ornamental shrub during British rule.
- Now widespread, blocking conservation of elephants and other large herbivores.
- Thrives in diverse soil types, unpalatable to herbivores, forms dense thickets.
- Ecological consequences:
- Restricts movement of elephants → human-wildlife conflict increases.
- Alters habitat structure, impeding regeneration of native plants.
B. Prosopis juliflora (“Gando Bawar”)
- Introduced from South America/Caribbean in 19th century; later spread in Gujarat’s Banni grasslands (1960s–70s).
- Originally meant to reduce soil salinity and boost green cover.
- Now covers 50–60% of grassland, causing:
- Severe groundwater depletion (“thirsty” tree).
- Competition with native Acacia and grasses.
- Soil salinisation and ecosystem imbalance, harming pastoralist livelihoods.
C. Water Hyacinth (Pontederia crassipes)
- Among world’s 10 worst invasive species.
- Dominates paddy fields, lakes, wetlands, including Kaziranga National Park.
- Impacts:
- Blocks sunlight → reduces oxygen in water.
- Harms migratory bird habitats and aquatic biodiversity.
- Increases vector-borne diseases by providing mosquito breeding grounds.
D. Other Aquatic Invaders
- Alligator weed, duckweed, water lettuce — degrade freshwater ecosystems.
- Alien fish (626 species) introduced via aquarium trade, aquaculture, mosquito control, sport fishing (Rajeev Raghavan, Kerala University of Fisheries).
- Now found in Dal Lake (Kashmir), Manipur, Telangana, Kerala, etc.
- Major threat to 1,070 freshwater fish species in India.
Ecological Impacts of IAS
| Level | Impact Type | Examples |
| Species Level | Reduced survival, reproduction, and genetic diversity | Native fishes and ants displaced |
| Population Level | Decline in population size, reduced range | Native ant populations replaced by yellow crazy ant |
| Community Level | Disruption of food webs, altered predator-prey balance | Herbivore-plant interactions altered by Lantana |
| Ecosystem Level | Changes in soil porosity, water turbidity, nutrient cycles | Prosopis altering Banni hydrology, hyacinth affecting lakes |
Key Scientists’ Perspectives
- Ankila Hiremath (ATREE):
- IAS like Lantana and Prosopis modify soil and water balance, worsening wildlife conflicts.
- Achyut Banerjee (Azim Premji University):
- IAS degrade natural habitats, disrupt predator-prey dynamics.
- Rajeev Raghavan:
- Alien fishes threaten India’s endemic freshwater fauna; freshwater invasion biology is “still in its infancy”.
- Alok Bang (Azim Premji University):
- Emphasizes defining “conservation” scientifically, given differing stakeholder perceptions.
- Advocates for simultaneous documentation and conservation instead of waiting for exhaustive records.
Documentation and Research Gaps
- Most IAS in India lack invasion histories, spread maps, and ecological assessments.
- Absence of standardised methods for:
- Impact measurement,
- Cumulative effect mapping,
- Cross-species ecological modeling.
- Freshwater invasion biology particularly underdeveloped.
- Need for micro-level data on distribution, native–alien interactions, and ecosystem-level impacts.
Policy Dilemma: Document or Conserve?
- Option 1: Wait for full documentation → impractical, resource-heavy, time-consuming.
- Option 2 (preferred): Parallel approach — conduct conservation planning and impact studies simultaneously, learning from global experiences.
- India should:
- Use foreign ecological case studies to anticipate local outcomes.
- Prioritize high-impact species and regions for early intervention.
Recommended Strategies
- Develop standardized quantitative methods to assess IAS impacts (species & ecosystem scale).
- Create IAS atlases through citizen science and digital mapping tools.
- Identify invasion hotspots and prioritize management pathways.
- Encourage multi-stakeholder collaboration among scientists, forest departments, farmers, and local communities.
- Integrate IAS management into:
- National Biodiversity Action Plan,
- National Mission on Biodiversity and Human Wellbeing,
- State Wildlife Action Plans (2023–2033).
- Promote biosecurity measures for imports, aquaculture, and ornamental trades.
Broader Implications
- IAS threaten India’s biodiversity hotspots — Western Ghats, Northeast India, and Andaman–Nicobar.
- Undermines ecosystem services like pollination, carbon sequestration, and soil fertility.
- Causes economic losses in agriculture, forestry, and fisheries.
- Aggravates human-wildlife conflict and pastoral distress.
- Affects SDG 14 (Life Below Water) and SDG 15 (Life on Land) targets.
Conclusion
- Invasive alien species are a silent but escalating threat to India’s ecological stability.
- Their multi-level, cascading impacts demand immediate, integrated, and adaptive management.
- India must move beyond fragmented studies to a national IAS strategy emphasizing:
- Rapid detection,
- Risk assessment,
- Restoration of invaded ecosystems,
- Public participation and awareness.
- Without decisive action, IAS could irreversibly reshape India’s biodiversity and rural livelihoods.
