Invasive Alien Species — Threats, Management & India's Policy Response

What Are Invasive Alien Species?

An Invasive Alien Species (IAS) is a species introduced outside its natural range (intentionally or accidentally) that becomes established and spreads, causing harm to biodiversity, ecosystems, human health, or the economy.

Three conditions must be met:

1. Alien (non-native / exotic / introduced) — not naturally occurring in that ecosystem
2. Established — capable of self-sustaining populations without human assistance
3. Invasive — spreads and causes measurable harm

IAS are recognised as one of the five direct drivers of biodiversity loss, alongside habitat change, overexploitation, pollution, and climate change. The IPBES 2023 Invasive Alien Species Assessment identified over 3,500 harmful IAS globally, causing $423 billion in annual economic damages.

Pathways of Introduction

Intentional Introduction

• Horticulture / ornamental: Water hyacinth (Eichhornia crassipes) introduced as ornamental; Lantana camara as garden plant
• Forestry: Eucalyptus and Prosopis juliflora introduced for afforestation and fuel
• Agriculture / aquaculture: Common carp and Tilapia introduced for fish farming
• Biocontrol: Some introduced biocontrol agents later became invasive themselves

Accidental Introduction

• Contaminated grain imports: Parthenium hysterophorus believed to have arrived via wheat imports from the USA in 1956
• Ballast water discharge: Ships discharge ballast water loaded at foreign ports, releasing non-native marine organisms
• Cargo and packaging material: Insects and pathogens hitchhike in timber, pallets, soil
• Tourism and travel: Pathogens, small invertebrates transported on footwear, clothing

Why Are IAS Problematic? Mechanisms of Impact

Major Invasive Alien Species in India

India has recorded over 2,500 alien plant species (as of 2023), of which several have become highly invasive. The list below covers species most frequently tested in UPSC.

Invasive Plants

Invasive Animals

IAS in Indian Islands — A Critical Vulnerability

Indian islands are global biodiversity hotspots but especially vulnerable to IAS due to endemic species with no evolved defences.

Andaman & Nicobar Islands:

• Spotted deer (Axis axis) introduced in the 1950s — grazes on native forest regeneration, damages Nicobar biosphere
• Chital and feral pigs threaten nesting grounds of sea turtles and birds
• Myna birds and cats predate on native bird populations
• Invasive plants like Lantana and Mikania threaten endemic flora

Lakshadweep:

• Rats predate heavily on seabird nests and turtle eggs
• Invasive plant species alter coral island ecology
• Being low-lying coral islands, any ecological disruption has amplified impacts

The IUCN has identified island IAS as among the most serious drivers of global extinction — more than 80% of recorded bird extinctions on islands were caused by IAS.

IUCN's 100 Worst Invasive Species

The IUCN Species Survival Commission Invasive Species Specialist Group (ISSG) maintains a list of the 100 of the World's Worst Invasive Alien Species. Indian species on this list include:

• Water hyacinth (Eichhornia crassipes)
• Lantana camara
• Mimosa pigra (giant sensitive plant)
• Parthenium hysterophorus

Global Frameworks

Convention on Biological Diversity (CBD) — Article 8(h)

CBD Article 8(h) requires each Party to "prevent the introduction of, and control or eradicate those alien species which threaten ecosystems, habitats or species." This is the primary international legal obligation on IAS.

Aichi Biodiversity Target 9 (2011–2020)

Under the Nagoya CBD Strategic Plan, Aichi Target 9 aimed: "By 2020, invasive alien species and pathways are identified and prioritised, priority species are controlled or eradicated, and measures are in place to manage pathways to prevent their introduction and establishment." This target was widely regarded as one of the least-achieved Aichi Targets globally.

Kunming-Montreal Global Biodiversity Framework (2022) — Target 6

Adopted at COP15 (Kunming, 2022), GBF Target 6 requires parties to:

• Eliminate, minimise, and reduce impacts of IAS by identifying and managing introduction pathways
• Prevent introduction and establishment of priority invasive alien species
• Reduce rates of introduction of known IAS by at least 50% by 2030
• Eradicate or control IAS, especially in priority sites such as islands

Target 6 is more specific and ambitious than Aichi Target 9 and is directly linked to GBF Target 3 (30×30 — 30% protected areas by 2030).

Other International Instruments

• International Plant Protection Convention (IPPC): Governs phytosanitary measures; prevents spread of plant pests
• IMO Ballast Water Management Convention (2004): Controls marine IAS spread through ballast water
• Nagoya Protocol: Includes provisions relevant to IAS in genetic resources context

India's Policy and Legal Framework

Wildlife Protection Act, 1972

The WPA does not have specific comprehensive provisions for IAS, but Schedule IV and V list vermin species. Amendments have been called for to explicitly address IAS threats.

Environment Protection Act, 1986

The EPA empowers the Central Government to take measures to prevent environmental damage — provides a legal basis for IAS control actions, though not IAS-specific.

Biological Diversity Act, 2002

Section 38 of the BD Act empowers the National Biodiversity Authority (NBA) to take measures to regulate and control access to biological resources, including invasive ones.

National Biodiversity Action Plan (NBSAP) 2008 and 2014

India's NBSAP lists IAS management as a priority action. India's updated NBSAP 2022 (submitted at COP15) includes IAS targets aligned with GBF Target 6.

Institutional Roles

Management Methods

1. Physical / Mechanical Control

• Manual uprooting, cutting, mowing — most common for Lantana
• Dredging for water hyacinth (used in Kerala)
• Trap and remove for animals
• Cut rootstock method identified as most cost-effective for Lantana

2. Chemical Control

• Herbicides (glyphosate for Lantana, Prosopis); regulated use required
• Risk of non-target effects and soil contamination
• Used as last resort or in combination with other methods

3. Biological Control

• Introducing natural enemies from the species' home range
• Success stories:
  • Zygogramma bicolorata (Mexican beetle) introduced against Parthenium — significant control in some areas
  • Neochetina eichhorniae and N. bruchi (weevils) used against water hyacinth in several Indian states
• Risk: Introduced biocontrol agents must be rigorously tested to prevent them becoming invasive themselves

4. Utilisation-Based Management

• Converting invasive species into a resource to incentivise removal
• Lantana furniture and handicrafts (promoted by tribal communities in forest areas)
• Water hyacinth converted to biogas, compost, handicrafts (Manipur, Kerala)

5. Early Warning and Rapid Response

• Key to preventing establishment — much cheaper than post-establishment control
• IUCN recommends national IAS alert systems and biosecurity measures at borders/ports

Success Stories and Challenges

Partial successes:

• Biological control of water hyacinth using weevils has reduced cover in some reservoirs
• Lantana furniture projects have created economic incentives for removal
• Removal of invasive rats from some Lakshadweep islands improved seabird nesting

Challenges:

• No dedicated comprehensive National IAS Strategy in India (unlike Australia, New Zealand)
• Fragmented institutional responsibility across BSI, ZSI, ICAR, MoEFCC
• Lack of complete national IAS inventory and monitoring system
• Climate change is expanding the range of many IAS — new areas becoming vulnerable
• Ornamental horticulture and aquarium trade continue to introduce new species with insufficient biosecurity

Recent Developments (2024–2026)

India's Natural Areas Losing 15,500 sq km/year to Invasive Species — 2024 Study

A major 2024 research assessment revealed that India's natural areas are losing approximately 15,500 sq km per year to invasive alien plant species. Lantana camara (native to the Americas) is the most widespread invader, infesting over 33 million hectares across India. Prosopis juliflora (Mesquite, from Central America) dominates arid and semi-arid zones, particularly in Rajasthan, Gujarat, and Tamil Nadu, displacing native grasses and shrubs.

Chromolaena odorata (Siam weed) is expanding at the fastest rate — approximately 1,988 sq km/year — threatening forest understories in Northeast India, the Andaman Islands, and the Western Ghats. Mikania micrantha (mile-a-minute weed) is severely impacting Manas National Park and other Northeast India protected areas. IUCN classifies Lantana as among the world's 100 most invasive species and among the world's 10 worst weeds.

UPSC angle: Species names (Lantana, Mikania, Prosopis, Chromolaena), their invasion rates, and economic/ecological costs are high-frequency Prelims content; the national control strategy and its challenges are Mains material.

CBD COP16 Cali 2024 — Invasive Species Target Progress

The Kunming-Montreal Global Biodiversity Framework (KMGBF) Target 6 calls for identifying pathways for invasive alien species introduction, preventing or reducing their introduction rates by at least 50% by 2030, and controlling or eradicating invasive species in priority locations. CBD COP16 in Cali (October–November 2024) reviewed progress on this target and found that most countries, including India, have made limited progress in implementing national invasive species strategies.

India submitted its NBSAP (National Biodiversity Strategies and Action Plan) at COP16, which includes commitments to strengthen biosecurity measures, develop an Invasive Alien Species database, and operationalise the National Action Plan for Control of Invasive Alien Species in Protected Areas. The Invasive Species Specialist Group (ISSG) of IUCN assists countries with technical guidance on control methods including biological control, physical removal, and chemical control.

UPSC angle: KMGBF Target 6, India's NBSAP commitments on IAS, ISSG, and the 50% reduction target are Mains GS-3 content.

Aquatic Invasive Species — Tilapia and Water Hyacinth Threat 2024

In India's freshwater ecosystems, Nile Tilapia (Oreochromis niloticus) — originally introduced for aquaculture — has become highly invasive in river systems across peninsular India, outcompeting native fish species. A 2024 assessment by the Central Inland Fisheries Research Institute (CIFRI) found Tilapia in 87 of 126 major river assessment points surveyed, displacing endemic mahseer, rohu, and other commercial species.

Water Hyacinth (Eichhornia crassipes), the world's most widespread aquatic invasive plant, continues to choke lakes and waterways across India — notably Dal Lake (Jammu and Kashmir), Vembanad Lake (Kerala, a Ramsar site), and rivers in Assam. It depletes dissolved oxygen, blocks sunlight, and disrupts fisheries and navigation. MoEFCC has supported biocontrol using weevils (Neochetina spp.) but scaling remains a challenge.

UPSC angle: Nile Tilapia in rivers, Water Hyacinth in Ramsar sites, and biocontrol approaches are Prelims data points; the policy vacuum in regulating ornamental fish and aquaculture escapes is a Mains discussion point.

Exam Strategy

• Prelims: Focus on specific species names (scientific + common), their origin, how introduced, and key impact. Memorise the global frameworks: CBD 8(h), Aichi Target 9, GBF Target 6.
• Mains (GS3): IAS questions often appear as part of biodiversity conservation or protected area management questions. Discuss pathways → impacts → policy → management in a structured way.
• High-frequency species: Lantana camara (forests), Parthenium (agriculture/health), Water hyacinth (water bodies), African catfish (rivers/aquaculture), Suckermouth catfish (recent news), Prosopis (arid regions).
• Link to current affairs: Watch for news on suckermouth catfish spreading in rivers, Nile tilapia in Western Ghats water bodies, and India's National Biodiversity Strategy updates.
• Key distinction: Not all alien species are invasive — only those that cause harm. Many crops (rice, wheat) are technically alien but beneficial.

Previous Year Questions (PYQs)

Prelims

• With reference to the management of minor minerals in India, consider the following statements: ... (IAS context questions)
• Which of the following is/are invasive alien species in India? 1. Lantana camara 2. Eichhornia crassipes 3. Mikania micrantha — (All three are invasive — frequently tested)
• The term "Sucker fish" or "Janitor fish" recently seen in news refers to which species? (Suckermouth armoured catfish / Pterygoplichthys)

Mains

• What is meant by Invasive Alien Species? Explain the pathways through which they spread in India and discuss the measures taken by India to address this challenge. (GS3 2022 style)
• How does the Kunming-Montreal Global Biodiversity Framework address the threat of Invasive Alien Species? Examine India's obligations and policy response. (GS3)
• Discuss the ecological and economic impacts of Water hyacinth on India's aquatic ecosystems. What management approaches have been tried? (GS3)