Invasive alien species of India

Prelims and MainsCurrent affairs on this: Invasive alien species

An alien species is one moved by people beyond its natural range; it becomes invasive when it spreads on its own and harms the species, ecosystems or economies it enters. India's worst invaders were invited. Lantana came as a garden ornamental in the nineteenth century and now covers forest floors from the Himalaya to the Western Ghats; Prosopis juliflora was planted for fuelwood in the drylands and has taken over grasslands and wetlands; water hyacinth was brought as an ornament and chokes lakes and rivers; Parthenium arrived in wheat imports in the 1950s and causes dermatitis and crop loss; Mikania, mile a minute weed, smothers forests in the Northeast. In water, the African catfish and tilapia outcompete native fish. The Wildlife (Protection) Amendment Act, 2022 gave the Centre its first power, in Section 62A, to regulate or prohibit the import, trade, possession and spread of invasive alien species.

• Why they win: no natural enemies in the new range, fast growth and seed output, tolerance of disturbance, and often chemicals that suppress neighbours (allelopathy), as with Lantana and Parthenium.
• What they cost: lost grazing and forest regeneration, blocked waterways, fisheries collapse, and health effects; they are among the top five causes of biodiversity loss in the assessments of the Intergovernmental Science Policy Platform on Biodiversity and Ecosystem Services (IPBES).
• Control is hard and never finished: mechanical uprooting, biological control with a host specific insect (the Mexican beetle Zygogramma on Parthenium), and use as a resource (Lantana furniture, Prosopis charcoal) are the three routes.
• Marine and island cases: rats and goats on islands, the lionfish in the Atlantic, and ballast water moving species between ports, which the Ballast Water Management Convention addresses.
• The 2022 amendment's Section 62A adds India's first national handle; before it, invasives were managed by State forest departments without a listing mechanism.

Mains: Invasive species are a governance failure before they are an ecological one: each arrived through a decision to introduce it, and the cost of removal now exceeds the benefit that justified it.

Further reading: Invasive alien species (CBD) · Invasive alien species and sustainable development (IUCN)

See also: The Great Indian Bustard · National Management Plan of Invasive Species · Keystone, umbrella, flagship, indicator: the species concepts