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New study finds invasive alien plants expanding across 15,500 km² of India’s natural areas every year.
144 million people and large areas of farmland and wildlife habitat already exposed to invasions.
Species such as Lantana camara, Chromolaena odorata and Prosopis juliflora now dominate two-thirds of natural ecosystems.
Invasions accelerating due to climate change, land-use shifts, altered fire regimes and biodiversity loss.
Invasive alien plants are transforming India’s natural ecosystems at an accelerating pace and have nearly doubled their range in ecologically sensitive regions such as the Western Ghats, the Himalayas and the north-east, scientists have warned.
Their rapid spread is being driven by the combined pressures of climate change, land-use change and widespread biodiversity disruption, according to a new study published in the journal Nature Sustainability.
Researchers say the expanding footprint of these species is creating severe socio-ecological risks and threatening the livelihoods of millions of people who depend directly on nature.
The study estimates that by 2022, nearly 144 million people, 2.79 million livestock and 200,000 square kilometres (sq km) of smallholder agricultural land had been exposed to at least one new plant invasion.
The authors assessed 16 years of systematic monitoring, covering 277,000 sq km across India between 2006 and 2022, to examine how plant invasions intersect with global environmental changes such as warming, altered fire regimes, shifts in herbivory and rapid land-use transformation.
“Annually, ~15,500 km² natural areas are invaded by at least one new species, exposing ~11,200 km² of herbivore occupancy to forage loss. Every year almost 7 million people have been exposed to new invasive plants in the last two decades,” the researchers wrote in their paper.
By 2022, invasions had affected 266,954 sq km of natural areas containing abundant native forage for livestock and wild herbivores, 212,450 sq km of wild herbivore-occupied landscapes, and 105,725 sq km of tiger habitat.
Almost two-thirds of India’s natural ecosystems now contain at least 11 major invasive plant species, including Lantana camara, Chromolaena odorata and Prosopis juliflora.
The study compiled 1.06 million records of alien plants collected over the 16-year period. Chromolaena odorata was found to be expanding fastest, spreading at a rate of 1,988 sq km per year.
In the Western Ghats and the north-east, the species has almost doubled its range within two decades. In India’s dry regions, Prosopis juliflora, introduced historically to prevent desertification, has spread across entire landscapes, displacing native shrubs and grasses essential for wildlife and pastoral communities, the findings of the report stated.
Some species previously thought to be confined to arid environments have now moved into Himalayan regions and wet evergreen forests. Open natural ecosystems such as the dry grasslands of peninsular India, wet grasslands along the Ganga and Brahmaputra, shola grasslands in the Western Ghats and savannas across the country were identified as the most vulnerable.
“At current rates, entire ecosystems could shift from native to invasive dominance within a generation,” said lead author Ninad Mungi in a statement adding, “These plants are moving faster than we can manage or even monitor them.”
The study categorised invasive species by biome affinity, showing distinct responses to environmental changes like changing soil moisture, livestock grazing, and fire regime.
Wet-biome invaders such as Ageratina adenophora, Chromolaena odorata and Mikania micrantha expanded with increasing fire frequency, declining soil moisture and rising temperatures, the researchers stated.
“Conversely, dry biomes invasions (e.g., Prosopis juliflora (syn. Neltuma juliflora) and Xanthium strumarium) increased with declining fire frequency, increasing soil moisture, increasing livestock grazing, and increasing rainfall,” the paper observed.
The researchers identified 243 sub-districts and 167 protected areas as being at high risk, and therefore priorities for intervention. Lantana camara emerged as the most dominant invader in most states, while Chromolaena odorata was identified as the fastest-growing threat. High-risk clusters were mapped in the Shivalik-Terai belt in the north, the Duars in the north-east, the Aravalli ranges, the Dandakaranya forests in central India, and the Nilgiri region of the Western Ghats.
The study assessed how invasions are affecting agro-pastoral areas and traditional livelihoods, often forcing communities to migrate.
India’s economic losses from invasive species between 1960 and 2020 are estimated at $127.3 billion (Rs 8,30,000 crore). The study noted that the invasion crisis is being accelerated by broader environmental disruptions including habitat fragmentation, land-use change, sporadic wildfires and climate change.
Wet-habitat invaders are being aided by warming temperatures and more frequent fires, while dry-habitat invaders are benefiting from higher rainfall and declining fire regimes.
“This convergence means invasions can no longer be treated as isolated ecological problems. They are symptoms of deeper systemic disruptions, of how we manage land, water, and development”, said co-author of the paper Jens-Christian Svenning.
For many rural and pastoral households, the consequences are immediate and tangible. Invasive plants reduce fodder and fuelwood availability, deplete soil fertility and can even trigger respiratory illnesses.
“For rural and pastoral communities, invasive plants reduce fodder and fuelwood, lower soil fertility, and even trigger respiratory ailments. Every hectare lost to invasive plants translates to lost income, nutrition, and resilience. Poverty, in turn, limits the capacity to act, trapping communities into a cycle of ecological and economic vulnerability,” the study said.
Species like Prosopis juliflora often block access to pasture, firewood and water, forcing marginalised households to travel further for daily necessities.
“If we fail to manage them, we risk losing biodiversity, livelihoods and the fragile balance of coexistence,” said YV Jhala, a contributor to the study.
Despite being one of the world’s invasion hotspots, India lacks a dedicated institutional mechanism or a national database of successful management practices, the researchers argue.
“The result is a policy landscape resembling a patchwork of intentions rather than a cohesive strategy,” said co-author of the study Qamar Qureshi.
The authors call for the creation of a National Invasive Species Mission to integrate scientific monitoring, evidence-based management, improved quarantine systems, inter-sectoral coordination and strategic financing.
“Such a mission can integrate invasion control into climate adaptation, poverty alleviation, and restoration programs,” Mungi added.