Know about India’s top invasive plant species

Climate change will worsen the spread of invasive species that tend to show strong resistance to warming and spread across landscapes, scientists report.

A team from the Forest Productivity Institute, Ranchi, analyzed the dispersal dynamics of two invasive plant species, Chromolaena odorata and Lantana camara. The researchers used computer models to examine the present and future (2050) distribution of the two plants in central and eastern India.

Nuisance weed

The study area included Jharkhand, Chhattisgarh and West Bengal. Their results, that the two plants showed strong resistance to climate change, provide valuable information on sensitive sites prone to future invasions. This prior information helps develop prevention and control measures to contain the infestation.

“These robust plants can also adapt and expand in various climatic and environmental scenarios,” says Tiwari, whose team previously modelled the potential risk zone of Lantana camara invasion and response to climate change in eastern India.

There are no precise estimates of the total area affected, but "wherever you go, you can witness their distribution," he adds. "Areas that have a combination of sun and moisture are best suited for these invaders, hence their wide distribution in Goa, Jharkhand and southern India."

Transport, especially in tourist hotspots like Goa, along with wind, birds, and bushfires, drive the spread of invasive species that spread mainly along roads, agricultural fields, and natural landscapes.

How many invaders have been recorded in India?

Although there is confusion regarding the exact number, there are thought to be over 200 invasive species in India (a 2017 study lists India as one of the regions with the most invasive flora in the world).

• Water hyacinth (Eichhornia crassipes)

• West Indian lantana (Lantana camara)

• Carrot grass (Parthenium hysterophorus)

• Siam weed (Chromolaena odorata)

• Wild tamarind (Leucaena leucocephala)

• American rope (Mikania micrantha)

• Black wattle (Acacia mearnsii)

• Mesquite (Prosopis juliflora)

• Crofton weed (Argentina adenophora)

• Giant sensitive plant (Mimosa pigra)

unwanted superfluous flora

Invasive plant species are unwanted superfluous flora that causes unfavourable changes in the expansion potential of the native vegetation composition of a large region.

These invasive species are very expansive due to their propensity to produce large numbers of viable seeds long-term in the soil. These are native to one place, influencing composition and environment by spreading prolifically, and becoming alien when introduced to places other than their native region.

The invasion of invasive flora into newer territories by endemic species is one of the most serious threats to floral diversity after the main problem of habitat loss. The passage of a species beyond its natural limits contributes to the alteration of the distribution of biodiversity.

According to the Global Invasive Species Database (2021), Chromolaena odorata and Lantana camara are among the 100 most serious invasive alien plant species. They mostly invade grasslands, croplands, horticultural lands, and open woodlands.

Control options

Scientists are also exploring other options. It is virtually impossible to completely control or eradicate invasive species, Tiwari said. "We can, however, initiate interventions by area to restrict their spread in eco-sensitive areas and other similar priority areas."

Usually, control measures such as chemical, mechanical and natural are proposed, but Tiwari prefer and advocates the promotion of flora based on native species to address the invasion. “My experience shows that virgin forests or forests that have a dense canopy do not allow invaders to enter their area,” he said.

“Burning is another option,” Ranjan added. "Lantana, in particular, is very expensive to uproot, and uprooting results in more vigorous growth."

For Bang, the best solution is to have strict biosecurity policies at the national and regional levels to prevent any exotic or exotic species from entering the country. "India has a very weak biosecurity policy at the moment," he said.

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