Nearly half of India vulnerable to alien invasive plant species: Study

Nearly half of India's total geographical area is prone to invasion by alien plant species, says a new study. It shows that biodiversity hotspots in India are "especially vulnerable" and limiting human interference in remote forests is necessary.

Scientists from North-Eastern Hill University (NEHU), Shillong, have created the first pan-India catalogue of regions most susceptible to invasion and identified the 'hotspots'.

'Hotspots' are regions that are climatically and geographically most suited for alien invasive species - species which colonise, spread and invade new territories.

"Almost half of the total geographical area of India is prone to invasion by alien plant species with moderate and high levels of climatic suitability," Saroj K. Barik, co-author of the study and a professor at the Centre for Advanced Studies in Botany, NEHU, told IANS.

In India, alien plant species constitute 40 percent of the total plant diversity, of which 25 percent are invasive (such as Siam weed, bitter vine, water hyacinth and mesquite).

Alien invasive species threaten the biodiversity hotspots, he said.

Key findings show most ecologically sensitive regions of India, including the biodiversity hotspots, islands, coastal forests, freshwater swamp forests, mangroves and protected forest reserves, croplands, rangelands and village biomes coincide with the identified 'invasion hotspots', indicating their vulnerability to alien plant invasion.

Barik said more than half of the geographical areas of Andaman and Nicobar Islands, Andhra Pradesh, Assam, Dadra and Nagar Haveli, Daman and Diu, Goa, Kerala, Manipur, Meghalaya, Mizoram, Nagaland, Odisha, Pondicherry, Tamil Nadu, Tripura and West Bengal are at "high risk" of being invaded by alien plant species.

Some of the major port towns such as Mumbai, Ratnagiri, Panaji, Nagapattnam, Chennai, Kakinada, Paradip, and Haldia fall within the identified invasion hotspots. Such areas provide suitable habitats for colonisation of alien invasive species after being introduced through shipping routes.

The study (using modelling and GIS data), carried out by Barik, D. Adhikari and R. Tiwary of NEHU is published in 'PLoS One' journal and contributes to the comparatively little studied genre of ecological invasion.

Additionally, it sheds light on the fact that remote forest areas with high tree cover and low human population are "unlikely" to be invasion hotspots. This stresses on the necessity of minimum human interference, said Barik.

"Delineating the areas climatically suitable for invasion by diverse species would enable us to gauge the extent of damage the invasive plants can incur to the native biodiversity, assist to identify areas threatened by invasion and facilitate formulation of appropriate policy for their control and management," said Barik.

Worldwide, alien invasive species cause an estimated annual economic loss of $314 billion in the agriculture and forestry sectors, of which India's share is around $116 billion.