At least 241 invasive plants mapped in 7 South Asian countries; India tops list
India, with its largest land area in the group of seven countries in South Asia, tops the list with 185 invasive alien plants
Scientists from India and six other countries have come up with an inventory of 241 plants, which were introduced in south Asian countries and have over the years become Invasive Alien Species (IAS). India tops the list with 185 such plant species.
“This is the first such attempt to come up with an integrated inventory of invasive alien flora of South Asia. European countries have already come up with such a database. Of late, an integrated alien species inventory for the Central American region comprising seven countries has also been assembled,” said Anzar A Khuroo, associate professor of Botany at University of Kashmir and a senior author of the team.
IAS are animals and plants that are introduced into places outside their natural range, negatively impacting native biodiversity, ecosystem services or human well-being. They are one of the biggest threats to biodiversity and are also a global threat to food security.
While India, with its largest land area in the group of seven countries, tops the list with 185 invasive alien plants listed by the team, it is closely followed by Bhutan with 53 such plants, Sri Lanka with 45 and Bangladesh with 39. Maldives has the lowest invasive plants with just 15 species. Nepal has 30 and Pakistan has 29 such invasive alien plant species.
The findings have been published in peer-reviewed journal ‘Biological Invasions’ in its September 2023 issue. Researchers from India, Pakistan, Bangladesh, Australia, Nepal, Bhutan and Sri Lanka took part in the study. From India, researchers from University of Kashmir, National Remote Sensing Centre and Kerala Forest Research Institute were present as members.
It was found that Southern America was the major contributor, both at the country level and across the region, thereby indicating that the tropical climate matching aids in the establishment and spread of alien species.
The highest number of invasive plants were introduced in south Asia from Southern America (142), followed by Northern America (66), Africa (42) and Europe. The results also show that around 40% of the plants were introduced by chance through the escape pathway. Around 24% came as stowaway, such as in ballast water of ships, and around 21% were released.
“The findings have immense implications. Now that we know southern America was the major contributor of IAS, both at country level and across the region, thereby indicating that the tropical climate matching aids in the establishment and spread of alien species, we need to be extra cautious while dealing with plants coming from there more than those coming from Europe,” he added.
The scientists found that one plant — ‘Lantana camara’ — which is a native of south and central America and was introduced by the British in this part, is now invasive in all the seven countries in South Asia. Likewise, three species — Parthenium hysterophorus, Pontederia crassipes and Leucaena leucocephala — were found to have become invasive in six countries. Two other species — Ageratum conyzoides and Sphagneticola trilobata — were distributed in at least five countries. At least 150 plant species of the 241 identified were still restricted to a single country.
IAS are compounded by climate change. Climate change facilitates the spread and establishment of many alien species and creates new opportunities for them to become invasive.
They can reduce the resilience of natural habitats, agricultural systems and urban areas to climate change. Conversely, climate change reduces the resilience of habitats to biological invasions, security and livelihoods.
An earlier research finding by a separate team of international scientists had found that IAS have cost the Indian economy between at least ₹8.3 trillion to ₹11.9 trillion (US$ 127.3 billion to 182.6 billion) over 1960–2020, and these costs have increased with time. This finding was published in a Springer journal in April 2022.
Out of the 241 species listed, at least 236 were angiopsperms (flowering plants). There were three gymnosperms (seed producing plants like pine tree) and two pteridophytes.
The plant family, which accounts for the highest number of invasive species, in the region is Asteraceae. Plants like sunflower, marigold, dahlia, dandelion and lettuce come from this family. At least 156 plants from this family are in the invasive list. It is followed by families like Fabaceae (36) and Solanaceae (18). The genera Acacia has the highest invasive species.
The vilayti kikar (Prosopis juliflora) which is found in Delhi belongs to the family Fabaceae. The genera, which has the highest invasive plant species, is Acacia.
The invasive plants of south Asia consist of 156 perennials (65%), 82 annuals (34%) and 3 biennials (1%). In terms of growth form, most of the invasive species were herbs (146), followed by shrubs (38), trees (30), climbers (20), subshrubs (4) and vines (3).
“This study would foster further research in those areas of south Asian countries where data of invasive plants and animals are deficient. The Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) has recently published a report enlisting more than 37,000 alien species which have been introduced to regions and biomes around the world as a result of various human activities. But there too there was a gap in data fed from south Asia and Africa,” said said Ruquia Gulzar, lead author of the study from University of Kashmir.
Target 6 of the Kunming-Montreal Global Biodiversity Framework, agreed at the 15th meeting of the Conference of Parties to the UN Convention on Biological Diversity, also speaks of reducing the impacts of IAS on biodiversity and ecosystem by at least 50 percent, by 2030.