- A survey documents the naturalisation of African Bermuda-grass, native to Central and East Africa, in two Indian biodiversity hotspots, the Himalayas and the Western Ghats.
- The study shows how delays in identifying biological invasions can hinder management of invasive species and allow them to spread unchecked.
- It also highlights gaps in infrastructure and policy and suggests that early intervention is the most effective way to limit the potentially high economic costs of biological invasions.
An alien surprise was waiting for Kuntal Saha, a taxonomist from the Forest Research Institute, Dehradun, when he spotted some grass after stepping down from his vehicle near Tangmarg, a scenic town in the Baramulla District of Jammu and Kashmir in 2023. “It was my first visit to Kashmir. I was simply enjoying the breathtaking scenery when I noticed an unfamiliar Cynodon population growing along the roadside, says Saha, adding that they had earlier seen the grass species near the houseboat where they were staying in Srinagar.
Grasses of the genus Cynodon are valued for their use as fodder and in developing turf for lawns. The genus also includes a sacred grass (Cynodon dactylon) called doob, durba, dubari etc. in Indian regional languages.
Saha, however, spotted something distinct and this eventually became one of the most important collections of their field trip in 2023, part of a decades-long survey which began in 1995 when Saha’s mentor, Indian Forest Service Officer Manoj Chandran (now retired), collected an unknown Cynodon species from Tamil Nadu during his botanical explorations.
“At that time, the specimen could not be fully appreciated because of its close resemblance to other Cynodon species,” explains Saha. Over the years, they kept collecting specimens across Tamil Nadu, Kerala, Uttarakhand and Jammu and Kashmir. Based on this survey, the researchers recently reported that Cynodon nlemfuensis, the African Bermuda grass, which is native to Central and East Africa and introduced to India, has been naturalised in the Himalayas and the Western Ghats. Naturalisation of introduced species occurs when they are able to sustain self-reproducing populations in the wild.
Systemic gaps delay identification
Consulting relevant literature and the type specimen collected from parts of what is now the Democratic Republic of Congo, in 1917-1918, they clarified the taxonomy of their sample of C. nlemfuensis and designated a representative specimen for future reference.
The representative voucher specimens (biological specimens representative of its species in accordance with the relevant taxonomic authority) submitted by them are available at the Dehra Dun Herbarium (DD) of the Forest Research Institute, India. It took them almost 30 years to report the African Bermuda-grass found in the 1995 survey. The average delay between first identification to publication of naturalised species is 27 years but can lag by over a century for some.
Ninad Avinash Mungi, a researcher specialising in biological invasions and ecosystem restoration says, “This is a timely and important study that highlights a critical but often overlooked challenge in invasion biology — the difficulty of correctly identifying lesser-known alien species.” Mungi was not associated with the study.
Mungi, currently an assistant professor at Aarhus University, Denmark, explains that many grass species are notoriously difficult to identify, especially outside the flowering season or in heavily grazed landscapes. He says that the study effectively demonstrates how taxonomic challenges can allow invasive plants to remain unnoticed for years, delaying management interventions.
Ecologist Achyut Kumar Banerjee, Assistant Professor, Azim Premji University, Bhopal, a co-founder of Indian Alien Flora Information Database (ILORA) says, “ILORA version 2 is working on this front [quicker identification of invasive species].” He notes that they face identification issues in ILORA, especially for grasses, as in most cases, the type specimens [of identified plant species] for comparison, are not available in India. “They are available in some herbaria abroad as was in Belgium for this study. The Indian herbaria, both national like the Central National Herbarium (CNH), and regional ones, often lack digitised collections.”
He notes that although CNH is making its digitised collections available very recently, the general lack of handy information about plant identification in the country makes the task of cross-checking new collections against type specimens difficult and this delays any monitoring or management response for alien species.
Banerjee, who was not associated with Saha’s study, says it serves as a template for how novel naturalisation records should be documented — with voucher specimens, precise coordinates, and resolved taxonomy — instead of a casual occurrence record. He reminds that such taxonomic rigour matters because misidentification is itself a major reason invasive grasses go unmanaged for years.
However, he stresses that herbarium digitisation and taxonomic capacity-building should not be treated as a purely academic pursuit, but be integrated tightly into invasion biosecurity infrastructure.
Poor surveillance facilitates naturalisation
Alien or non-native plant species introduced to a particular landscape face unfamiliar and diverse biotic and environmental barriers. Most of these species fail to adapt to such conditions, but some manage to overcome those and survive and thrive. Some remain ‘casual aliens’ — do not establish a self-sustaining population — while some adapt well enough to become naturalised, capable of reproducing without human intervention. Invasion requires naturalisation followed by successful propagation, and in the course of these events, an alien plant may gradually become an invader that changes the local ecosystem with potential impacts.
The economic cost of biological invasion in India was estimated to be between $127-182 billion over 1960–2020. The lead author of the study published in 2022, invasion biologist Alok Bang, Assistant Professor at Azim Premji University, Bhopal says that plant invasion is often discussed in terms of introduction, establishment and spread, but an equally important stage is policy and institutional recognition. “A species cannot be managed until it is detected and communicated to the relevant authorities,” he comments.
Pointing out the problematic scenario of an invader with economic potential (as Bermuda grass is useful as fodder), Bang says, “If a species is economically more beneficial, it does not justify its introduction. Benefits usually come from private or individual endeavours such as agriculture or industries, and costs usually occur in the domain of the commons, such as air, water, soil, and biodiversity. Intentional species introductions and establishments ultimately lead to privatisation of benefits and socialisation of costs.”
“Discovering an African grass in the cool temperate climate of Kashmir and Uttarakhand was especially exciting because it demonstrated the remarkable ecological adaptability of the species compared with its occurrence in warmer regions such as Tamil Nadu and Kerala,” says Saha.
The authors of the recent study spotted the African Bermuda-grass on the roadsides of national highways, open grasslands, and other anthropogenically disturbed habitats with less disturbance and competition from native flora. Using these invasion corridors fortified by tourism, climate change and infrastructure development projects around the country, the authors note the risk of its spread into Central India, into the Himalayan highlands, and neighbouring countries. They also remind of the grave ecological consequences of its spread into cropland and pastures requiring extensive control measures.
Banerjee says that as the species was found colonising roadsides and disturbed grasslands, it’s still at an early, localised stage rather than a landscape-scale infestation. “That’s exactly the time when the Early Detection and Rapid Response strategy is most effective to manage an invasive species,” he comments.
Need for effective policies and research
Complicated by anthropogenic influence and climate change, biological invasions can endanger regional biosecurity and cause heavy financial damages to agriculture, forestry and fisheries.
Bang says, “Everyone agrees that early detection of invasive species is desirable.” Knowing that delaying detection and response often results in substantially greater long-term economic losses, Bang emphasises investing in developing effective surveillance systems and making it an integral part of policies.
Considering African Bermuda-grass, a known invader globally, he says that this study demonstrates that India also lacks robust preventive mechanisms for species whose invasive potential has already been documented internationally. According to Bang, policies must also be built around invasion hotspots which include both biodiversity hotspots and areas bustling with human activity such as commercial sectors, especially live animal and plant-based industries, around transport avenues, and places with heavy tourism.
Nearly 66% of India’s natural ecosystems are threatened by invasive plants, emphasises Mungi, adding that addressing biological invasion requires a systematic and interdisciplinary approach that combines foundational tools like taxonomy, long-term field ecology and citizen science with the advantage of high throughput technologies such as remote sensing, molecular tools, particularly for aquatic ecosystems and AI-assisted species identification including screening of plants in horticultural trade. He also mentions the need for involving all the stakeholders by ensuring active participation from sectors such as agriculture, forestry, animal husbandry, local communities, and researchers.
However, according to Mungi, a major gap in India is the absence of a dedicated organisation or even institutional framework for invasive species research and management. “Responsibilities are currently dispersed across multiple organisations, making it difficult to coordinate surveillance, research, policy, and restoration efforts,” he comments, echoing Bang.
This long term study was not funded by any specific grant. Saha mentions, “Much of the work relied on personal commitment, long-term collaboration, institutional support, and extensive field exploration rather than dedicated research funding.”
Bang notes, “Taxonomy is the foundation of almost every biological discipline, but especially so in applied ecology. Despite this need, not just in academia, but in national biodiversity policies, taxonomy has declined as a career choice. An effective policy around invasives therefore must have an in-built mechanism to address this shrinkage of experts.”
Banner image: Kuntal Saha, lead author of the study spots Cynodon nlemfuensis on a field trip in the Kashmir Himalaya, near Gulmarg. Image courtesy of Kuntal Saha.
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