Out of Control: India’s Bioinvasion Dilemma and the Way Out

People will understand the invasive species crisis much better when they know what it is costing them, says ecologist Alok Bang.


Alok Bang will never forget the panic of finding out that his sample of Argentine ants had fled its enclosure and proceeded to invade Paris. He will also not forget the relief on waking up in his hotel bed, only to realise that it was just a dream. That hotel bed was not in Paris, though. It was in the South of France. 

But when Bang rushed to his desk to check on the sample, he froze when he realised that the ants had actually escaped. Luckily, the insects had not marched to Paris. The staff at the hotel, well acquainted with the dreaded hyper-invasive species, had swiftly eradicated them before the slightest chance of infestation.

Nearly 10 years later, Bang is still stumped by his apparent premonition’. I don’t know how to explain it, but sometimes when you’re so consumed by research, the boundaries between the real and unreal blur,” says the biology faculty member at Azim Premji University, with a chuckle. 

At the time of the nightmare, Bang was a postdoctoral researcher studying invasion ecology at the University of Paris. He had travelled to the South of France to collect Argentine ants because the species had still not spread past the coastline to inland cities such as Paris.

Native to South America, Argentine ants (Linepithema humile) have now invaded all continents barring Antarctica. The International Union for Conservation of Nature (IUCN) has listed them among the 100 of the worst invasive species” on Earth. 

No species exists in isolation. They have relationships with their environment — rainfall, temperature, other species… Invasive species are able to break away from these relationships that have formed over millennia. They are somehow able to come to a new environment and form new processes, new partners, new alliances over just a few decades!”

  • A low cost experimental set up

    A low-cost experimental set-up by Bang for the study of Argentine ants. The dreaded invasive species has spread to all continents barring Antarctica.
    Credit: Alok Bang

So what enables this ant species to be so destructive, especially when the remaining 14,000-odd other species prefer to stick to their own habitats? These are the kind of questions that excite invasion ecologists like Bang.

No species exists in isolation. They have relationships with their environment — rainfall, temperature, other species… Invasive species are able to break away from these relationships that have formed over millennia,” explains Bang. They are somehow able to come to a new environment and form new processes, new partners, new alliances over just a few decades! How does this happen ecologically?”

Threat of alien invasive species

Bang explains that most species find it hard to survive in alien geographies when transported there purposefully or inadvertently via transportation, tourism or trade. Some can manage, with the right care — these include exotic vegetables and fruits cultivated in India. A few, however, manage to flourish even without human supervision.

  • Invasive species

    Clockwise from the top left corner: Lantana (Lantana camara), Carrot grass or Congress grass (Parthenium hysterophorus), Yellow fever mosquito (Aedes aegypti), and Giant African land snail (Lissachatina fulica), four of the worst invasive species in India, impacting diverse sectors such as the environment, agriculture, and health. However, their economic impacts have been only recently calculated.
    Credit: Wikimedia Commons

In fact, these few species perform so well that they take over the landscapes new to them and disrupt the ecological balance, even leading to the extinction of indigenous species. These are the ones we term as invasive’, the ones we need to worry about. Argentine ants fall under this category,” says Bang.

The ecological impact of invasive species is enormous. The spread of the invasive bush Lantana camara illustrates this well. According to an assessment by the Wildlife Institute of India, it has spread across 44% of India’s tiger reserves. It is taking over native plants that are foraged by herbivores such as deer, which in turn make up the diet of larger carnivores such as tigers. Globally, invasive species are now known to be the primary cause of plant and animal extinctions over the past 500 years.

  • Alok during field work in a remote forest

    Bang during fieldwork on invasive and native insect and vegetation in a forest of Melghat, Maharashtra. The yellow patches are sticky traps used to collect insects.
    Credit: Alok Bang

Surely, this is enough to make governments act. Not quite. While studying the ecological impact of invasive species, Bang quickly realised an unpleasant truth: You can cry yourself hoarse for years about conservation issues and biodiversity, but nothing gets registered. There is a need to talk in terms of language that people, especially policymakers, understand.”

One language that policymakers understand is that of economics. Most people don’t care so much about the loss of a species, but they will immediately wake up if you start talking about annual costs.” 

By the time he joined the lab in Paris, his postdoctoral advisor Franck Courchamp had already begun work on this line. Over the next few years, Bang and Courchamp collaborated with over 100 ecologists and a few economists from all over the world to brainstorm on the need to supplement the existing dialogue on invasive alien species (IAS) with data on the monetary loss being incurred.

While economic development and environmental conservation are often seen as two opposing sides of the development spectrum, quantifying the costs borne by a country due to invasions could be an effective way to attract the attention of policymakers and motivate measures against IAS,” Bang wrote in a paper resulting from their studies that was published in the journal Biological Invasions in 2022.

Bang was the first author of this paper, which used a global database to evaluate the economic cost of biological invasions in India. The study revealed some mind-boggling numbers: IAS have cost the Indian economy at least INR 8.3 trillion to 11.9 trillion between 1960 – 2020 (about USD 127 to 182 billion, by 2017 currency exchange rates), the cost has only increased with time.

Extent of damage

The authors explain that the annual estimated cost of INR 0.13 trillion (US$ 2.1 billion, which, over the last 60 years, adds up to US$ 127 billion) is 5 – 10 times more than India’s 2021 – 22’s allocated budget for the Ministry of Environment, Forestry and Climate Change.

Another, and equally alarming, way of looking at it is: the average annual IAS cost estimate of INR 0.13 trillion (USD 2.1 billion) in India is higher than the national GDPs of 25 of the world’s smallest economies.

  • India Map DM added INR- invasive species- cost incurred

    Regional distribution of biological invasion costs incurred in India. Note that the costs in brackets are percentages of regional costs. Four regions have no documented cost entries (i.e., designated as NA) in the authors’ dataset.
    Credit: Alok Bang

The group also highlighted that India ends up losing much more money on bioinvasion-related damages than what it spends on preventing or managing the spread of IAS. This is what sets it apart from high-income economies such as the US, Europe and Australia that mobilise massive efforts and investments towards managing these species. These are reflected in the stringent biosecurity laws controlling the species that are introduced and grown in these countries.

Whereas here in South Asia, places are more open… any species could escape, walk out or fly out and establish itself. Most invasive species start their populations close to ports and airports, where most of the traffic is coming in,” Bang explains.

A data deficit dilemma

Acute data deficiency is one of the biggest setbacks for India in its struggle to manage the bioinvasion crisis. According to Bang, India is home to more than 1,500 recorded alien species, however, only 330 of these have been termed invasive.

This is not because the rest are not invasive but because we haven’t worked on them enough to term them as such,” he points out.

According to Bang, India is home to

  • 1500 + recorded alien species
  • 330 termed invasive

At just one-sixth the landmass, France has about 2700 alien species. It is inconceivable that India has so little. This immediately reflects on the cost, so there’s a huge gap in terms of how much we know. Generating this data will be the first step.”

  • Cost distribution of IAS in India (a)

    (a) Showing the number of specific plant (green) and animal (purple – blue) costs recorded against the total number of invasive alien plants and animals present in India (grey)

  • Cost distribution of IAS in India (b)

    (b) Breakdown of cost by species from 1960 to 2020. Green bars represent plant costs and purple – blue bars represent animal costs.

Costs are in million USD (2017 value).
Note that despite only a very small proportion of known invasive species in India have associated costs, these costs are massive.
Credit: Biological Invasions

This is also the lens through which a newer study published in Nature Sustainability this May, is to be viewed. While this one also relied on the global database of bioinvasion records to evaluate economic impact, it ranked continents as origins (sources of IAS costs) or recipients (destinations of IAS costs). The results of the study suggest that most economically damaging invasive species originate in Asia, and the worst affected is North America. 

While India was not identified as a top receiver of invasive species, it was ranked second among the senders, in between China and Mexico. This might imply that India is more of a perpetrator than a victim when it comes to bioinvasion. However, this would be a misguided takeaway, asserts Bang who was also a part of this international study. 

At least 75% of the data on reported costs were from the US or Europe. If we had really good data, the results could be different. India and China wouldn’t necessarily be the only source countries and Europe and North America be the only sink,” he predicts. 

  • Alok world map top left- bioinvasion story

    (a) Reported routes of the flow of invasive alien species. Arrow thickness indicates the number of species. Arrows indicate species’ known native ranges and final recipient regions of reported costs (coloured by sender continent) and therefore do not necessarily indicate direct flows between continents.

  • Alok world map bottom right

    (b) Depiction of the non-uniformity in the distribution of studies in the dataset.

Note that records suggest that the largest continents are the least costly ones. This is an obvious problem, a symptom of data deficiency in the Global South.
Credit: Nature Sustainability

Yet, Bang maintains that this is an important study because it establishes once again that geopolitical borders mean little to global environmental issues such as bioinvasion. 

He elaborates: The trade, transport and tourism routes interconnecting the world are not one-way routes, right? What is going from India or China to the US is also travelling back. So there’s always a possibility that certain microbes, plants, seeds, insect larvae, can travel to India from these places. It is just that they are not being documented. The overarching message is that these routes exist, and they do not obey any order.” 

India’s best bet at controlling bioinvasion would be to instate a national biological invasion research programme, Bang and his co-authors wrote in their 2022 paper. Though centrally funded, such a programme would need regional offices with management strategies reflecting local scenarios. This is important, says Bang. Having only a national policy to tackle — say, lantana— is not useful, because each species is evolving in response to the local conditions. So, a mechanism to control lantana in Bengaluru may not work in the Himalayas,” he adds.

  • Lantana being managed by uprooting

    Lantana being managed by uprooting
    Credit: Rajat Rastogi/​Mongabay India

As determined as Bang is to save India from alien invasive species, he admits that all this focus on the evil’ side of nature takes a toll on him. You see, my reason for getting into ecology was a love for the living world. It so happens that in this field [of invasion ecology], some species are looked upon as problematic,” he says. 

But instead of letting the disillusionment fester, Bang has a plan to stay positive. I plan supplement my work with something very native which has nothing to do with invasion. So if I am working on an invasive ant, I would like to supplement that with a local ant in a local ecosystem — just to not be in that negative zone all the time,” he explains.

Bang is set to have many opportunities to strike this balance with his move to Azim Premji University, Bhopal. He looks forward to studying the relatively under-explored and undisturbed natural landscapes of Central India with his students.

Everyone wants to go to the Himalayas or the Western Ghats but the dry deciduous forests of Central India that constitute about 40% of India’s forests remain largely ignored. These are also the areas where the first batch of rights on forest entitlement and usage have been given to forest-dwelling communities under the Forest Rights Act, thereby making it a very interesting socio-ecological space to investigate questions on the crossroads of basic and applied ecology. If the forest department permits, we can do some interesting research in the various nature reserves in and around Bhopal.”

No more ant apocalypse nightmares for this ecologist, please! 

About Alok

Alok Bang is a faculty member at Azim Premji University, Bhopal.

About the author

Nandita Jayaraj is a science writer and communications consultant at Azim Premji University. She may be contacted at nandita.​jayaraj@​apu.​edu.​in

Published on 10 August 2023