When Ramya Ravi first visited the Banni grasslands in Kutch, Gujarat, the Ph.D. scholar at the Ashoka Trust For Research In Ecology And The Environment (ATREE) hoped to understand the impacts of the invasive tree species Prosopis juliflora on the local ecosystem.

Native to South America, P. juliflora (Prosopis or Mesquite) was introduced into the Indian subcontinent in 1877 as a source of fuelwood, fodder, and shelter. Sturdy, disease- and drought-tolerant, Prosopis thrived in arid environments and soon spread across the country, staking claim in new territories. A 2017 map published by researchers at the Centre for Pollution Control & Environmental Engineering, Pondicherry University, showed its presence in all Indian states except for a few in the eastern and northern parts of the country.

Ravi had set out to discover how the resident Maldharis, pastoralist communities that make their living by selling dairy, had been negatively affected by Prosopis trees setting up camp alongside the native fodder species in the Banni grasslands. Over the years, her findings revealed a complex picture.

“Multiple smaller communities make up the pastoral identity of the Maldharis, and their response to invasion also varied. For some, Prosopis provided a vital source of income through charcoal making during lean months and periods of poor rainfall,” she said.

Through her interactions and ensuing research, Ravi found that the impacts of invasive species on human well-being are often neglected. This discourse becomes crucial, especially in the Indian context, where many of these species play a vital role among rural and indigenous communities dependent on natural resources for survival. In a recent review, Ravi and Ankila Hiremath, Adjunct Senior Fellow at ATREE, document the diverse implications of plant invasions on human wellbeing, thus highlighting the need for contextual analysis and management of invasions.

The other side of invasive species

The conversation about invasive alien species (IAS) having positive impacts can be tricky. IAS greatly threaten ecosystems, biodiversity, and the survival of native species while costing the economy billions of dollars. A recent study has revealed that plant invasions threaten more than half of India’s natural areas.

At the time of writing this article, reports show that IAS are taking over public spaces in Bengaluru city, impacting wildlife biodiversity in the Manradiar region in Mudumalai Tiger Reserve (MTR), Tamil Nadu, and reducing food sources for wildlife in Karnataka’s Western Ghats — a few of the many examples that highlight their dangers.

In their review, Ravi and Hiremath outline instances where communities have adapted to the presence of IAS, utilising them for livelihood diversification (as seen with the Maldhari community), fuelwood, animal feed, and as sources of natural treatment alternatives. Based on 47 publications, the researchers charted the positive and negative impacts of IAS on personal safety, social and cultural uses, adequate livelihoods, and feeling well.

“Undoubtedly, a large number of IAS are harmful. But, some unique adaptations have also occurred. Through the paper, we say that instead of taking a blanket approach to managing invasive species, we need more localised analysis of people’s responses and priorities to arrive at sustainable solutions for invasion management,” said Ravi.

A world in constant overhaul

“We are seeing one of the great historical convulsions of the world’s fauna and flora,” wrote ecologist Charles Elton in his seminal 1958 book The Ecology of Invasions by Animals and Plants. In their tribute to the book, professors Anthony Ricciardi & Hugh J. MacIsaac write — “Previously, ecologists had treated invasions as anomalies. Elton characterized them as being symptomatic of a process that could alter the biological landscape of the planet.”

Following Elton’s book, the Scientific Committee on Problems of the Environment (SCOPE) programme in the mid-1980s highlighted the negative impacts of invasive species on biodiversity and natural ecosystems, kickstarting the dedicated field within ecology. “The 1990s saw a surge of studies on IAS mainly carried out by biologists. India was a few years behind and a similar uptick can be observed in India in the early 2000s,” explained Hiremath.

She further added that the pattern of looking at the overarching impacts of IAS — not just the biological impacts — is a relatively recent trend. “Economists picked up on it first, analysing the costs of [biological] invasion. In South Africa, studies then looked at the impacts of IAS on ecosystem services, adding another layer to the discourse. But the focus on the human dimensions of invasive species, such as their impacts on livelihoods, is a recent development in the field both in India and globally,” said Hiremath.

Our view of IAS informs our decisions on how we choose to manage them, explained Dov F Sax, professor of Environment and Society, Ecology, Evolution, and Organismal Biology at Brown University. “Different organisations around the world use the term somewhat differently. Sometimes, they mean a species that’s widely distributed outside its native range. Sometimes, it is a species that causes some harm to people or nature. While the usage varies, the word itself is designed to elicit a particular emotional response. No one wants to be invaded; hence, the natural response is to stop it. On the other hand, if the species is viewed as a new member of the society, the visceral response may not be the immediate outcome,” Sax said.

Adding to the growing conversation on IAS, Sax explained that it is important to look at the impacts of a species new to an area and realise that some impacts may benefit people and the ecosystem while others may provide costs. “I think it’s reasonable to ask if the costs outweigh the benefits or vice versa before deciding on whether you should invest money in trying to eradicate or fight back a particular species,” he said.

Finding tailored solutions

A recent study highlighted the astronomical costs of invasive species on the Indian economy, revealing that the country has lost more than $127 billion over the last six decades due to the phenomena. In response to the study, researchers and policymakers told Mongabay India there is a dire need for long-term research, dedicated institutions, and dynamic management practices to address IAS.

The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, or IPBES, also reported that anthropogenic activities have introduced more than 37,000 species to regions and biomes worldwide, and more than 3,500 of these are considered harmful IAS.

As the number of invasive species grows, contextual analysis can aid in devising tailored management responses, explained Hiremath. “In conversations on invasive species, there is a push to focus on the predominant ones, and I agree; they are important. But at the same time, we need to be aware of the other species and catch them before they become widespread. We know that many of them will get there,” she said.

Hiremath added that responding to invasion requires multiple approaches. With widespread species like Prosopis, Lantana (Lantana camara), water hyacinth (Pontederia crassipes), and alligator weed (Alternanthera philoxeroides), eradication becomes a mammoth task. “In such cases, we have to prioritise landscapes and control and contain the species based on larger conservation goals and impacts on communities,” said Hiremath.

Ravi further added that scale and temporality are critical considerations for invasive species. With Lantana and Prosopis, introduced during the colonial era, restoring pre-invasive states will require extraordinary resources and financial means.

“Several factors need to be weighed when you consider restoration as a strategy to combat invasion. Apart from being time and capital-intensive, it is also an ecologically complex process. Removing one invasive species can invite another, and replicating pre-invasion conditions, even with adequate resources, can be difficult. This does not mean that we abandon the efforts altogether but manage the problem through social justice concerns in addition to the environmental factors,” she said.

As vital as understanding the past of an invasive species is, researchers also warn of a future where landscapes and ecosystems will be vastly modified. Recent research revealed that anthropogenic interference is increasing the spread of non-native species by 1,000 times compared to native species.

“About 50 years from now, most communities and organisms on the planet will significantly differ from what we see today. As it increasingly becomes the norm, finding value and ways to conserve biodiversity will be the bigger question amidst these changes than asking if a species is native,” Sax added.

Utilisation vs adaptation

Several research studies have focused on analysing the metabolites of invasive plants to harness them for pharmacological applications based on their antimicrobial, antiviral, and antioxidant activities. Other uses have also been examined, such as purifying chemically contaminated soil or treating industrial wastewater.

However, scientists at the Kerala Forest Research Institute (KFRI) caution that these are still experimental ideas and require more research to translate the outcomes better.

“With Lantana, for example, people have assessed the metabolites from its leaves, flowers and roots. But, when it comes to management, you will be dealing with the crude extract of the whole plant. We need more detailed analysis to profile metabolites from the whole plant at various stages of growth. At the research level, mechanisation for such large-scale extraction and analysis involves costs,” said Jithu U Krishnan, a Junior Scientist at KFRI.

Senior Scientist M Amruth opined that plant-derived metabolites from invasives are possible in pest management. These metabolites serve as solid defence mechanisms, enabling the invasive species to thrive in new environments.

But, a cost-benefit analysis is essential here since some invasive species may be too aggressive to be repurposed fast enough to check their spread. He gives the example of Senna spectabilis, a tree species causing widespread invasion in Wayanad. “For species like S. spectabilis, where one mature tree can produce more than 7000 seedlings, more stringent management methods need to be prioritised over finding values,” he said.

Hiremath agrees that this is a slippery slope. “Utilisation of invasive species and local adaptations by people managing them are very different things. Unless you are well aware of the perverse consequences, and don’t lose sight of the overall goal of management, you could end up promoting a species based on its benefits,” warned Hiremath.

Adaptive management for restoration

There have been increasing instances in India where invasive plants, a plentiful and renewable resource, have caught the eye of entrepreneurs. Mongabay India recently reported on how water hyacinth is being used to create eco-friendly paper and baskets while providing a safer working environment for women in northern India. Over the last three decades, in the Malai Mahadeshwara Hills (MM Hills) in Karnataka, ATREE researchers have worked with the Indigenous communities to develop a project to convert Lantana into furniture.

Around 120 families benefit from this activity, explained Siddappa Setty R, a senior scientist at ATREE. “The indigenous communities here are greatly dependent on non-timber forest products, and furniture making has increased the average income of a person from INR 6000 to INR 35,000 per year,” he said. An offshoot of this initiative went a step further – creating life-size elephant sculptures using Lantana as a visual message for conservation worldwide.

“Previously, the artisans had to walk just about 2 km to obtain Lantana for furniture making. Now, they have to walk up to 6 km, showing a reduction in Lantana density. We are also seeing an increase in native plant diversity in MM Hills,” said Setty.

Interactions between people and IAS are dynamic and vary over time, as are stakeholder dependencies, location (rural vs. urban, for example), and stakeholder demographics.

Charlie Shackleton, professor of Environmental Science at Rhodes University in South Africa, in a 2019 review, said that invasion biology has been dominated by ecological studies, followed by economic ones to justify their removal. “While there have been some local-level successes, biological invasions are accelerating despite these many studies and subsequent policies and regulations. This is because humans are the primary drivers of biological invasions. Therefore, it stands to reason that the human dimensions need greater prominence if there is any hope or intention to keep them in check or even reverse some of them,” he said.

Banner image: A herder resting under P. juliflora with his livestock. Image by Ramya Ravi.

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Renuka Kulkarni Editorial Coordinator

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Health impactsIndigenous PeoplesPlantsIndia

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