- Recording and monitoring bird calls to map soundscapes after a restoration project can help detect changes in the health of a forest.
- Scientists are stringing recorders around trees in eastern Madhya Pradesh to listen to bird calls and monitor changes in health of restored dry, deciduous forests after the removal of invasive shrub Lantana camara.
- Such soundscape measurements can create baseline data to keep track of longterm changes in forests. But bioacoustics need to be complemented with physical ground truthing surveys to draw effective conclusions on restoration outcomes.
“We are independent from Lantana’s fury,” beams Basant Jharia, a local community member in Central India, a region overwhelmed by the spread of the invasive Lantana plants.
Atop a mound that was once awash with Lantana thickets, he points to a tangled mass of upturned, dead Lantana bushes in a patch of land in Chicchari village in Mandla district in eastern Madhya Pradesh, home to significant stretches of dry, deciduous forests in India.
Jharia describes his and his community’s experience with Lantana in the 14-hectare common property land, saying that the invasive species, with its impenetrable bushes, deterred the community from accessing a small plot of land for their livelihood. Here, Lantana smothered the growth of native plants such as tendu and mahua, the produce of which is seasonally collected and sold. It is also used for daily needs (medicinal plants and grazing livestock).
Introduced in India as an ornamental plant in the early 1800s, Lantana escaped from gardens and spread across ecosystems, now occupying 40 percent of India’s tiger range alone including vast swathes in Central India. The people in the region call Lantana, “baramasiya”, which means ‘of 12 months’ in Hindi, because it remains green throughout the year. “We also used to guard our farms from crop-raiding wild animals because they hid in the Lantana bushes,” recalls Jharia.
The community then voluntarily began removing Lantana thickets in 2017. The effort was subsequently supported by the state forest department and the Foundation for Ecological Security. “Gradually, the forest came back… the medicinal plants grew back with the removal of Lantana and we continue to monitor the land for Lantana and remove it accordingly,” adds Jharia.
The revival of trees of local origin and importance following Lantana removal that brought back livelihood benefits of the ecosystem to the community also left its mark on the soundscape of the restored area, signalling the potential of these small-scale restoration efforts to contribute to ecological health, says restoration ecologist Pooja Choksi, a recent graduate of Columbia University, and co-founder of Project Dhvani, an acoustics research collaboration.
“A lot of the acoustics research that has taken place has largely been in humid forests. So overall, I would say dry deciduous forests were an underrepresented biome,” Choksi told Mongabay-India on their visit to the restored sites in Mandla.
Choksi and her colleagues used sound recorders to monitor changes in the soundscape after a restoration project in the eastern Madhya Pradesh landscape. The study was carried out in restored villages in the officially designated buffer of Kanha National Park in Bichhiya, a subdistrict of Mandla, which lies in a significant tiger landscape. The researchers eavesdropped on bird calls to understand restoration (through Lantana removal), including at Chicchari.
They tied acoustic recorders to tree trunks at vantage points in three sets of study sites – restored area, forest with naturally low densities of Lantana camara, and forest with high densities of the invasive shrub. Findings suggest that the soundscape was more active at the restoration site (more sounds from restored sites), “which is generally a positive sign for ecological health,” but could also be a temporary effect of the animals reorganising after the disruption of the L. camara removal.
Studying 55 sampling locations, over two years, Choksi and colleagues found that although there was no significant difference in the total number of bird species across all the sites, when they broke it down to generalist species (those that can live in different kinds of habitats from farm to forest) and forest specialists, there were a few differences.
“Unrestored sites had a significantly higher number of generalist species, which means that they don’t need specific forest trees to survive. In terms of a forest affiliate species, we didn’t find a significant difference, but we definitely found that restored sites had a higher number of forest affiliated species than unrestored sites,” says Choksi.
As India pushes to restore 26 million hectares of degraded and deforested land by 2030 under the Bonn Challenge, bioacoustics can effectively aid monitoring of long-term social and ecological impacts of such efforts, the researchers say. Physical surveys to document bird calls and insects over the same sampling period would help understand better the changes in the ecosystem in complement to measuring soundscapes.
“Given how slowly tropical dry forests regenerate, I think it will take a few more years to see changes in these forests, if any,” she says.
“Combining bioacoustics of birds with insects and mammals will provide fairly good key parameters to monitoring success of the restoration. A fully restored ecosystem should have biodiversity and function as before degradation,” restoration scientist C.R. Babu, professor emeritus at the Department of Environmental Studies, at Delhi University, told Mongabay-India. He was not associated with bioacoustics research.
“But how would you distinguish between a restored ecosystem and an ecosystem infested with Lantana that has attracted birds?” asks Babu.
The recently adopted Kunming-Montreal Global Biodiversity Framework (GBF), a global policy instrument to protect nature, recognised nature-based solutions, with biodiversity benefits underpinning successful nature-based solutions, such as ecological restoration.
People’s perception of biodiversity benefits
Choksi, in her research, wanted to focus on restored sites situated in forests used by the communities. “This is very much a landscape where people rely on forests,” she says, which is why their perceptions about what makes a healthy forest also matters. The reference sites she chose for the study were based on what people considered as a healthy forest.
“Most of the time, people said, ‘Thoda saaf hona chahiye, chal sakte hain’ (It should be clear and penetrable enough so that they can walk through the forest) and they would want certain species in the forest. It’s a seasonally dry forest, we tend to have slightly walkable forests, I like to call them walkable as compared to humid forests. So, most of the time, they meant that there was no Lantana in that forest.”
Dudhiya, a native medicinal species, also grows under the forest canopy like Lantana but its growth doesn’t obstruct people’s movement.
“So a lot of the places that people considered very healthy forest, which I used in my papers as reference sites, were also quite rich in their understory, but it was just not like Lantana, which is almost impenetrable.”
Jharia, who lives in Chicchari observes that children recently spotted the Indian roller bird (neelkanth) in the patch after Lantana removal.
“We really need to put perceptions in the centre of our conversations, because for a carnivore ecologist, Lantana has a lot of benefits for large cats; they leave their cubs in there. It’s great for hunting, there are benefits to different species, right. So maybe if you asked a carnivore ecologist, they would say that an unrestored site is fantastic,” said Choksi. “But maybe you ask a local community member who thinks that that’s hindering the growth of species they want, you will get a different answer.”
Farmer Prahlad in Magadha near the Dulhadhabrai forest, another restored site that is part of the study, illustrates a clear benefit to his community that he attributes to restoration (Lantana removal). He says the restoration has helped ward off wild animals such as nilgai, chital and wild boar, from raiding crops, a direct economic benefit. The Lantana bushes would camouflage the animals.
“If we farmed an area of two acres, we would lose one acre to crop raids,” he says.
For the last four years, one or two members of the 30 households in Magadha get together to weed out Lantana from August to October when the forest floor is still wet and the bush has not yet flowered. They are paid by the forest department.
“The forest was much denser earlier. It can become denser once the smaller understorey plants start sprouting as Lantana disappears. They are getting the space they need to grow. And earlier, wild animals would eat the fruits that would fall to the ground, inhibiting new plants,” adds Prahlad.
Choksi is also analysing vegetation for a closer look at forests that are left to come back on their own. The soundscape research has generated a baseline data that researchers hope can feed into crafting long term monitoring protocols with bioacoustics.
“Even though acoustics is limited in what it can tell us, I feel like we’re only getting better at connecting it to ground data, the same way satellite imagery has that connection… of connecting real forest data with what it appears like on a satellite image.”
“I feel like we’re kind of going through that same phase where we start connecting the real ground truthing data to this (soundscape) data,” adds Choksi.
Banner image: Greater racket-tailed drongo. Photo by Md shahanshah bappy/Wikimedia Commons.