In the earliest text written in Marathi, a language of millions in western and central India, a 13th-century religious figure named Cakradhara points to an acacia tree as a symbol of the cycle of death and reincarnation.
It's unlikely he imagined he would help today's scientists understand the history of India's vast lands.
But scholars say that centuries-old literary works like this could help reveal the history of the great expanses of savannas and grasslands that cover nearly 10% of India and more than a third of the land on Earth.
That history suggests that tropical grasslands aren't the remains of former forests that they're sometimes made out to be, which is important for deciding where to focus tree planting efforts in the future, researchers say.
In a new study to be published Nov. 25 in the British Ecological Society journal People and Nature, scientists turned to historical accounts of plants in stories and songs set in western India to determine what vegetation once grew there.
"The take-home for me is how little things have changed," said study author Ashish Nerlekar of Michigan State University. "It's fascinating that something hundreds of years old could so closely match what is around today and contrast so much with what people romanticize the past landscape to be."
The researchers came up with the idea for the study over coffee while comparing notes about their respective fields.
Co-author Digvijay Patil, a PhD student in archeology in the Indian Institute of Science Education and Research in Pune, mentioned he sometimes came across references to peculiar plants while combing through Sanskrit and Marathi texts for his research on sacred sites in western India.
Nerlekar, a plant scientist, recognized them as real species of trees and shrubs that dot the region's savannas.
So the team started poring over folk songs, poems and myths written or performed in Marathi and dating as far back as the 13th century — very little of which exists in databases — to find references to wild plants and map their locations.
In the state of Maharashtra where the works were set, today some 37,485 square kilometers consist of open grassy expanses — an area two-thirds as big as Lake Michigan.
These areas are frequently misunderstood, said Nerlekar, a postdoctoral fellow in MSU's Ecology, Evolution, and Behavior Program.
In policy and in popular imagination, tropical savannas in India and elsewhere have long been cast as the remains of former forests that were reduced by humans to their present state, and thus maligned as " wastelands ."
Under this view, they're often earmarked for tree planting campaigns aimed at restoring forests to help absorb carbon dioxide and address the climate crisis.
But this and other studies paint a different picture of their past.
The researchers uncovered mentions of 44 species of wild plants, nearly two thirds of which are characteristic of savannas.
For example, in one passage of the epic poem "Adi Parva," dated to about the 16th century, cowherders are attracted to the "empty" and "thorny" landscape of the Nira River valley by its abundant grass.
Another account involving the death of a 15th-century poet-saint at a pilgrimage site called Pandharpur tells of a taraṭī tree — which scientists know as a sun-loving species called Capparis divaricata — that sprouts from her grave.
The researchers also found eight references to the thorny acacia tree that Cakradhara singled out, a feathery-leaved species with pale yellow bark and white flowers called Vachellia leucophloea.
"It's a pretty iconic tree in the region, and it was common at that time also," Nerlekar said.
This and other windows into the past suggest that the region's savannas stretch back at least 750 years, existing long before the deforestation that took place in India during British rule.
Previous lines of evidence suggest that many of the world's tropical savannas including those in India are even more ancient.
For example, the fossilized remains of pollen grains and grass-feeding hippos and other animals suggest that the plants that grew in the region tens of thousands of years ago were typical of savannas, not forests.
There are good reasons to preserve savannas and grasslands today, Nerlekar said.
In India alone, they are home to more than 200 plant species found nowhere else on Earth — many of which were only recently described by science, and remain at risk as land is converted to farms and other uses.
"A lot of savanna biodiversity is also sacred," which means they have cultural value in addition to ecological value, " Nerlekar said.
Savannas also act as carbon sinks, because they absorb carbon dioxide that would otherwise stay in the atmosphere and contribute to warming.
And in Asia, Africa, Australia, and South America, they provide fodder for hundreds of millions of cattle, sheep and other grazing livestock.
An estimated 20% of the global human population rely on savannas and grasslands for their livelihoods. The researchers say these benefits could be lost if efforts to mitigate climate change include planting trees in places where there was no forest to begin with.
"These centuries-old stories provide us a rare glimpse into the past, and that the past was a savanna past, not a forested past," Nerlekar said.
This research was supported by grants from Michigan State University and IISER Pune.
CITATION: "Utilizing traditional literature to triangulate the ecological history of a tropical savanna," Ashish N. Nerlekar and Digvijay Patil. People and Nature, Nov. 25. DOI: 10.1002/pan3.70201
