Looking to the past to understand the impacts of human land use in South Asia

Whether through agricultural practices, deforestation, or urbanization, how modern humans use land has had an unprecedented impact on the planet. But historical information on human land use is lacking, impacting the quality of the climate models used today.

An international group of archaeologists, historians, geographers, paleoecologists, and modelers has been working to address this gap. They make up the Past Global Changes (PAGES) LandCover6K working group, which formed in 2014 to reconstruct human land use and land cover over the past 12,000 years.

In a new paper published in PLOS One, the group presented the first large-scale synthesis of archeological evidence showing how humans used land in South Asia at both 12,000 (early Holocene) and 6,000 (mid-Holocene) years ago. They found that hunter-gatherer-fisher-foraging remained the dominant land use across these periods, encompassing a variety of practices and approaches. They also saw shifts in forest utilization, more use of coastal resources, and the start of agriculture—though it was spread unevenly across the subcontinent—6,000 years ago.

Demonstrating the long history of how people adapted to the “diverse and complex landscapes and ecologies” in South Asia is “an important step for modeling the impacts of human populations and thinking about their footprints in a longue-durée [long duration] perspective,” the authors write.

This paper shows that there was less evidence about land use practices in South Asia 12,000 years ago than in earlier periods, which could be a function of how artifacts are classified or people not living in places they had lived earlier, says co-lead author Kathleen Morrison, the Sally and Alvin V. Shoemaker Professor of Anthropology at Penn’s School of Arts & Sciences. “More importantly, perhaps, we found that the extent of agriculture at 6,000 years ago was quite limited.”

She adds that while agriculture in South Asia appeared 9,000 years ago in what is now Pakistan, it remained limited in size and scope 3,000 years later, only appearing in small pockets across the continent.

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The first author on the study is Jennifer Bates, assistant professor of archaeological science at Seoul University who was a postdoctoral fellow in Morrison’s lab when work on the paper began. Other Penn-affiliated authors are Austin Chad Hill, an anthropology postdoc Morrison hired to work on LandCover6K because of his spatial analysis and archaeological skills, and Emily Hammer, assistant professor of digital humanities, archaeology, and anthropology of the ancient world in the Department of Middle Eastern Languages & Cultures.

The approach in the paper utilized archaeological and historical data, incorporating forms of evidence collectively known as landscape archaeology. For example, Morrison explains, bones provide information about domestic animals, plant remains shed light on farming, and evidence of canals and other forms of irrigation helps researchers understand land use.

The authors note that South Asia is “a critical location for understanding the long-term histories and consequences of human land use,” as it has a long history of human occupation and is currently home to more than one billion people.

“The South Asia data are just one piece of the global puzzle, from the LandCover6k point of view,” Morrison says, noting that the data will be used to help correct anthropogenic land cover change models and thus help improve the broader climate models using those models.

Eight years for analyzing thousands of years

The LandCover6K working group ended in 2021, but is still producing work related to its three project tracks: land cover, land use, and modeling. Group founder Marie-Jose Gaillard, a professor emeritus in botany-vegetation history and paleoecology at Linnaeus University in Sweden, leads the land cover aspect, which analyzes pollen records to understand past vegetation. Morrison leads the land use part and says climate modelers requested “time slices” from 12,000 and 6,000 years ago.

It took years for the group to figure out how to compare land use reconstructions on a global scale, and they published their findings in 2021 on a new classification system.

“There are really significant differences in the amount and type of evidence for different time periods, and especially for different regions,” Morrison says. For example, Bangladesh has very few radiocarbon dates, so researchers had to develop new ways of handling variations in data coverage and quality.

Looking ahead

Morrison is curious to understand how agriculture became the dominant form of land use. “This isn’t just an environmental issue; there were also many linked social and economic changes that helped shape later history,” Morrison says.

As part of a project studying the last 5,000 years of environmental history in the South Indian state of Karnataka, Morrison and others from Penn’s Department of Anthropology are collaborating with the Archaeological Survey of India (ASI) on fieldwork at the site of Brahmagiri, where scholars previously found evidence for the earliest agriculture in the region.

This project will involve studying plant and animal remains along with the vestiges of past villages, towns, and cities, she says. Additionally, the team is working to make training opportunities available for Indian scholars seeking to learn new analytical methods, and they are working on agreements between the Penn Museum and ASI.

“Although the results of this project will only fill a few grid squares in the larger LandCover6k project,” Morrison says, “our insights from this work, as well as future work by the students and scholars we’re helping train now, should add to our overall understanding of the interconnected histories of humans and the environment.”

Kathleen Morrison is the Sally and Alvin V. Shoemaker Professor of Anthropology in the School of Arts & Sciences and faculty lead of the Environmental Innovations Initiative at the University of Pennsylvania.

The other co-authors are Penn’s Emily Hammer and Austin Chad Hill; Jennifer Bates of Seoul National University; M. Madella, C. Lancelotti, and O. Parque of Universitat Pompeu Fabra; N.J. Whitehouse of University of Glasgow; T. Abro and G.M. Vessar of Shah Abdul Latif University; P. Ajithprasad of the Maharaja Sayajirao University of Baroda; K. Anupama of the French Institute of Pondicherry; A. Casile of the French Institute of Pondicherry; A. Chandio of the Aror University of Art, Architecture, Design and Heritage; S. Chatterjee of SRM University; K. Gangopadhyay of the University of Calcutta; S. Haricharan of the Indian Institute of Technology Bombay; M. Hazarika of Cotton University; R. Korisettar of the National Institute of Advanced Studies; A. Kumar and S. Pappu of the Sharma Centre for Heritage Education; C.A. Petrie of the University of Cambridge; R. Premathilake of the University of Kelaniya; V. Selvakumar of Tamil University; S. Sen of Jahangirnagar University; M. Spate of La Trobe University; M. Trivedi of Stanford University; and V. Vinayak of the University of Delhi.

This research was supported by the Past Global Changes (PAGES) project, Swiss Academy of Sciences and the Chinese Academy of Sciences, Samsung Electronics Co. Ltd. (A0426-20220120), European Research Council (ERC-2017-Stg-759800), International Union for Quaternary Research, and the Centre for Planetary Wellbeing of the Universitat Pompeu Fabra.