- Some 3,000 years ago, our human ancestors were already substantially transforming Earth’s surface by farming and grazing livestock, according to a new study that crowdsourced the expert knowledge of more than 250 archaeologists from the around the world.
- This massive collaboration, termed the ArchaeGLOBE project, has helped build the first ever global picture of how human activities were altering the planet’s surface from 10,000 years ago right up to 1850.
- These estimates of the spread of agriculture and pastoralism suggest that humans were significantly transforming the planet earlier than what some recent studies and databases show, the researchers say.
- The ArchaeoGLOBE project dataset, however, has several data gaps and presents only part of our planet’s history.
Look around, and you’ll see examples of how we’ve modified our planet’s land surface: roads, buildings, farms, plantations. But is the widespread human impact on Earth a modern occurrence? No, according to a new study published in Science.
Some 3,000 years ago, our ancestors were already stripping away forests and substantially transforming Earth’s surface through farming and grazing livestock, researchers have found by crowdsourcing the expert knowledge of more than 250 archaeologists from the around the world.
Archaeologists typically focus on a particular region and time period. But this massive collaboration, termed the ArchaeGLOBE project, has helped build the first ever global picture of how human activities were altering the planet’s surface from 10,000 years ago, long before there were written records to keep track of the same, right up to 1850, or after the industrial revolution.
“Our open access dataset provides the first globally consistent dataset on land use over the past 10,000 years that is based on the expert knowledge of archaeologists,” Erle Ellis, a co-author of the study and professor at the University of Maryland, Baltimore County, told Mongabay. “It describes both the global patterns of this knowledge over time, and the timing of the emergence of agriculture, pastoralism and urbanism, and the decline of hunter-gatherer land use.”
To piece together humankind’s history of land use, the researchers divided Earth’s surface into 146 analytical regions spanning all continents except Antarctica. Then they sent out questionnaires to more than 1,300 archaeologists, asking them to contribute their understanding of how ancient peoples used the land in those regions at 10 different time points between 10,000 years ago up to 1850.
They received responses from 255 of the archaeologists, whose local knowledge helped the researchers map some broad global historical patterns.
Ten thousand years ago, for example, foragers and hunter-gatherers were widespread, while agriculture and pastoralism, or the practice of raising livestock, had been established in just a few regions around Southwest Asia and the Mediterranean.
By 8,000 years ago, pastoralism had spread out to arid areas such as North Africa and Eurasia, and by 4,000 years ago it had become common and widespread across the planet. Some form of agriculture, too, had spread to nearly half of the studied regions and become widespread by 3,000 years ago. Over that same period, foraging, hunting and gathering declined.
“One of the key questions remaining is to what degree hunter-gatherers modified landscapes around the world through burning, propagation of favored species, and other niche-constructing practices,” Ellis said. “Though our work confirms that hunter-gatherer use of land was widespread in most of the world by 10,000 years ago, the degree of their landscape modification and its local and global consequences demands further study.”
These estimates of the spread of agriculture and pastoralism suggest that humans were significantly transforming the planet earlier than what some recent studies and data show, the researchers say. This includes the History Database of the Global Environment (HYDE) model, a popular database of past land-use change that scientists frequently use to predict future environmental changes.
“We weren’t entirely surprised by the main findings because archaeologists have long been critical of the existing historical reconstructions of global land use based on models,” Ellis said. “However, we were impressed by the fact that archaeological experts confirmed that intensive agriculture emerged earlier, by centuries to thousands of years in many regions, than in the land use history model most used by Earth scientists.”
K. Anupama, a researcher at the Laboratory of Palynology & Paleoecology, French Institute of Pondicherry, India, also said the results weren’t unexpected.
“Traditionally, Earth and Ecological Sciences have been developed with a very clear distinction of ‘nature’ and ‘natural systems’ as something apart from all things ‘human’ or ‘human-made and/or human impacted,’” Anupama, who was not involved in the study, said in an email. “For long, this has been reflected in the assumptions underlying climate and earth system models too.
“Archeologists, historians and the humanities in general have known better — even if their studies are bracketed as ‘qualitative,’” she added. “This paper, though the methodology is not robust, can be commended especially for its efforts to build transdisciplinary bridges that could eventually help obtain the ‘quantitative’ land use data that is key to modeling efforts that use past data to help predict futures in our planet Earth.”
The ArchaeoGLOBE project dataset presents only part of our planet’s story. There are geographical gaps in archaeological evidence, for example. Many areas in Africa, Southeast Asia and South America, in particular, have not been studied much with regard to ancient land use.
“Many interrelated factors are responsible for the history of research in these areas, including resources and training available to archaeologists who study these areas, and the legacy of archaeological focus on ‘big monumental’ sites that draw tourists,” Lucas Stephens, who led the study while he was a doctoral student at the University of Pennsylvania and a postdoctoral researcher at the University of Maryland, Baltimore County, told Mongabay.
It was also a challenge to connect with archaeologists outside the English-speaking world, Ellis said.
“There were also regions where archaeologists had different assessments on land use histories, making consensus more difficult,” he added. “Nevertheless, we were delighted overall by the very positive responses of the more than 250 archaeologists that spent the time to contribute to our project.”
Evidence of past land use is hard to come by, especially at the global scale. So, despite the data gaps and biases, the ArchaeoGLOBE project presents the “first approximation of the global history of land use,” Stephens said.
“The IPCC [Intergovernmental Panel on Climate Change] just recently released its report on land use, food production, and climate change, reinforcing the idea that these are critical issues for the future of the Earth,” Stephens added. “But there is also a deep history of anthropogenic changes to the planet that has yet to be meaningfully incorporated in these discussions. That needs to change, and the ArchaeoGLOBE Project is a big step forward in doing so.”
Banner image of Val de Navarrés, País Valenciano, Spain, by Michael Barton.
Citation:
Stephens, L., Fuller, D., Boivin, N., Rick, T., Gauthier, N., Kay, A., … Ellis, E. (2019). Archaeological assessment reveals Earth’s early transformation through land use. Science, 365(6456), 897-902. doi:10.1126/science.aax1192