People transformed the world through land use by 3,000 years ago

 Humans started making an impact on the global ecosystem through intensive farming much earlier than previously estimated, according to a new study published in the journal Science.

Humans caused significant environmental change around the globe by about 3,000-4,000 years ago, much earlier than prior estimates, as revealed by a new international study

Max Planck Institute for the Science of Human History

IMAGE: Human transformation of slopes for rice farming, Ubud, Bali. view more 

Credit: Andrea Kay

Land use by early farmers, pastoralists and even hunter-gatherer societies was extensive enough to have created significant global landcover change by 3,000-4,000 years ago. This is much earlier than has been recognised, and challenges prevailing opinions concerning a mid-20th century start date for the Anthropocene. These are the findings of a new study published this week in Science, by a large international team of archaeologists and environmental scientists.
This study brought together several hundred archaeologists from around the world, who pooled extensive datasets summarising decades of archaeological research. Nicole Boivin, Director of the Department of Archaeology at the Max Planck Institute for the Science of Human History and a lead author on the study, notes that "archaeologists possess critical datasets for assessing long-term human impacts to the natural world, but these remain largely untapped in terms of global-scale assessments". She observes that "this novel crowd-sourcing approach to pooling archaeological data is extremely innovative, and has provided researchers with a unique perspective".
Unique collaboration allows for creation of large database of archaeological data to study past environmental change The ArchaeoGLOBE project was coordinated by an international team of researchers who developed an online survey to gather past land-use estimates from archaeologists with regional expertise. The current study offers a novel way to assess archaeological knowledge on human land use across the globe over the past 10,000 years. By incorporating online archaeological crowdsourcing, the study was able to incorporate the local expertise of 255 archaeologists to reach an unprecedented level of global coverage. This global archaeological assessment, and the collaborative approach it represents, will help stimulate and support future efforts towards the common goal of understanding early land use as a driver of long-term global environmental changes across the Earth system, including changes in climate.
"This type of work causes us to rethink the role of humans in environmental systems, particularly in the way we understand 'natural' environments," said Lucas Stephens of the University of Maryland Baltimore County, University of Pennsylvania and Max Planck Institute for the Science of Human History, who led the global collaboration of archaeologists that produced the study. "It also allows us to identify patterns in the distribution of our data and prioritize future collection areas to improve the reliability of global datasets."
Study of archaeological data reveals huge impact of humans over thousands of years "While modern rates and scales of anthropogenic global change are far greater than those of the deep past, the long-term cumulative changes wrought by early food producers are greater than many realize," said Andrea Kay of the Max Planck Institute for the Science of Human History and The University of Queensland, a lead author on the study. "Even small-scale or shifting agriculture can cause global change when considered at large scales and over long time-periods," she adds.
By acknowledging the deep time impact of humans on this planet and better understanding human-environment interactions over the long term, the researchers believe we can better plan for future climate scenarios and possibly find ways of mitigating negative impacts on soils, vegetation, and climate. "It's time to get beyond the mostly recent paradigm of the Anthropocene and recognize that the long-term changes of the deep past have transformed the ecology of this planet, and produced the social-ecological infrastructures - agricultural and urban - that made the contemporary global changes possible," said Erle Ellis of University of Maryland Baltimore County, a senior author who initially proposed and helped design the study. "These past changes produced the social-ecological infrastructures - agricultural and urban - that made the contemporary global changes possible."
Led by archeologist Lucas Stephens, a researcher affiliated with the Max Planck Institute for the Science of Human History, ArchaeoGLOBE used a crowdsourcing approach, inviting experts in ancient land use to contribute to a questionnaire on 146 regions (covering all continents except Antarctica) at ten historical time intervals to assess and integrate archaeological knowledge at a global scale. The result was a complete, though uneven, meta-analysis of global land use over time.
Significantly, the study also reveals that hunting and gathering was more varied and complex than originally thought, helping archeologists to recognize that foragers "may have initiated dramatic and sometimes irreversible environmental change." Intensive forms of agriculture reported around the world included activities like clearing land, creating fields that were fixed on the landscape, raising large herds of animals, and putting increasing amounts of effort into growing food.
SMU anthropologist and ArchaeoGLOBE team member K. Ann Horsburgh notes the rise in agriculture and livestock is primarily due to growing populations needing to be fed.
"Food production such as agriculture and pastoralism, when compared with foraging in the same environment, is linked to a faster population growth and can sustain higher population densities," said Horsburgh.
Horsburgh, Assistant Professor of Anthropology, and McCoy, Associate Professor of Anthropology, provided information on land use in Africa and the remote islands of the Pacific, respectively. McCoy also brought his expertise in geospatial technology to study how people in the past inhabited and shaped the world around them, while Horsburgh brought her knowledge of ancient DNA to retrace the spread of domesticated animals.
The map could provide new light on how the spread of farming and herding were linked to major migrations in human prehistory.
"This is first time that regional expertise on ancient land use has been synthesized on this scale," Horsburgh said. "That matters because we know that although the shift from foraging to farming tends to be a 'one-way' transition, it did not progress the same way around the world. The details of how it did progress has shaped everything from our diets to the languages we speak today."
Horsburgh went on to say, "What remains the topic of intense study is how much of the transition is food producers spreading and displacing foragers, and how much is it foragers adopting or marrying into food producing groups, or some other scenario. Most of this was done in the absence of written records, so it is up to anthropology to sort things out.
"The natural next step for this revised model of the spread of different types, and intensities, of land use is to compare them with human genetics and linguistics and integrate these findings into the big story of humanity," said Horsburgh.