Hunter-gatherer societies and early farming were transforming Earth thousands of years ago, long before greenhouse gas emissions and other effects often attributed to the middle of the 20th century.
Earlier this year, scientists suggested that the Anthropoecene, a geologic epoch defined by ways humans have altered Earth, began in 1950.
But the very definition of human activity and its effects is subject to debate by scientists. Some have even suggested the Industrial Revolution as the beginning of significant human impact on the environment and planet.
But a new global study has pooled together evidence to show that humans significantly altered land, contributing to Earth's transformation, as long as 10,000 years ago. Farming especially impacted the land by 3,000 years ago. The study published Thursday in the journal Science.
More than 250 archaeologists across the globe analyzed land use from 10,000 years ago to after the Industrial Revolution in 1850. Using this data, they were able to create a map as part of the ArchaeoGLOBE project. The project uses online surveys to collect information from experts in 146 locations around the world on the shift of land usage over time.
The definition of land use can include everything from hunting and gathering activities to farming and allowing animals to graze.
Foraging, also called hunting and gathering, was once a common practice around the world. By 3,000 years ago, it was fading as pastoralism, or raising livestock, spread from Southwest Asia to Eurasia and North Africa around 4,000 years ago. Farming also spread between 3,000 and 6,000 years ago. But in some parts of the world, farming and foraging happened simultaneously to complement each other.
"About 12,000 years ago, humans were mainly foraging, meaning they didn't interact with their environments as intensively as farmers generally do," said Gary Feinman, one of the study authors and MacArthur Curator of Anthropology at the Field Museum in Chicago. "And now we see that 3,000 years ago, we have people doing really invasive farming in many parts of the globe."
In order to farm the land, forests were cleared for planting. Domesticating and herding animals also required land clearing. In the case of these activities, it wasn't the pace that changed the land, but the widespread activity, the researchers said.
"We saw an accelerated trajectory of environmental impact," said Ryan Williams, study co-author and associate curator and head of anthropology at the Field Museum. "While the rate at which the environment is currently changing is much more drastic, we see the effects that human impacts had on the Earth thousands of years ago."
Understanding the ways that more ancient civilizations changed the planet also allows researchers to search for any solutions that were also created to prevent water scarcity or the negative impact of clearing forests.
"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, study author at 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.
The crowd-sourced data allowed the researchers to assess and understand regions that haven't been studied as thoroughly in the past. The authors of the study hope that this is just the beginning of studying regions that have been closed off due to transportation issues, war, harsh environments or other factors.
"What really got me here was not so much the results, although I think that the results provide a foundation to support what many archeologists suspected," says Feinman. "But I think the most innovative aspect of this was the whole research design. To gather information from 250 scholars and to make sure that the whole world was covered, that's really something."
Changes to the climate and environment today happen at a quicker pace with more widespread effects. Research like this can lay the foundation for understanding how it happens and ways to mitigate the harmful changes.
"There's such a focus on how the present is different from the past in contemporary science. I think this study provides a check, a counter-weight to that, by showing that yes, there have been more accelerated changes in land use recently, but humans have been doing this for a long time. And the patterns start 3,000 years ago," says Feinman. "It shows that the problems we face today are very deep-rooted, and they are going to take more than simple solutions to solve. They cannot be ignored."