Humans messed up planet and altered environment 'substantially' at least 3000 years ago, much earlier than believed

An international study challenges prevailing opinions and potential dates for the start of the Anthropocene, the period during which human activity became a dominant influence on climate change and the global environment.


                            Humans messed up planet and altered environment 'substantially' at least 3000 years ago, much earlier than believed

Topics such as climate change, deforestation, global warming, and greenhouse gas emissions dominate international conversations and it is assumed that these are modern phenomena. However, a large collaborative study by a team of archaeologists reveals that early humans across the entire globe were changing and impacting their environments as far back as 10,000 years ago. The analysis, say the researchers, shows Earth had already been substantially transformed by human activities as early as 3,000 years ago. 

According to the researchers, to understand the current climate crisis, it is vital to understand the history of humans altering their environments. The research - which assessed global land use from 10,000 to 170 years ago - shows that land use by early farmers, pastoralists and even hunter-gatherers were extensive enough to have created significant changes to the planet and the global land cover by 3,000 to 4,000 years ago. This is much earlier than has been previously recognized by scientists. 

The finding - that there was global environmental impact by land use at least 3,000 years ago - implies that the idea of seeing human impact on the environment as a newer phenomenon is too focused on the recent past, says the team. It challenges prevailing opinions and potential dates for the start of the Anthropocene - which refers to the period during which human activity became a dominant influence on climate change and the global environment. 

“The global archaeological assessment of ancient land use reveals that prehistoric human activity had already substantially transformed the ecology of Earth by 3,000 years ago, even before intensive farming and the domestication of plants and animals. The results suggest that early hunter-gatherers, farmers, and pastoralists have had a far greater effect on Earth’s landscapes - much earlier and more broadly than previously thought. From the advent of agriculture and domesticated animals to increased pressures on wild animals and plants, the “heavy hand” of human activity is often written in the landscapes,” say the researchers in their findings published in Science.

View of the La Costa 2 Archaeological site. The main circular structures are residences of the agropastoral Tafí Culture, from c. 2,500 years ago. (Maria Marta Sampietro Vattuone)

Research incorporates local expertise of 255 archaeologists

The study, led by Lucas Stephens while a doctoral student at the University of Pennsylvania and a postdoctoral researcher at the University of Maryland Baltimore County, is part of a larger project called ArchaeoGLOBE - a crowdsourcing effort - where online surveys are used to gather information from regional experts on how land use has changed over time in 146 different areas around the world. Land use can be anything from hunting and gathering to farming to grazing animals. 

The paper says that 255 respondents filled out over 700 regional questionnaires, which provided the information for the study. The ArchaeoGLOBE project analyzes human land use across the globe from roughly 10,000 years ago, the time of hunters and gatherers, to the year 1850, after the Industrial Revolution. 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. The new map synthesized from the archaeologists argues that the human imprint on our planet’s soil goes back much earlier than the nuclear age.
 
“Many people have realized for some time now that the study of long-term human-environment interactions must include archaeological knowledge, but our research and dataset really open the door to this sort of collaboration at global scale for the first time,” says Stephens, now a research analyst with the Environmental Law & Policy Center in Chicago and an affiliate at the Max Planck Institute.

The aggregate knowledge paints a surprisingly clear, globally coherent picture: it shows that shifting cultivation and pastoralism had affected over 40% of Earth’s land area by 4,000 years ago. It also reveals that continuous cultivation was common to widespread over most of the planet by 2,000 years ago, over 1,000 years earlier than indicated by today’s most widely referenced land-use study, the History Database of the Global Environment, known as HYDE.

Andrea Kay from the Max Planck Institute for the Science of Human History and The University of Queensland, explains that the long-term cumulative changes by early food producers are greater than many realize. “Even small-scale or shifting agriculture can cause global change when considered at large scales and over long time-periods,” she adds.

According to the findings, foraging - which is defined as hunting, gathering, and fishing - was common in most parts of the world 10,000 years ago, but was declining in more than half the world’s regions by 3,000 years ago. Again, pastoralism - the raising of livestock - had spread by 8,000 years ago, from some of its origin areas in Southwest Asia to arid environments like North Africa and Eurasia, where it was common by 4,000 years ago. The analysis shows that by 6,000 years ago, some form of agriculture was being practiced in nearly half of the world’s regions, and by 3,000 years ago, it was widespread. Further, say the researchers, farming is generally thought to “replace” hunting and gathering as a means of food production, but in some areas, agriculture occurred simultaneously with, or as a complement to, foraging.

“About 12,000 years ago, humans were mainly foraging, meaning they didn’t interact with their environments as intensively as farmers generally do. And now we see that 3,000 years ago, we have people doing really invasive farming in many parts of the globe,” says Gary Feinman, MacArthur Curator of Anthropology at the Field Museum and one of the study’s authors.

Deliberate and controlled burning of vegetation has been used for landscape management for millennia, here seen outside Kabwe, Zambia. (Andrea Kay)

The researchers say that humans in these time periods began clearing out forests to plant food and domesticating plants and animals to make them dependent on human interaction. Early herders also changed their surroundings through land clearance and selective breeding. While these changes were at varying paces, the examples are now known to be widespread and can provide insight into how people came to degrade their relationship with the Earth and its natural resources.

“This type of work causes us to rethink the role of humans in environmental systems, particularly in the way we understand ‘natural’ environments. 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,” says Lucas. 

The ArchaeoGLOBE maps contain more information about some regions of the world than others, reflective of where much archaeological attention has been directed, researchers point out. That is partly due to the expertise of the archaeologists who participated in the current study, as well as the availability of resources and support for study in various locations. While extensive data was available from the Western and Northern hemispheres, study authors say, less-investigated regions clearly warrant more research.

Findings will help understand current climate crisis

According to the researchers, understanding the history of human impact on the environment has implications for addressing climate change. Now that researchers know the beginnings of environmental impact, they can use this data to study what solutions ancient civilizations used to mitigate the adverse effects of deforestation, water scarcity, and more. 

Human transformation of slopes for rice farming, Ubud, Bali. (Andrea Kay)

 

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. 

“Understanding how humans interact with the environment over the long-term past is one of the best things we can do to help us understand how people will deal with this in the future,” says Michael Barton, co-author and a professor at Arizona State University’s School of Human Evolution and Social Change. 

Researchers can look for evidence of whether ancient peoples’ actions benefited or harmed biodiversity and allowed them to live sustainably or not in an area for a long amount of time. Studying their environmental successes and failures can give a better idea of how to create positive change as humans continue to reshape the planet.

The study also has implications for the Earth system models used to predict future human environmental impact. Accurate predictions rely on comparing the present to the past - and the data currently representing Earth’s past that is used for those models underestimates the human impact.

“It’s time to get beyond the most 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,” says co-author Erle Ellis of the University of Maryland Baltimore County, who initially proposed and helped design the study.

In a linked commentary, Professor Neil Roberts from the University of Plymouth says that impressive results of collaborative “big data” analyses by the ArchaeoGLOBE team indicate that human transformation of Earth’s land surface began well before the testing of the first atomic bomb, invention of the steam engine, or other proposed markers for the onset of the Anthropocene. “A recent report from the Intergovernmental Panel on Climate Change (IPCC) makes clear that better land management has a key role to play in keeping global warming to below 2°C. For this to occur, it is essential to take a long-term view on carbon release and the changing use of land. The ArchaeoGLOBE results should aid scientists in this endeavor,” he adds. 

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