ArchaeoGLOBE Project*. 2019 Science 365(6456):897–902.
Environmentally transformative human use of land accelerated with the emergence of agriculture, but the extent, trajectory, and implications of these early changes are not well understood. An empirical global assessment of land use from 10,000 years before the present (yr B.P.) to 1850 CE reveals a planet largely transformed by hunter-gatherers, farmers, and pastoralists by 3000 years ago, considerably earlier than the dates in the land-use reconstructions commonly used by Earth scientists. Synthesis of knowledge contributed by more than 250 archaeologists highlighted gaps in archaeological expertise and data quality, which peaked for 2000 yr B.P. and in traditionally studied and wealthier regions. Archaeological reconstruction of global land-use history illuminates the deep roots of Earth’s transformation and challenges the emerging Anthropocene paradigm that large-scale anthropogenic global environmental change is mostly a recent phenomenon.
As I have covered in several blog posts on this site (here, here, and here for example) archaeologists have for some time argued that the roots of the Anthropocene (or the paleoanthropocene, or the ancient Anthropocene) lay in the long-term histories of human-environmental interactions going back millennia. While it is undeniable that there has been a significant acceleration in the post-WWII era, the archaeological record attests to a number of interventions that have left indelible marks on land cover, biodiversity, and the earth surface generally. Knowledge of these transformations, and the traditions that underwrite them, are crucial to understanding the inseparability of humans from the planetary system, but to also avoiding pitfalls of speculative grand narratives that emphasize the inevitability of contemporary social and ecological crises associated with modern capitalism, or limit the possibilities of just futures based on assumptions of human nature.
Despite the innumerable published local or regional examples, it has been difficult to synthesize archaeological knowledge of land use strategies at a global scale. There are any number of issues at play, including the variable and often fragmentary nature of archaeological resources, differences in the intensity or scale of archaeological investigations (due to the accessibility of cultural resources and/or funding priorities, for example), and language barriers. In lieu of accurate historical reconstructions, global and historical maps have been developed using economic and population models (such as the History Database of the Global Environment, or HYDE) or estimating land cover through pollen reconstructions or other high-resolution proxies. While very useful as points of comparison, these datasets lack a grounding in archaeological observations.
This paper by the ArchaeoGLOBE Project, of which I am a co-author, addresses two important issues regarding the history of human transformation of the environment via land use practices. The first regards the timing, intensity, and nature of land use across the globe as documented archaeologically. The second relates to method: How can one synthesize and generalize the often disparate and fragmentary finds of archaeology and present that synthesis in a fashion that is usable by other disciplines, or even by policy makers?
From a methods perspective, this project and the resulting Science paper represents what I think is an important shift towards crowd-sourcing expert archaeological knowledge. The core authors of the project developed a survey that was disseminated widely to professional archaeologists (although in the end there was still an anglophone bias in respondents). The survey split the globe into 146 regions. Experts like myself were asked to answer a series of questions about the state of archaeological knowledge in a region, such as the number of reports and the coverage of archaeological studies. Experts were also asked to identify the amount of land subject to different land use strategies (hunting and gathering, pastoralism, extensive agriculture, intensive agriculture, and urbanism) during 10 time intervals between 10,000 years ago and the year 2000. Those archaeologists who contributed knowledge on multiple regions were given the opportunity to continue as co-authors. Core authors worked to collate and analyze the data, generating a time series of land use maps (see above) and a number of insights about the global history of land use in addition to archaeological knowledge and practice. Significantly, all the data generated in 711 surveys from 255 archaeologists, along with the R code for the analyses, is publicly available online with a CC0 Public Domain license: https://dataverse.harvard.edu/dataverse/ArchaeoGLOBE.
One of the most powerful results of the project was the production of a series of maps showing (like that above) changes in land use over time (all the animations are available in the ArchaeoGLOBE repository). Indeed, these data show just how clearly complex the histories of land use transformations have been. At the scale of the globe, hunter-gatherers were widely engaged in land use by at least 10,000 years ago. As noted by the authors hunting and gathering is a problematic term at best, but could involve such practices as land clearing, burning, transplantation, and fisheries manipulation. So, too, the data suggest that between 6000 and 3000 years ago many (but importantly not all) regions saw the rise of extensive and intensive agriculture. Particularly in Europe, Southwest, and East Asia, and Northern Africa there was a concomitant decline in foraging. What is exciting, however, is that the data also highlight how often different strategies ran “in parallel” for millennia, such as hunting and gathering alongside extensive agriculture, or pastoralism and intensive agriculture. While at the scale of the globe intensive agriculture’s appearance may seem unilinear in nature, local histories still attest to complex interactions between communities with different strategies.
Having an accurate assessment of long-term global land use is critical for a number of reasons. Certainly, the details emerging from this study show that humans have been deeply involved in practices that have had ecosystem impacts for a long time. So, too, the results highlight the interconnections, and likely complementarity, of different land use strategies co-existing for long stretches of time. From an archaeological perspective, the results focus on regions that remain poorly documented (at least in the anglophone academic realm). Future work, for example, could identify alternative or novel strategies in these areas. By generating digestible time-series maps of land use change, the cumulative knowledge of archaeologists can make manifest human agencies in the world. These same maps can now be used as source material for other modeling studies, or to identify areas for collaborations to fill in real or apparent knowledge gaps.
A last point about the importance of these global land use histories regards narrative. From my perspective (just to be clear, I’m not speaking for other co-authors here), the maps and other resources generated by this project are a starting point, and equally should not be treated as inherently explanatory. While it is now evident that humans were actively transforming the globe in ways that are archaeologically measurable, there is nothing in the datasets themselves that provide necessary explanations for the apparent patterns. While one might be tempted to view the eventual dominance of intensive agriculture (and precipitous decline of hunting and gathering particularly after 1500 CE) as a natural consequence of human-environmental interactions, I would note that this is precisely the moment that European colonialism began to impact indigenous communities across the globe (see image (B) above). It was often in these contexts that “Old World” domesticates, as well as land use and tenure practices, were installed by colonizers intentionally at the expense of local communities and their land use traditions. These were inherently violent acts. Moving forward, we (as Anthropocene researchers) would be wise to acknowledge the possibilities of diverse land use (multiple overlapping strategies, for example), as well as these traumatic histories, and to imagine futures that promote alternative strategies over reproduced colonial impositions.