Abstract
In the 12,000 years preceding the Industrial Revolution, human activities led to significant changes in land cover, plant and animal distributions, surface hydrology, and biochemical cycles. Earth system models suggest that this anthropogenic land cover change influenced regional and global climate. However, the representation of past land use in earth system models is currently oversimplified. As a result, there are large uncertainties in the current understanding of the past and current state of the earth system. In order to improve representation of the variety and scale of impacts that past land use had on the earth system, a global effort is underway to aggregate and synthesize archaeological and historical evidence of land use systems. Here we present a simple, hierarchical classification of land use systems designed to be used with archaeological and historical data at a global scale and a schema of codes that identify land use practices common to a range of systems, both implemented in a geospatial database. The classification scheme and database resulted from an extensive process of consultation with researchers worldwide. Our scheme is designed to deliver consistent, empirically robust data for the improvement of land use models, while simultaneously allowing for a comparative, detailed mapping of land use relevant to the needs of historical scholars. To illustrate the benefits of the classification scheme and methods for mapping historical land use, we apply it to Mesopotamia and Arabia at 6 kya (c. 4000 BCE). The scheme will be used to describe land use by the Past Global Changes (PAGES) LandCover6k working group, an international project comprised of archaeologists, historians, geographers, paleoecologists, and modelers. Beyond this, the scheme has a wide utility for creating a common language between research and policy communities, linking archaeologists with climate modelers, biodiversity conservation workers and initiatives.
Highlights
Earth systems models, land cover, and the past earth system models are often seen as tools for exploring the future, they rely in part on understandings of the past, including models of land cover change through time
There is a critical need for data-based global assessments of past human land use
We know that regional-scale transformations in vegetation and even landforms were sometimes very dramatic, it is not yet clear how significant the aggregate of the many local records of landscape transformation documented by archaeologists, paleoecologists, and historians might be on a global scale
Summary
Earth system models are often seen as tools for exploring the future, they rely in part on understandings of the past, including models of land cover change through time. In order to explain how paleoenvironmental and archaeological data can improve earth system models, it is necessary to review these models and the limitations of their approach to land cover. Land cover influences climate through interactions between land and atmosphere. Land-atmosphere interactions currently constitute an area of uncertainty in climate projections, and it is a priority in the scientific community to improve earth system models by incorporating land cover change into simulations
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