Kathleen D. Morrison, Land Use Coordinator
Landcover6k is an international and interdisciplinary working group dedicated to reconstructing land cover and land use across the Holocene. The initial goal of this effort is to critically evaluate and improve models of anthropogenic land cover change now being employed by climate scientists. This work is urgently needed. Current climate models make little use of the vast repository of evidence about human history, despite an awareness that humans are one agent of global change. Vegetation is known to change in response to many factors, including human land use, but the complex and variable relationships between land use and land cover are still insufficiently understood. Differing assumptions about these relationships have led to significant differences between models of anthropogenic land cover change, a critical shortcoming with immediate scientific and policy implications for work on global climate. However, the development of more accurate and complete historical land use and land cover maps will also support and fuel research into a wide variety of fields and thus are of interest well beyond the community of climate scholars.
This collaboration includes two parallel tracks: (1) data-based land cover (vegetation, water, exposed rock, etc.) reconstructions; and (2) data-based land use (human uses of landscapes) estimations. The first will be derived from paleoecological data including pollen, phytoliths, and other proxy measures of past vegetation. Land use is inferred from archaeological and historical evidence, including texts, maps, images, settlements, artifacts, and paleoecological data such as plant and animal remains from archaeological contexts. Land use is complex and variable, not easily amenable to quantification and not simple to infer. For this reason, we will build maps on the basis of a hierarchical and globally-uniform classification of land use categories to be developed by this group. Both the classification and its applications will be subjected to open discussion and revision; we anticipate several stages of work and periods of open response by scholars with local and regional expertise. While classifications are intrinsically limiting, this effort is necessary in order to bring historical and archaeological evidence to bear on critical issues of global climate; if social scientists and humanists do not participate, less-informed assumptions about human land use history (and its implications for land cover) will be made and used, regardless of our qualms.
To the extent that land use and land cover reconstructions derive from independent data sets, not only will they be useful for constraining models of anthropogenic land cover change, but more fundamentally, will help us better understand the relationships between land use and land cover through time. The inclusion of the historical human disciplines makes the Landcover 6k effort unique in the world of large-scale international scientific collaborations. This important collaboration presents both a significant challenge – we must bring together and commensurate diverse modes of knowledge on a spatially and temporally ambitious scale – and also an unprecedented opportunity for the work of social scientists and humanists to be seriously considered in work addressing one of the most important global issues of our day.
Background to the problem
Adequate incorporation of land cover in global and regional climate models is still one of the major priorities in the climate modeling community. In particular, anthropogenic land cover change (ALCC) is still not successfully implemented in these models. As a result, climate models that try to take anthropogenic land cover into account, either to retrodict the past or predict the future are seriously hampered (Strandberg et al. 2014). The inability of climate models to cope with anthropogenic land cover is due to the fact that the dynamic vegetation models coupled to global climate models (GCMs) or regional climate models (RCMs) simulate climate-induced vegetation (i.e. ‘potential natural vegetation’) but cannot simulate anthropogenic vegetation. Thus, scenarios of past anthropogenic land cover change (Klein Goldewijk et al. 2011; Kaplan et al. 2009, as well as others), show large differences (Gaillard et al. 2010).
The degree and form of long-term and especially pre-industrial human impact on climate is still a matter of debate, and the effects of anthropogenic burning, deforestation, farming, and other land use practices on global climate via biogeochemical and biogeophysical processes in the past are not yet fully understood. Such understanding is critical, however, for planning solutions and improved descriptions of past anthropogenic land cover change at both regional and global scales are therefore urgently needed.
LandCover6k will address land-cover change across the globe, working to document and disentangle changes induced by climate and other ‘natural’ forces and by human land use practices. Archaeologists have argued that land cover changes due to anthropogenic land use are very old, dating to periods well before the start of agriculture. While the beginnings of agriculture are dated to ca. 6000 calendar years BP in Europe – a date that has attracted the attention of climate modelers – farming is significantly older in other parts of the world. Therefore, LandCover6k’s efforts are not restricted to the last 6000 cal. years, but will cover the last ca. 10000 cal. years or the whole of the Holocene. We will also focus on the forms and consequences of other historical transitions, such as industrialization, that have been of interest to the climate community and will, we expect, highlight other changes of importance that have not yet been adequately modeled.
LandCover6k is a working group of PAGES (Past Global Changes). Founded in 1991, PAGES is a core project of the International Geosphere-Biosphere Programme (IGBP) and is funded by the U.S. and Swiss National Science Foundations, and the National Oceanic and Atmospheric Administration (NOAA). With the help of a large and open community of scholars from across the globe, as well as coordinators for specific world regions, the land use and land cover groups aim to develop regional and global maps of (1) forms of land use and (2) vegetation cover for the last 10,000 years. LandCover 6k is coordinated by Marie-José Guillard, of the Linnaeus University, Sweden. Kathleen Morrison of the University of Chicago is co-coordinator for Asia and coordinator of group 6, which brings together the historical, archaeological, and geographic community. LandCover6k launched at a meeting in Paris, February 18-20, 2015. For updates and links, visit http://www.pages-igbp.org/workinggroups/landcover6k/intro.
- Gaillard M-J, Sugita S, Mazier F, Trondman A-K, Broström A, Hickler T, Kaplan JO, Kjellström E, Kokfelt U, Kunes P, Lemmen C, Miller P, Olofsson J, Poska A, Rundgren M, Smith B, Strandberg G, Fyfe R, Nielsen AB, Alenius T, Balakauskas L, Barnekow L, Birks HJB, Bjune A, Björkman L, Giesecke T, Hjelle K, Kalnina L, Kangur M, van der Knaap WO, Koff T, Lageras P, Latalowa M, Leydet M, Lechterbeck J, Lindbladh M, Odgaard B, Peglar S, Segerström U, von Stedingk H & Seppä H (2010) Holocene land-cover reconstructions for studies on land cover-climate feedbacks (2010) Climate of the Past 6: 483–499.
- Kaplan JO, Krumhardt KM & Zimmermann N (2009) The prehistoric and preindustrial deforestation of Europe, Quaternary Science Reviews 28(27-28): 3016-3034.
- Klein Goldewijk K, Beusen A, van Drecht G & de Vos M (2011) The HYDE 3.1 spatially explicit database of human-induced global land-use change over the past 12,000 years, Global Ecology and Biogeography 20: 73–86.
- Strandberg G, Kjellström E, Poska A, Wagner S, Gaillard M-J, Trondman A-K, Mauri A, Davis BAS, Kaplan JO, Birks HJB, Bjune AE, Fyfe R, Giesecke T, Kalnina L, Kangur M, van der Knaap WO, Kokfelt U, Kuneš P, Lata\l owa M, Marquer L, Mazier F, Nielsen AB, Smith B, Seppä H, and Sugita S (2014) Regional climate model simulations for Europe at 6 and 0.2 k BP: sensitivity to changes in anthropogenic deforestation, Climate of the Past 10: 661-680.