Quaternary Science Reviews 28 (2009) 3016–3034 Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev The prehistoric and preindustrial deforestation of Europe Jed O. Kaplan a,b,*, Kristen M. Krumhardt a, Niklaus Zimmermann b a ARVE Group, Environmental Engineering Institute, Ecole Polytechnique Fe´de´rale de Lausanne, Station 2, 1015 Lausanne, Switzerland b Land Use Dynamics Unit, Swiss Federal Institute WSL, Zu¨rcherstrasse 111, 9031 Birmensdorf, Switzerland article info abstract Article history: Humans have transformed Europe’s landscapes since the establishment of the first agricultural societies Received 27 March 2009 in the mid-Holocene. The most important anthropogenic alteration of the natural environment was the Received in revised form clearing of forests to establish cropland and pasture, and the exploitation of forests for fuel wood and 24 September 2009 construction materials. While the archaeological and paleoecological record documents the time history Accepted 28 September 2009 of anthropogenic deforestation at numerous individual sites, to study the effect that prehistoric and preindustrial deforestation had on continental-scale carbon and water cycles we require spatially explicit maps of changing forest cover through time. Previous attempts to map preindustrial anthropogenic land use and land cover change addressed only the recent past, or relied on simplistic extrapolations of present day land use patterns to past conditions. In this study we created a very high resolution, annually resolved time series of anthropogenic deforestation in Europe over the past three millennia by 1) digi- tizing and synthesizing a database of population history for Europe and surrounding areas, 2) developing a model to simulate anthropogenic deforestation based on population density that handles technological progress, and 3) applying the database and model to a gridded dataset of land suitability for agriculture and pasture to simulate spatial and temporal trends in anthropogenic deforestation. Our model results provide reasonable estimations of deforestation in Europe when compared to historical accounts. We simulate extensive European deforestation at 1000 BC, implying that past attempts to quantify anthro- pogenic perturbation of the Holocene carbon cycle may have greatly underestimated early human impact on the climate system. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction 1995; Berglund, 2000; Vermoere et al., 2000; Cordova and Lehman, 2005; Gaillard, 2007). This long history of anthropogenic activity Since the establishment of the first agricultural societies in had important implications for environmental change, from Europe in the mid-Holocene (Price, 2000), humans have substan- regional hydrology to possibly global climate, and contains lessons tially altered the European landscape. The most evident and for our understanding of what constitutes environmental sustain- influential of these anthropogenic land cover and land use changes ability. In the current study, we attempt to estimate at high spatial (LCLUC) has probably been the clearance of forests and woodlands and temporal resolution, the patterns of anthropogenic deforesta- for cropland and pasture and as a source of fuel wood and tion in Europe from the time agriculture was firmly established construction materials (Darby, 1956; Hughes and Thirgood, 1982). across the entire continent until the Industrial Revolution. The rich paleoecological and archaeological record in Europe Though it is certain that the forests of many European countries provides ample evidence that many European regions experienced were substantially cleared before the Industrial Revolution (in intensive, continuous human occupation throughout the Holocene Europe, ca. 1790–1900), we lack a clear dataset describing the (e.g., Clark et al., 1989; Brewer et al., 2008; for a review see also progression of deforestation that occurred during prehistoric and Dearing, 2006). Indeed, some regions of Europe probably experi- preindustrial times. The first studies that attempted to map the enced successive cycles of deforestation, abandonment, and temporal pattern of anthropogenic land use and land cover change afforestation in the 6000 years of human history preceding the at the global to continental-scale before AD 1850 were limited in Industrial Revolution (e.g., Behre, 1988; Bintliff, 1993; Lagerås et al., temporal extent to AD 1700 and relied on simplistic relationships between 20th century patterns of land use to extrapolate to earlier times (Ramankutty and Foley, 1999; Klein Goldewijk, 2001). constructed a contemporary permanent croplands map as * Corresponding author. Tel.: þ41 21 693 8058; fax: þ41 21 693 3913. E-mail addresses: jed.kaplan@epfl.ch (J.O. Kaplan), kristen.krumhardt@epfl.ch a starting point for their model, and then ran a land cover change (K.M. Krumhardt), [email protected] (N. Zimmermann). model backwards in time to the year 1700 using any available 0277-3791/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2009.09.028 J.O. Kaplan et al. / Quaternary Science Reviews 28 (2009) 3016–3034 3017 historical cropland data as a constraint. This simple model used an anthropogenic LCLUC on global climate are currently the subject of algorithm for distributing cropland spatially over time, leaving a lively debate (Ruddiman, 2007). Using a top down approach, country boundaries and other relics in the database. a number of studies (Ruddiman et al., 2004; Vavrus et al., 2008) The HYDE database of global historical land use change (Klein demonstrated the sensitivity of global climate to Holocene trends Goldewijk, 2001) was developed using population estimates as in atmospheric CO2 and methane concentrations. As Ruddiman has a proxy for the extent of agriculture over the past 300 years, argued (Ruddiman, 2005), these greenhouse gases could have had including both cropland and pastureland. The starting point of this anthropogenic origins from deforestation resulting in CO2 emis- model was a spatially explicit global population map overlaid with sions, and the introduction of substantial populations of ruminant country boundaries. Historical population records for each country animals and development of rice agriculture, which increased were then used for temporal variation, while, using the assumption methane emissions to the atmosphere. On the other hand, bottom that high population density areas stay in the same place over time, up modeling studies that attempted to estimate prehistoric and spatial variation was provided by population distribution. Next, preindustrial anthropogenic CO2 emissions concluded that these modern estimates of total cropland and pastureland per country emissions would have been too small to have had a substantial were allocated back in time according to population density, with effect on global climate (DeFries et al., 1999; Olofsson and Hickler, areas of higher population density being the first to be converted to 2007; Pongratz et al., 2009), and rather attribute the observed cropland and pasture. trends in CO2 and methane concentrations to natural sources. Most recently, Pongratz et al. (2008) synthesized a dataset of However, given the limitations of these datasets described above, it global LCLUC for the historical period (AD 800 – Present) that is conceptually possible that they significantly underestimate includes crop, pasture and natural land cover fractions. In this study, anthropogenic emissions. Recently, a paleoecological data the authors referenced published maps of agricultural areas from synthesis by Nevle and Bird (2008) concluded that afforestation the two studies described above (Ramankutty and Foley,1999; Klein after the collapse of populations in Latin America following Euro- Goldewijk, 2001) as a starting point, then found the ratio of total land pean contact could have been significant enough to perturb the area used per capita for crop and pasture at AD 1700 for each country, global carbon cycle and climate system. and finally, using this ratio, scaled estimates of crop and pasture area In light of these confounding results and the limitations of by historical population estimates per country. This method is based current datasets, we attempt a new analysis of preindustrial and on two major assumptions: 1) per capita land use for crop and prehistoric anthropogenic LCLUC using updated datasets of pasture did not change prior to AD 1700, (though ranges provided in historical population trends, climate and soils, and a novel method this dataset explicitly include uncertainties in estimates of past for inferring the relationship between population and land use population and technological change), and 2) the spatial pattern of based on observational forest cover data. Our goal is to quantify crop and pasture areas was exactly the same throughout the uncertainties in both population size and the rate of technological historical period as it was at AD 1700, i.e., the amount of land under change and to estimate the sensitivity of our model to these driving cultivation in each gridcell at any given time is simply the AD 1700 variables. Our study focuses on Europe and neighboring regions value scaled by relative population change. In this way, the Pongratz because 1) this area has a record of human impact that covers the et al. (2008) method propagates all uncertainties associated with the entire Holocene, 2) detailed estimates of historical