The historical ecology of Namibian rangelands: Vegetation change since 1876 in response to local and global drivers Richard F. Rohde a, ⁎, M. Timm Hoffman b a Centre of African Studies, University of Edinburgh, 4 Carlton Street, Edinburgh EH4 1NJ, UK b Plant Conservation Unit, Department of Botany, University of Cape Town, Private Bag Rondebosch, 7700, South Africa abstract article info Article history: Received 28 July 2011 Received in revised form 27 October 2011 Accepted 27 October 2011 Available online 20 December 2011 Keywords: Repeat photography Climate change Bush encroachment Colonial ecological revolution Savanna ecology Pastoralism The influence of both local and global drivers on long-term changes in the vegetation of Namibia's extensive rangelands was investigated. Fifty-two historical photographs of the Palgrave Expedition of 1876 were re- photographed and used to document changes over more than 130 years, in grass, shrub and tree cover within three major biomes along a 1200 km climatic gradient in central and southern Namibia. We showed that pat- terns of change are correlated with mean annual precipitation (MAP) and that below a threshold of around 250 mm, vegetation has remained remarkably stable regardless of land-use or tenure regime. Above this threshold, an increase in tree cover is linked to the rainfall gradient, the legacies of historical events in the late 19th century, subsequent transformations in land-use and increased atmospheric CO 2 . We discuss these findings in relation to pastoral and settler societies, paleo- and historical climatic trends and predictions of vegetation change under future global warming scenarios. We argue that changes in land-use associated with colonialism (decimation of megaherbivores and wildlife browsers; fire suppression, cattle ranching), as well as the effects of CO 2 fertilisation provide the most parsimonious explanations for vegetation change. We found no evidence that aridification, as projected under future climate change scenarios, has started in the region. This study provided empirical evidence and theoretical insights into the relative importance of local and global drivers of change in the savanna environments of central and southern Namibia and global savanna ecosystems more generally. © 2011 Elsevier B.V. All rights reserved. 1. Introduction This paper explores the historical ecology of central and southern Namibia using repeat landscape photography based on an extensive collection of archival images made in 1876. We present one of the most comprehensive accounts of what the region looked like and the causal factors that lay behind this, before the onset of coloniza- tion. Previous studies of long-term ecological responses to land-use and/or climate change in Namibia are either site specific(Ward et al., 2000; Heine, 2005), lack historical context (Eitel et al., 2002), or analyse environmental change at centennial, millennial or epochal temporal scales (Gil-Romera et al., 2007, 2010; Chase et al., 2009). Many sources of evidence suggest that landscapes of central and southern Namibia have changed radically since the 19th century but there are no detailed documentary sources that authenticate the state of the pre-colonial environment and how it has changed since then, across such a large spatial scale. Understanding the extent and cause of change is important since degradation in Namibia is commonly blamed on inappropriate land- use practices (local drivers) leading to bush encroachment, soil ero- sion, aridification and a decline in agrarian productivity (Eitel et al., 2002; de Klerk, 2004; Getzin, 2005; Dirkx et al., 2008). Furthermore, future climate change scenarios predict that these ecological process- es will be exacerbated by the regional impact of global drivers in the form of anthropogenic global warming (Midgley et al., 2005; Haensler et al., 2011). Future projections based on bioclimatic envelope models suggest that desert and arid shrublands will expand into present grassland savannas with a concomitant reduction in net primary pro- ductivity (Thuiller et al., 2006) and negative impacts on biodiversity, ecosystem services and livelihoods (Kruger, 1997; de Wit and Stankiewicz, 2006; Reid et al., 2007). Using the detailed evidence pro- vided by repeat photography spanning more than 130 years we were able to test claims about the causes of change in the past and identify trends in vegetation dynamics that relate to future climate change projections. We describe and analyse vegetation change across sever- al bioclimatic zones that co-occur with the steep west/east rainfall gradient from the Namib Desert to the interior highland savannas and from there south along a more gradual aridity gradient through the dwarf shrub savanna to the desert margin of the Orange River basin. We addressed the following key questions: (a) What are the major patterns of change in grass, shrub and tree cover since 1876 along an environmental gradient in Namibia? (b) How have political, Science of the Total Environment 416 (2012) 276–288 ⁎ Corresponding author. Tel.: + 44 131 332 4147. E-mail addresses: rick.rohde@ed.ac.uk (R.F. Rohde), Timm.Hoffman@uct.ac.za (M.T. Hoffman). 0048-9697/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2011.10.067 Contents lists available at SciVerse ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv