Contents lists available at ScienceDirect Int J Appl Earth Obs Geoinformation journal homepage: www.elsevier.com/locate/jag Analysis of land degradation processes on a tiger bush plateau in South West Niger using MODIS and LANDSAT TM/ETM+ data Edoardo Fiorillo ⁎ , Fabio Maselli, Vieri Tarchiani, Patrizio Vignaroli Institute of Biometeorology – National Research Council (IBIMET-CNR), Via G. Caproni 8, 50145 Florence, Italy ARTICLE INFO Keywords: Land clearing Sahel Remote sensing Tiger bush Fuelwood consumption ABSTRACT Remote sensing digital image analysis has been applied to monitor land clearing and degradation processes on a plateau covered by tiger bush near Niamey in South West Niger, where signs of severe landscape degradation due to fuelwood supply have been observed in the last decades. A MODIS NDVI dataset (2000–2015) and five LANDSAT images (1986–2012) were used to identify spatial and temporal dynamics and to emphasize areas of greater degradation. The study indicates that the land clearing found by previous investigations in the second part of the 20 th century is still ongoing, with a decreasing trend of MODIS NDVI values recorded in the period 2000–2015. This trend appeared to be linked to an increase in bare soil areas that was demonstrated by analysis of LANDSAT SAVI images. The investigation also indicated that rates of degradation are stronger in more de- teriorated areas like those located nearer Niamey; degradation patterns also tend to increase from the inner areas to the edges of the plateau. These results attest to the urgency to develop effective environmental preservation policies and find alternative solutions for domestic energy supply. 1. Introduction The Sahel is a transition zone between the Sahara desert and the sub-humid tropics characterized by a semi-arid climate with a relatively short growing season and long dry season. The Sahelian belt has been identified as a “hot spot” of global environmental change and has been the focus of much scientific attention in recent decades spurred by the chronic vulnerability of its population to recurring drought and the threat of long-term land degradation. After a dry period with prolonged droughts in the 1970s and 1980s, many scientists flagged large areas of the Sahel as irreversibly degraded land (Lamprey, 1988; Ayoub, 1998; Dregne, 2002). Recent scientific results suggest that the decades of abnormally dry conditions in the Sahel, which caused an apparently irreversible degradation, have been reversed by positive anomalies in rainfall (Hermann et al., 2005; Ali and Lebel, 2009; Fensholt and Rasmussen, 2011; Brandt et al., 2015). Various remote sensing studies (Hickler et al., 2005; Olsson et al., 2005; Fensholt et al., 2012; Dardel et al., 2014a) observed a positive trend in vegetation greenness over the last decades that is known as the re-greening of the Sahel. Many authors agree on the importance of increased rainfall as the main driver in- crementing vegetation greenness (Seaquist et al., 2009; Huber et al., 2011; Anyamba et al., 2014). However, while this trend appears clear at regional scale, at a finer scale this vegetation evolution is not uniform throughout the Sahel (Rasmussen et al., 2014; Dardel et al., 2014b); greening and degradation are spatially heterogeneous and caused by a combination of both anthropogenic and climatic factors. Some of the most commonly cited causes of degradation comprise a climate-driven degradation of ecosystems (droughts) and land use changes, for in- stance changes in crop practices (over-exploitation of land, shortening of fallow duration), rangeland management (over-grazing), or extensive wood cutting (deforestation) (Dardel et al., 2014b). One of the areas in the Sahelian belt where decreasing vegetation production has been observed from both long-term ground data and satellite archives is South West Niger. The landform in this area is dominated by plateaus and gentle slopes (glacis and swales). In general, plateaus are covered by a characteristic natural vegetation cover, called tiger bush, while glacis are cultivated. Tiger bush is typified by reg- ularly alternating bare-soil stripes with dense linear thickets arranged perpendicularly to the slope. It occurs in Niger in an area about 250 km wide, extending from approximately 12°30′N to 15°N and covering one third of the Sahelian zone (White, 1970). These natural forests are of considerable economic interest since they are the main source of live- stock forage and domestic energy. In the last decades part of the ve- getation cover on the plateaus has been harvested for fuelwood pro- duction, especially in areas adjacent to densely populated centers like the Niger capital Niamey. According to the Institut National De La Statistique (2013) the population of Niamey increased from around 400,000 habitants in 1988 to around 1,000,000 in 2012 with an http://dx.doi.org/10.1016/j.jag.2017.05.010 Received 29 August 2016; Received in revised form 5 May 2017; Accepted 22 May 2017 ⁎ Corresponding author. E-mail address: e.fiorillo@ibimet.cnr.it (E. Fiorillo). Int J Appl Earth Obs Geoinformation 62 (2017) 56–68 0303-2434/ © 2017 Elsevier B.V. All rights reserved. MARK