Remote Sensing Identification of Threshold Zones along a Mediterranean to Arid Climatic Gradient

Debates regarding desertification have been heated especially since Thomas and Middleton (1994) challenged the marching desert myth in response to earlier suggestions by Lamprey (1975) that the Sahara desert boundary in Sudan is advancing by 5.5 km every year. Controversies in interpreting spatial and temporal information regarding shifts in desert threshold zones are not limited to the Sahel region (e.g., Nicholson 2011) but also characterize other semiarid regions (Veron et al. 2006) and the semiarid margins of the Mediterranean in particular (Safriel 2009; Thornes 2000). Although there is a consensus regarding the important role of remote sensing in monitoring desertification, there are disagreements regarding the interpretation of satellite imagery for this purpose. This is well exemplified by the disagreement of Hein and De Ridder (2006) with claims regarding greening of the Sahel made by Herrmann et al. (2005). According to Veron et al. (2006), controversies regarding desertification emerge mainly from methodological and terminological differences. They suggest that improvements in exploring desertification over large regions may be obtained by strengthening the synergy between ecology and remote sensing. Within such an approach, this remote sensing study implements vegetation phenomenologies in investigating ecosystems’ transition between semiarid Mediterranean to arid region. Three modes of vegetation change are analyzed: green vegetation cover (GVC) change between years of extreme high and low rainfall levels, life-forms’ composition change, and variations in spatial erosion versus recovery potentials. Landsat images of the climatic gradient between the Judean Mountains in central Israel and the Judean Desert in the east and the Negev Desert in the south (Figure 12.1) facilitate this eco-exploration.