Desertification, Drought, and Surface Vegetation: An Example from the West African Sahel

Abstract

Many assumptions have been made about the nature and character of desertification in West Africa. This paper examines the history of this issue, reviews the current state of our knowledge concerning the meteorological aspects of desertification, and presents the results of a select group of analyses related to this question. The common notion of desertification is of an advancing "desert," a generally irreversible anthropogenic process. This process has been linked to increased surface albedo, increased dust generation, and reduced productivity of the land. This study demonstrates that there has been no progressive change of either the Saharan boundary or vegetation cover in the Sahel during the last 16 years, nor has there been a systematic reduction of "productivity" as assessed by the water-use efficiency of the vegetation cover. WTiile it also showed little change in surface albedo during the years analyzed, this study suggests that a change in albedo of up to 0.10% since the 1950s is conceivable.

Fifty years of landscape evolution in Southwestern Mauritania by means of aerial photos

“…At the contrary, most of these areas have been replaced by rice fields after the construction of two dams to optimize water resources management of the Senegal River. These areas may therefore show a good resilience of vegetation from space when the analysis is realized based on low resolution satellite data such as the Pathfinder series of NOAA-AVHRR (Anyamba and Tucker, 2005;Eklundh and Olsson, 2003;Nicholson et al, 1998;Prince et al, 1998) but do not represent the true evolution of the environment. In other words, man continues land degradation except when large enterprises well financed allow land improvement, but at the detriment to protected forests.…”

The recent Sahel drought is real

“…Hulme, 1992;Lamb and Peppler, 1992;Nicholson et al, 2000;L'Hôte et al, 2002), vegetation cover (Tucker et al, 1991), dust transport (Prospero and Lamb, 2003), and other agricultural and societal data (e.g. Nicholson et al 1998;Tarhule and Lamb 2003; and numerous reports in news media). Several possible causes or mechanisms, including local land-atmosphere interactions (e.g.…”

The role of Remote Sensing in land degradation assessments: opportunities and challenges

“…This complexity partly arises due to an ongoing discussion on the definition of what actually constitutes degradation and how it should be measured (Reynolds et al, 2011). There are many definitions of LD (Herrmann & Hutchinson, 2005;Nicholson, Tucker, & Ba, 1998). For example, the definition by UNCCD refers to LD as the "reduction or loss of the biological or economic productivity and complexity of rainfed cropland, irrigated cropland, or range, pasture, forest and woodlands resulting from land uses or from a process or combination of processes, including processes arising from human activities and habitation patterns" ( § 5, UNCCD, 1994) (Figure 1).…”