Spatial Assessment of Land Degradation Risk for the Okavango River Catchment, Southern Africa

Abstract

The Okavango catchment in southern Africa is subject to environmental as well as socio‐economic transformation processes such as population growth and climate change. The degradation of soil and vegetation by deforestation and overgrazing is one of the downsides of this development, reducing the capacity of the land to provide ecosystem functions and services. In this study, climate simulations are brought together with secondary socioeconomic, pedologic and remote‐sensing data in a GIS‐based assessment of the factors commonly associated with land degradation risk. A high resolution overview is provided for decision‐makers and stakeholders in the region by identifying priority intervention areas where a long‐term decline in ecosystem function and land productivity is most likely to occur. The approach combines 19 risk factors into seven individual ratings for topography, landcover, soil, demography, infrastructure, livestock pressure and climate. These ratings are then weighted and combined into an integrated degradation risk index (DRI). The results show that the land degradation risk is quite heterogeneously distributed in the study area and caused by different factors. Three hot‐spots are identified and compared, one of which is in the far northwestern part of the catchment, one around the local center Rundu and one on the outskirts of the Okavango Delta. We conclude that the approach is suitable to give an overview on degradation risk in the study area, although the classification process is a crucial procedure that should be standardized for further research. Copyright © 2015 John Wiley & Sons, Ltd.

Historical Trajectory in Vegetation Cover in Northeastern Namibia Based on AVHRR Satellite Imagery (1982–2015)

“…This is especially the case in dryland ecosystems, where any slight change in land cover can easily lead to significant land degradation [3,4]. Land degradation has been defined as the "reduction in the capacity of the land to provide ecosystem goods and services and assure its functions over a period of time for the beneficiaries of these" [5] (p.1). Land degradation usually occurs due to long-term reduction in temporal and spatial vegetation cover and primary productivity [6].…”

“…Land degradation is categorized as vegetation degradation, soil degradation, and unsustainable water use practices [3]. Broadly speaking, land degradation is caused by the complex interaction of natural factors (e.g., droughts) and unsustainable anthropogenic land use practices (e.g., overexploitation of natural vegetation cover [5][6][7]. Globally, human-induced land degradation has negatively affected the well-being of at least 3.2 billion people [2].…”

Wind erosion reduction by water diversion in the lower Heihe River Basin, Northwest China

“…For example, water bodies can protect soil from wind erosion by completely covering the soil surface (Borrelli et al, ; Yan, Zhan, Liu, & Yuan, ), whereas vegetation cover on the soil surface can reduce wind erosion by decreasing the wind speed close to the ground (Borrelli et al, ; Wolfe & Nickling, ). Additionally, land degradation generally begins with the removal of natural vegetation, which is often exacerbated by human activities, one of the most important factors contributing to land degradation by wind erosion in arid regions (Guo et al, ; Weinzierl, Wehberg, Böhner, & Conrad, ). For example, the lower reaches of Heihe River Basin in Northwest China have suffered from serious land degradation by wind erosion, induced by both human and natural factors (Cheng et al, ).…”

“…There is an urgent need to identify land degradation hotspots, which can be met using GIS‐based wind erosion prediction models and remote sensing data (Weinzierl et al, ). On the one hand, remote sensing data such as the normalized difference vegetation index (NDVI) can provide deep insights in the past and present states of land degradation (Weinzierl et al, ).…”

Effect of soil coarseness on soil base cations and available micronutrients in a semi-arid sandy grassland

“…Together with reduction of plant cover, increased soil coarseness contributes to a loss of agricultural productivity, environmental deterioration, and associated social and economic disruptions (Vieira et al, 2015;Xie et al, 2015). In this case, it is urgent to combat desertification and study the causes, processes, consequences, and mechanisms of soil coarseness (Xu et al, 2012;Weinzierl et al, 2016).…”