ABSTRACT
The 2012 yearbook of the United Nations Environmental Programme (UNEP 2012, v) identies the depletion of soil and the growing number of end-of-life nuclear power reactors as some of the most pressing environmental issues to be solved by humankind in the coming decades (Figure 3.1). While intuitively unrelated, the two issues are closely connected through the future role of biomass for energy production, contributing the so-called energy-food-water nexus for land (UNCCD 2012). Efforts to protect the atmosphere and mitigate global warming do already draw heavily on soil resources, for example, in Brazil or Southeast Asia, where sugarcane and palm oil production have been increased signicantly during the past 20 years. While the production of ethanol from sugarcane in Brazil aims at limiting soil loss, the pressure to clear forest to replace the land “lost” to biofuel production may harm the soils there (Lapola et al. 2010). In southeast Asia, clearing of tropical rain forests has more immediate effects not only on vegetation, but also on soils (Fargione et al. 2008). Making matters worse, the positive effect on greenhouse gas emissions achieved by growing these biofuels is questionable because of emissions generated, among others, from the loss of living biomass after land clearance and the subsequent depletion of the soil organic carbon (OC)
3.1 Soil: The Threatened Sphere .................................................................................................. 37 3.2 Soil Degradation and Soil Loss .............................................................................................. 38
3.2.1 Soil Degradation ......................................................................................................... 38 3.2.2 Visible Processes of Soil Loss .................................................................................... 39
3.2.2.1 Splash and Rainwash ................................................................................... 39 3.2.2.2 Rill and Gully Erosion .................................................................................40 3.2.2.3 Wind Erosion and Dust Pollution ................................................................40 3.2.2.4 Mass Wasting and Erosion by Tillage ......................................................... 41
3.2.3 Invisible Soil Loss: Salinization, Waterlogging, Nutrient Depletion, and the Loss of Soil Structure .................................................................................... 42 3.2.3.1 The Threat of Irrigation ............................................................................... 42 3.2.3.2 Loss of Soil Fertility .................................................................................... 43 3.2.3.3 Soil Loss by Urbanization and Industrialization ......................................... 45
3.3 Consequences of Soil Loss ..................................................................................................... 45 3.3.1 Soil Erosion versus Soil Formation ............................................................................ 45 3.3.2 The End of an Empire .................................................................................................46 3.3.3 Soil and Slavery in the Old South of the United States ..............................................46
