World’s Soil Resources

phenomena such as the onset of massive dust storms. Dust storms can arise either from destabilization of
vulnerable surface soils (the Dust Bowl), or from the drying of lake beds, or from desertification and loss of
vegetation and similar soil destabilizing activities over large scales. The rates of wind erosion associated with
sand storms may exceed 100 mm topsoil yr -1 in sensitive regions in the Sahel. Prolonged exposure is known to
pose respiratory health hazards to human population.
7.7.4 | Soil and flood hazard
Agricultural intensification has been linked to alteration of runoff mechanisms and to increased risk and
burden of floods (Marshall et al., 2014). Some of the primary changes in land management documented in
the United Kingdom and elsewhere that affect soils include: heavy traffic contributing to soil compaction,
tillage operation and consequent loss of soil structure, the formation of larger fields, choice of cover crops in
rainy seasons, and increased livestock densities (O’Connell et al., 2007). However, establishing rigorous causal
links between changes in land management practices, local runoff generation and catchment scale flood
behaviour remains a challenge (Ewen et al., 2013). Nevertheless, mounting evidence suggests that soil and
land management contribution to flood risk is not limited to management of lowland agricultural regions.
Management of upland soils and related impacts on runoff generation mechanisms cascade and also have
impacts on flood risk downstream (Wheater and Evans, 2009; Marshall et al., 2009). A recent review by Hall et
al. (2014) on flood trends in Europe (including climatic effects) confirms the important role of land use changes
(urbanization, afforestation, etc.) as key factors in modifying large scale flood risk. Some of the strategies for
reducing flood risk include afforestation in upland catchments (Ewen et al., 2013), creation of retention basins,
and adding floodplains by lowering levees (Hall et al., 2014).
7.7.5 | Hazards induced by thawing of permafrost soil
Permafrost is perennially frozen soil remaining at or below 0°C for at least two consecutive years (Brown et
al., 1998). Permafrost regions occupy about 24 percent of the exposed land area in the Northern Hemisphere
and in some high mountainous regions (UNEP, 2012). Expected thawing of permafrost is projected to induce
alterations in soil hydrology and biological activity, and to have an impact on the global carbon cycle (Schuur
et al., 2008). In addition, the thawing of permafrost is expected to change vegetation species and reshape
many ecosystem functions. The mechanical weakening of the previously frozen soil is likely to result in
foundation settling, with damage to buildings, roads, pipelines, railways and power lines (Nelson, Anisimov
and Shiklomonov, 2001; Jorgenson, Shur and Pullman, 2006). Estimates of infrastructure repair in Alaska up
to 2030 are in the range of US$ 6 billion (UNEP, 2012). Changes in mean temperature and snow cover also
affect sensitive permafrost in high mountains, and contribute to a higher risk of landslides and avalanches
(Gruber and Haeberli, 2007; Harris et al., 2009). Schoeneich et al. (2011) present an extensive report and case
studies, largely from the European Alps, on various slope movement hazards (landslides, rock fall, and debris
flow initiation) associated with degrading permafrost. Evidence suggests accelerated erosion rates of the
thawed permafrost, especially along coastlines and rivers banks as documented by Schreiner, Bianchi and
Rosenheim (2014) and Vonk et al. (2012), with subsequent transport of the carbon-rich sediment through river
systems to the ocean.
7.8 | Soil biota regulation
Soil biodiversity is vulnerable to many anthropogenic disturbances, including land use and climate change,
nitrogen enrichment, soil pollution, invasive species and the sealing of soil. A recent sensitivity analysis
revealed that increasing land use intensity and associated soil organic matter loss are placing the greatest
pressure on soil biodiversity (Gardi, Jeffery and Saltelli, 2013). Numerous studies report soil biodiversity declines
as result of the conversion of natural lands to agriculture (Bloemers et al., 1997; Eggleton et al., 2002; Dlamini
Status of the World’s Soil Resources | Main Report The impact of soil change on ecosystem services
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