World’s Soil Resources

Prepared by P. Reich
Figure 4.3 Historical land use change 1000 – 2005. Source: Klein Goldewijk et al., 2011.
The net loss of natural land has been dominated by loss of tropical forests (3.3 million km 2 ), tropical
grasslands (6.8 million km 2 ) and temperate grasslands (5.5 million km 2 ). Quantification from satellite imagery
of global forest change over the period 2000-2012 shows that tropical deforestation remains the predominant
source of losses (Hansen et al., 2013). However, there has been a reduced rate of deforestation in some regions
over the last decade, most notably in Brazil. This is coupled with a rising rate of afforestation in some areas in
recent decades, notably in Europe and the United States, and more recently in China, Vietnam and India (FAO,
2013).
4.3 | Interactions between soils, land use and management
Many soils are subject to some degree of direct or indirect human disturbance. However, distinguishing
natural from direct and indirect human influence is not always straightforward (Smith, 2005). Nonetheless,
some human activities have clear direct impacts. These include land use change, land management, land
degradation, soil sealing, and mining. The intensity of land use also has a great impact on soils. Soils are also
subject to indirect impacts arising from human activity, such as acid deposition (for example, sulphur and
nitrogen) and heavy metal pollution. In this section, we report the state-of-the-art understanding and the
knowledge gaps concerning these impacts on soils.
4.3.1 | Land use change and soil degradation
Land cover change (Section 4.2), for example from forest or natural grassland to pasture or cropland,
removes biomass and disturbs soils. This in turn leads to loss of soil carbon and other nutrients and to changes
in soil properties and in soil biodiversity. Some land cover conversions – for example, afforestation after
abandonment of cropland – can result in increases of soil carbon and nutrients. Land use that does not result
in a change of cover, such as forest harvest and regrowth, or increasing grazing intensity, can nonetheless
result in degradation of soil properties.
Status of the World’s Soil Resources | Main Report Soils and Humans
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