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Global demand for food is increasing in terms of the quantity, quality and reliability of supplies. Currently, over 90 % of our food is grown on (or in) a virtually irreplaceable, non-renewable natural resource – the soil. This paper examines the latest research on selected soil degradation processes (soil erosion by water, compaction, loss of organic matter, loss of soil biodiversity and soil contamination) and specifically how they impact on food production. Every year, an estimated 12 million hectares of agricultural land are lost to soil degradation, adding to the billions of hectares that are already degraded. It is estimated that soil degradation leads to a potential loss of 20 million tonnes of grain per annum, but this is likely to be an underestimate, because the evidence base is limited in identifying direct impacts of soil degradation on food production. Some soil management practices have been used to mask the effects of soil degradation on food production (e.g., additions of chemical fertilisers), but comprehensive soil conservation practices are required to respond to the multiple problems of soil degradation if the world is to be able to feed more than 9 billion people by 2050.

Numerous scientific challenges arise when designing a soil monitoring network (SMN), especially when assessing large areas and several properties that are driven by numerous controlling factors of various origins and scales. Different broad approaches to the establishment of SMNs are distinguished. It is essential to establish an adequate sampling protocol that can be applied rigorously at each sampling location and time. We make recommendations regarding the within-site sampling of soil. Different statistical methods should be associated with the different types of sampling design. We review new statistical methods that account for different sources of uncertainty. Except for those parameters for which a consensus exists, the question of testing method harmonisation remains a very difficult issue. The establishment of benchmark sites devoted to harmonisation and inter-calibration is advocated as a technical solution. However, to our present knowledge, no study has addressed crucial scientific issues such as how many calibration sites are necessary and how to locate them.