Maintaining the quality of soil or “soil health” is essential for agriculture and food production. To do this, a monitoring system for soils must be adopted which will give information on undesirable trends and given sufficient time these maybe reversed through soil conservation, soil protection measures and sustainable land management.
Ideally, soil health assessments should be made using indicators of soil biodiversity (key species, functional groups), soil ecosystem parameters (water storage/movement, structural stability, soil fertility, organic matter) and specific functions (N cycling, C cycling, microbial biomass activity and others) which will lead to the establishment of target values and thresholds. Any indicator which is adopted must account for the multiple dimensions of soil functions, such as productivity and environmental well-being, the multiple physical, chemical and biological factors which control bio-geochemical processes, and their variation in intensity over time and space relevant to land users. Mechanisms are required to inform and engage land users and policy makers in soil health monitoring programmes and in turn, for implementing changes in soil management and to develop policies that better reflect the value of soil health.
The need for soil biodiversity monitoring was identified in a recommendation made by the FAO to the Conference of Parties for the Convention on Biological Diversity which resulted in the implementation of an International Initiative for the Conservation and Sustainable Use of Soil Biodiversity (COP 6 Decision VI/5). Monitoring soil biodiversity is useful in assessing soil health as degradation of soil from erosion or compaction, contamination and decrease of soil organic matter can lead to loss of biodiversity. Biodiversity, itself is affected by overexploitation of soil, changes of climatic and hydrological regime, changes in land-use and competition from invasive species.
Several soil biodiversity indicators can be used depending on resources but a minimum of three (see box, left) have been proposed. However, which ever indicator is used, it must be relevant to the specific policy or research questions which need to be answered providing that a standardised methodology is adopted, they are complementary to each other and the results be easy to interpret.
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