Why should soil biodiversity by conserved and managed ?

There are agronomic, socio-economic, ecological and ethical reasons for soil biodiversity management and conservation:

• Soil fertility and agricultural productivity depend on air, nutrient and water cycles as well as on soil structure, which are all closely linked with soil biota (see previous chapter).
• It is estimated that the value of "ecosystem services" (e.g., organic waste disposal, soil formation, N2 fixation, bioremediation and biocontrol) provided each year by soil biota in agricultural systems worldwide may exceed US$ 1,542 billion.
• Ecologically, soil biota are responsible for regulating several critical functions in soil. Excessive reduction in soil biodiversity, especially the loss of keystone species or species with unique functions may have catastrophic ecological effects leading to the long-term deterioration of soil fertility and the loss of agricultural productive capacity.
• On the ethical or moral stance, the intrinsic value, regardless of its potential or actual use, of biodiversity has been stressed by various authors.

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Soil biodiversity and agriculture interact in various ways. Soil organisms may be benefical or detrimental to plant production. Agricultural practices usually induce some changes in the soil environment, resulting in significant modifications of the ratio and interactions of these organisms.

Integrated soil management considers these interactions, aiming to enhance the benefical aspects of soil biota. It includes direct interventions on soil biota (inoculation) and/or interventions on the processes that control the activities of soil biota (mulching, tillage, irrigation, crop rotations).

It has been shown that conventional agriculture relying on tillage and external inputs to enhance productivity may result in greater ecological disturbance, and may be less sustainable in the long term compared to Low External Input Agricultural (LEIA) and/or zero tillage systems. There are many approaches to sustainable agriculture with the goal of reducing environmental degradation, through appropriate technologies or farming techniques. Among these, Organic agriculture and Conservation agriculture are being widely adopted and developed for commercial farming as well as for land reclamation or rehabilitation and food security purposes.

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A seven step process is proposed for the assessment, management and conservation of soil biodiversity in which all the different stakeholders, especially farmers, are involved in each step (adapted from Chambers, 1991; Swift, 1997):

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