Soil resilience

Soil resilience refers to the ability of a soil to resist or recover their healthy state in response to destabilising influences. This is a subset of a notion of environmental resilience. Soil resilience should first be looked at in terms of soil formation and development (pedogenesis), a continuous process taking thousands of years – this puts into context the short time that humans have so extensively utilised, changed and depended directly on soil. Pedogenesis is the result of five factors: the first two are parent material and topography, which are passive and contribute to soil mass and position; the next two are climate and the biosphere, which are active and supply the energy in soil formation. Finally, there is time. It is the active factors in soil formation that vary so as to constitute an environmental change or shock. Over time, variations have been significant: Over millions of years the soil has endured varying atmospheric conditions including a complete absence of oxygen and associated behaviour of soil elements in a reducing environment, and the establishment of life – particularly of terrestrial vegetation 420 million years ago. Over ten thousand years and following the last ice age, though average climate has remained relatively stable, the soil has faced periods of extended wet, dry and fire. If soil were not resilient, then in the face of past influences it would not be in any condition to support the natural and commercial services that we expect of it currently. So what do we expect of soil resilience? Constant or evolving state? – Do we expect that the soil to remain constant – to continue to provide the same environmental and commercial services as at present, or; that it will establish a new equilibrium? How long will it take? – How long do we expect soils to ‘hold out’ or adjust, and are we realistic about pedological time? In Australia, the above questions are relevant given the strong dependence on the soil, yet the significant degradation of soils over little more than 200 years due to adoption of European styled agriculture.