Ecosystem services from soil

Water sensitive urban design (WSUD) seeks to improve stormwater quality through systems and structures that reduce pollutant loads. Natural or anthropomorphic (human-made) soils perform critical functions in the reduction of pollution, but this role is often poorly understood. The concept of Ecosystem Services has emerged in recent years to assist scientists, designers and engineers take an holistic approach to the design of natural (or re-designed natural) systems and to extract maximum benefit from appropriate use of ecosystem functions. The reduction in pollution load in stormwaters appropriately managed via WSUD is an example of ecosystem function in action. As designers of soils for WSUD systems, we use principles of 'biomimicry' to ensure that the fundamentals of ecosystem function are in place. In practical terms this involves maximising the potential of all site soils to absorb water and adsorb nutrients or pollutants and make them available to microorganisms to engineer their breakdown to more benign substances. Awareness of the complex pathways through which chemical compounds cycle and the soil conditions required to optimise critical reactions must become part of the design 'intelligence' so that ecosystem services provided by these systems are maximised. As an example, stormwater may be rich in nitrogenous compounds, one of which - nitrous oxide - is a potent greenhouse gas, 300 times more damaging than CO2. Strategic design of WSUD soils is necessary to maximise the reduction of such gases from stormwater. Our company has taken a leading role in specifying soils for a range of landscape uses including WSUD. The development of specifications provides guidance to designers with regard to necessary soil properties but also with regard to beneficial uses of site soils to increase the impact of WSUD planning and construction.