The Status of Soil Macrofauna as Indicators of Soil Health to Monitor the Sustainability of Agricultural Soils

Australian farmers are searching for reliable, easily measured indicators of soil health to monitor sustainability of their enterprises. Over the past five years earthworms have been promoted as indicators of soil health by some researchers. Others have been reluctant to accept soil macrofauna in general as soil health indicators. Their reluctance is based on the difficulty of interpreting biological data in relation to soil health as there is no clear understanding of the links between soil macrofauna and soil health. The problem is further compounded by the inherent difficulty in studying soil biota, inadequate experimental design, and the lack of long term commitment to funding such studies. This paper reflects on current research, and maps out conditions and directions for future research if the role of soil macrofauna in soil health is to be better understood. The compilation of adequate baseline data, the appropriate delineation of experimental plots, attention to the totality of environmental conditions including land management practices, the consideration of impact by other macrofauna, other than earthworms, are some of the directions outlined. The challenge in the future will be to shift the emphasis of soil macrofauna research towards understanding their function in soil processes essential to ecosystem functioning. Without this sort of experimental evidence we can not indicate to the farmer whether the soil resource is declining in quality, stable or in a process of renewal based on the presence of certain macrofauna.