Recognising and responding to the influences of agriculture and other land-use practices on soil fauna in Australia

The abundance and diversity of soil fauna are influenced by a wide range of agricultural and other land use practices. This paper provides three Australian examples of the ways in which land use has affected the different components of the soil fauna and discusses strategies that might be applied to respond to these changes. The paper also discusses an emergent issue (genetic engineering of plants) which may prove to have implications for the soil fauna in future. European settlers dramatically altered the earthworm fauna when they established agriculture on the Australian landscape. This change in the fauna, from native megascolecids to introduced lumbricids, happened by chance, not through thoughtful management. Whilst the most common species now present have the potential to enhance soil properties and plant production significantly, they are patchy in distribution, generally rare in numbers and poor in behavioural diversity. Adoption of the management practices which increase earthworm abundance (e.g. reduced tillage and stubble retention), redistribution of beneficial species to regions lacking them and the introduction of more appropriate taxa from overseas may improve the current fauna's performance. Mediterranean helicid snails are introduced pests of pastures, croplands and vineyards in southern Australia. Their pest status has increased due to the adoption of agricultural practices aimed at soil conservation. Molluscicides are prohibitively expensive to use regularly on a broad-acre basis and environmentally undesirable. Strategic use of such chemicals, as strips to interrupt the seasonal movements of snails or in years when the snail numbers are particularly high, may provide a useful alternative. Fragmentation of native forests is common in Australia but the impact of this fragmentation on the abundance and diversity of soil fauna is poorly understood. Preliminary results are presented for the effects of fragmentation of a Eucalyptus forest on a millipede community. Responses vary between species of soil invertebrates, illustrating that studies need to be focused at population rather than community levels. Responses also vary in time, indicating the need for long-term assessments. Genetically-engineered plants are being developed which incorporate toxins to kill leaf feeding insects. The non-harvested parts of such plants serve as food for the soil fauna which drive nutrient recycling processes. The suitability of this plant material for processing by the soil fauna needs to be researched. (C) 1998 Elsevier Science B.V.