Soil erosion – The impact of grazing and regrowth trees

Abstract

It is well recognised that excessive soil erosion is a significant environmental issue for disturbed landscape systems. This is particularly the case for agriculture, where soil loss is not only a source of pollution but impacts soil fertility and sustainability. In recent years, improved pasture management, rotational grazing and holistic management practices have been employed and it is generally believed that soil erosion has been reduced to acceptable levels. For many landscapes, there has been a lack of ecological diversity and trees have been planted or allowed to regrow to provide ecological services as well as provide shade and windbreaks. However, in many circumstances, observed grass cover is reduced leaving soil exposed. While these practices are well-accepted, there has been little assessment of their impact on soil erosion and general soil properties. Here, we examine a grazing (pasture) landscape typical of many on the east coast of Australia and calculate erosion rates using an environmental tracer. We find that with the current management practices the soil loss is relatively low (<5 tonnes/ha/yr). However, it is likely to be an order of magnitude greater than soil production rates. Regrowth trees maintained to provide shelter and ecological services did not result in higher soil loss despite observed and measured reduced ground cover both under and surrounding the tree plot.