REVIEW: Potential roles of soil fauna in improving the efficiency of rain gardens used as natural stormwater treatment systems

Abstract

Summary Natural treatment systems such as rain gardens aim to overcome the negative effects of urbanization on water quality, availability, and freshwater and marine ecosystem integrity by mimicking the natural water cycle in urban planning and design. While soils in these systems are inhabited by a diverse array of invertebrates, the soil macrofauna is ignored in the vast majority of studies on new or existing rain gardens. Here, we review the functional roles of invertebrates commonly found within soils of rain gardens. Soil fauna have the potential to substantially alter plant growth, water infiltration rates, and the retention and removal of pathogens, nutrients, heavy metals and other contaminants. Their lack of inclusion in controlled laboratory or greenhouse studies may contribute to differences in observed function in field and laboratory settings. Promising future research directions include the following: (i) the use of controlled experiments to study invertebrate effects on rain garden function; (ii) determining the factors affecting variability in organismal abundance among and within sites; and (iii) the design of rain gardens to facilitate development of fauna that promote desired functions. Synthesis and applications. Soil fauna may substantially alter the function of rain gardens as natural stormwater treatment systems in urban areas. Therefore, incorporat‐ing animal effects into design and testing may better enable managers and researchers to understand and optimize rain garden functioning, and forecast the longevity of rain gardens.