Is the loss of Australian digging mammals contributing to a deterioration in ecosystem function?

Despite once being described as common, digging mammal species have been lost from the Australian landscape over the last 200 years. Around half of digging mammal species are now extinct or under conservation threat, and the majority of extant species have undergone marked range contractions. Our aim is to identify the role of digging mammals in ecosystem processes throughout Australia. We highlight how the actions of digging mammals are vital for maintaining ecosystem functioning and how their extirpation has led to loss of ecosystem functions. A review of the literature indicates that many aspects of the influence of bioturbation on ecosystem functioning have been studied. The role of digging mammals in arid and semi-arid zones has been previously established. We collate and review a broader scope of studies, including those carried out in the mesic woodlands and forests of Australia. We identify roles of digging mammals in the context of ecosystem functioning and conservation management. Bioturbation significantly alters soil processes, increasing soil turnover and altering the chemical and structural properties of soil. Greater water infiltration and decreased surface run-off and erosion alter soil hydrophobicity and increase soil moisture. Diggings capture organic matter, provide habitat for a diversity of microscopic and macroscopic organisms, and increase nutrient cycling. Mycophagous mammals disperse fungi (e.g. mycorrhizae), while all diggings can create suitable sites for fungal growth. Diggings also capture plant seeds, increasing seedling germination, recruitment and plant growth. The overall effect of mammal diggings is therefore increased plant vigour and resilience, increased biodiversity and consequently improved ecosystem functioning. We propose that the loss of digging mammals has contributed to the deterioration of ecosystems in Australia. Recognising the roles of digging mammals will inform potential management options such as species translocations or reintroductions.