My work is multidisciplinary, covering broad areas of rangeland ecology, ecosystem engineering (the effects of organisms on soil processes), soil biology, soil chemistry, restoration ecology and microbiology. The focus of my research is on drylands. Drylands are important because they support about 40% of the global human population, are used extensively for pastoralism, are often centres of human conflict, and are likely to experience substantial changes in land use due to predicted changes in climate. Specifically, my research seeks to understand the relationships among plants, microbes and soil processes and how these change with changes in land use and climate.

I have long-term research interests in the western United States, the Middle East and China. I have four main areas of research:

1. The nature and effects of woody encroachment – Woody encroachment is a global phenomenon whereby grasslands are converted to would land and shrub land, presenting substantial challenges for pastoralists, but opportunities to alter ecosystem services such as hydrology and carbon sequestration.

2. Impacts of herbivore activity – Grazing by domestic and wild herbivores is a substantial land-use in drylands but has considerable impacts on soils, plants, animals and existing functions.

3. Ecosystem engineering – The loss of native soil disturbing animals has been linked to clear reductions in ecosystem functions in drylands, my research aims to quantify these effects and examines the importance of reintroduced animals for restoring degraded ecosystems.

4. Ecology of biological soil crusts – Biocrusts enhance soil function in drylands but are susceptible to overgrazing and changing climates.