Decomposition as a regulating ecosystem service is critical for human well-being and provides a fertile framework to analyze the relationship between faunal diversity and nutrient cycling and energy flux across terrestrial landscapes. Theoretical models and manipulative experiments in laboratory and field have addressed the question of whether species diversity (richness) and abundance has an effect on decomposition, and conversely how the variation in organic matter and biogeochemical dynamics affects faunal soil communities. Most of these studies have suggested a high degree of species redundancy and no subsequent effect on decomposition, although in some cases diversity effects have been demonstrated. Recent experiments conducted at local to global scales are producing an array of information relating faunal diversity to regulation of ecosystem functioning in natural systems. Differences in characteristics of these natural systems indicate the relationships between soil faunal diversity and ecosystem processes vary with climatic type; and the inherent high faunal diversity in some systems present difficulties for validating theory and model results. A recent Global Litter Invertebrate Decomposition Experiment of 30 sites tested whether decomposition rates were affected when fauna were excluded. Results have implications for local and regional decomposition models. Identifying general patterns and testing theory on the relationship between faunal biodiversity and ecosystem processes must consider real-world diversity levels found in soils.