It is often assumed that freshwater macroinvertebrates in anthropogenically impacted catchments are a subset of those found in unimpacted catchments. However, recent evidence suggests re-evaluation. Here we present the results of a survey of eighteen streams in Tasmania within catchments that have gradients of forestry and agricultural impacts. Alpha diversity varied greatly in unimpacted and forestry sites but was capped in sites with > 20% of catchment conversion to agriculture. Overall beta diversity was primarily driven by species replacement instead of the loss of a group of species. Forestry sites tended to contain a limited number of species also occurring in natural sites, but the species found in agricultural sites were mostly different to those found in natural sites, suggesting that turnover is greatest in catchments with higher agricultural conversion.