Rocky reefs of New South Wales (NSW) are characterised by a mosaic of habitats, including kelp forest and urchin-grazed barrens. These habitats support a diversity of dependent species. Decades of research have demonstrated that kelps form extensive forests with distinctive fish and invertebrate faunas and the ‘barrens’ boulder habitat provides shelter and other resources for commercial fishes, charismatic fishes and invertebrates; the barrens are not deserts! The feeding activities of herbivorous invertebrates, particularly the black sea urchin (Centrostephanus rodgersii) determine the presence of barrens habitat. Some invertebrates survive only in the presence of urchins and are the food resources for many predatory fishes. The barrens habitat in NSW has been highly stable for decades and is critical for the diversity of reef-based organisms. Because of climate change, Tasmanian waters have warmed and as a result C. rodgersii larvae have dispersed southward from NSW. Importantly, the situation regarding C. rodgersii in Tasmania differs from the established pattern in NSW and this needs to be recognised in the approach to management of this species in the two states. Urchins in NSW should be appreciated as important habitat determiners and the removal of them for whatever purpose would have to be managed carefully.