Global change, phase-shifts and recovery potential of Tasmania’s rapidly warming reef ecosystems

Global change is causing phase-shifts from healthy to collapsed reefs across temperate systems worldwide. On the rapidly warming coasts of Tasmania, subtidal monitoring of rocky reef ecosystems reveals cascading changes over the past 30-years. From widespread loss of giant kelp forests to the formation of extensive sea urchin barrens, the transformation of local reef-scapes has been profound. In this presentation, I will highlight long-term changes in reef fishes and invertebrates and explore the transition between surface-canopy giant kelp forests and lower-canopy kelp beds, and ultimately collapse to persistent urchin barren grounds. I will contrast monitoring trends inside/ outside marine protected areas and supplement this with long-term spatially extensive field experiments that reveal the ecological mechanisms, including reduced natural predation and range-extending herbivores plus altered dominance hierarchies of competing kelps, that are driving phase-shift and creating feedbacks locking-in alternative states. I will conclude by discussing how our collective monitoring and experimental understanding is now being used to reinstate critical ecosystem functioning safeguarding temperate reefs against collapse, and how this combined approach to understanding natural history is leading to important opportunities for scaling-up ecosystem restoration.