Pliocene Reef Gap in the Indo-Pacific

Since the Pliocene Climate Optimum is frequently referenced as a parallel to future conditions, studying the trajectories of Pliocene coral reefs might give insights into the future of Anthropocene reefs. The Coral Triangle and surrounding areas in North Australia are the biodiversity hotspots for Anthropocene reef associated taxa so we assembled a database of all published reef-containing cores from the Miocene, Pliocene, and Pleistocene of the Coral Triangle and North Australia regions and analyzed it for shifts in reef occurrences over time. In the Pliocene, the Coral Triangle and North Australia regions had half as many reefs as they did in the Miocene or Pleistocene. This decline cannot have been driven by temperature since the Miocene was warmer than the Pliocene but likely resulted from local tectonics and possibly fluctuating CO₂ levels. This study also provides a comprehensive stage-level dataset of Pliocene coral reef locations in the Coral Triangle and North Australia which could be combined with models of reef-promoting conditions in the Anthropocene to test models of Pliocene climate.