Climatic and tectonic drivers shaped the tropical distribution of coral reefs

TLDR

Warm‑water coral reefs are currently confined to tropical‑to‑subtropical latitudes, whereas historically they extended farther poleward, yet the drivers of these past distributions remain unclear. The study tests how climate and paleogeography have shaped coral reef distribution across geological timescales. The authors combine habitat‑suitability modeling, Earth System simulations, and a 247‑million‑year coral reef fossil record. The analysis shows that climatically suitable reef habitat remained broadly distributed through the Mesozoic‑early Paleogene, narrowed toward the tropics after the late Paleogene due to global cooling and tectonic changes in the Indo‑Australian Archipelago, and that while warming could enable future poleward expansion, reefs are unlikely to keep pace with rapid anthropogenic climate change.

Abstract

Today, warm-water coral reefs are limited to tropical-to-subtropical latitudes. These diverse ecosystems extended further poleward in the geological past, but the mechanisms driving these past distributions remain uncertain. Here, we test the role of climate and palaeogeography in shaping the distribution of coral reefs over geological timescales. To do so, we combine habitat suitability modelling, Earth System modelling and the ~247-million-year geological record of scleractinian coral reefs. A broader latitudinal distribution of climatically suitable habitat persisted throughout much of the Mesozoic-early Paleogene due to an expanded tropical belt and more equable distribution of shallow marine substrate. The earliest Cretaceous might be an exception, with reduced shallow marine substrate during a 'cold-snap' interval. Climatically suitable habitat area became increasingly skewed towards the tropics from the late Paleogene, likely steepening the latitudinal biodiversity gradient of reef-associated taxa. This was driven by global cooling and increases in tropical shallow marine substrate resulting from the tectonic evolution of the Indo-Australian Archipelago. Although our results suggest global warming might permit long-term poleward range expansions, coral reef ecosystems are unlikely to keep pace with the rapid rate of anthropogenic climate change.