Most often celebrated for their dazzling biodiversity, coral reefs have more recently been found to have played a profound role in orchestrating the rhythm of Earth’s carbon and climate cycles for more than 250 million years.
These are the groundbreaking new findings published this week in the scientific journal, Proceedings of the National Academy of Sciences (PNAS) in which researchers have showed that the rise and fall of shallow-water reef habitats have dictated how quickly the planet rebounded from major carbon dioxide disturbances.
Researchers from the University of Sydney and Université Grenoble Alpes combined plate-tectonic reconstructions, global surface-process models, climate simulations, and ecological modelling to trace shallow-water carbonate production all the way back to the Triassic Period.
Their analysis reveals that the Earth system oscillates between two distinct modes – each setting the pace of climate recovery.
“Reefs didn’t just respond to climate change – they helped set the tempo of recovery,” said lead author Associate Professor Tristan Salles of the University of Sydney’s School of Geosciences.
When tropical shelves are expansive and reefs flourish, carbonate accumulates in shallow seas, limiting chemical exchange with the deep ocean. This weakens the “biological pump” – the process by which marine organisms draw down carbon – and slows the planet’s rebound from CO₂ ‘shocks’.
By contrast, when reef space collapses due to tectonic shifts or sea-level change, calcium and alkalinity build up in the oceans. Carbonate burial migrates to the deep sea, boosting nannoplankton productivity and accelerating climate recovery.
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