What is it about?
We found that Earth switches between two major climate states depending on how widespread coral reefs are. When reefs thrive in shallow tropical seas, the ocean becomes less able to absorb carbon dioxide, slowing recovery after major carbon releases. When reefs collapse, the deep ocean becomes more alkaline and can absorb carbon much faster. These shifts also influenced marine evolution, including the rise of new plankton groups.
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Why is it important?
Understanding this long-term reef–carbon link shows that coral reefs are far more than biodiversity hotspots—they are part of a global system that stabilises climate. As modern reefs decline rapidly, the planet’s carbon cycle may change in ways similar to past reef-collapse events. But although Earth will eventually rebalance, this recovery happens over thousands to hundreds of thousands of years—much longer than human timescales.
Perspectives
Our findings place modern reef decline in a deep-time context. Past reef collapses triggered major shifts in ocean chemistry, climate recovery rates, and marine evolution. Today, human-driven carbon emissions and warming are pushing reefs toward another major collapse—but on a far faster timescale than anything seen in the geological record. This perspective highlights both the resilience of Earth’s long-term systems and the vulnerability of the ecosystems and societies living through the transition. It underscores that while the planet will eventually stabilise, the ecological and human costs of reef loss will be profound and immediate.
Tristan Salles
University of Sydney
Read the Original
This page is a summary of: Carbonate burial regimes, the Meso-Cenozoic climate, and nannoplankton expansion, Proceedings of the National Academy of Sciences, December 2025, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2516468122.
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