Dr. Yuehan Lu's team at the University of Alabama has rewritten the story of one of Earth's worst extinction events—and it turns out the villain wasn't fire, but the ocean itself slowly suffocating. About 370 million years ago, during the Late Devonian period, vast coastal regions began losing oxygen, choking marine ecosystems across the globe. For decades, researchers suspected that massive wildfires sweeping across continents had triggered this catastrophe. But a meticulous study published in Science Advances in April 2026 reveals the opposite: the ocean collapse came first, and the wildfires were its consequence.
The breakthrough came from an unusually precise examination of a shale deposit in Chestnut Mound, Tennessee. By analyzing chemical signals and fossil biomarkers—organic molecules preserved in rocks that serve as fingerprints of ancient organisms and processes—Lu's team reconstructed the sequence of environmental changes with unprecedented temporal resolution. What they found was stark: indicators of marine anoxia, or oxygen-depleted conditions, appeared in the geological record first, followed distinctly by signals of terrestrial wildfire activity. This direct evidence settled a question that had eluded science for years, primarily because earlier researchers had gathered samples from different geographic locations and lacked the precise dating needed to establish clear timing.
The mechanism behind this cascade is both elegant and sobering. When ocean anoxic events occur and marine life dies on a massive scale, organic material sinks to the ocean floor and gets buried under sediment instead of decomposing and releasing carbon into the atmosphere. In normal cycles, this carbon eventually binds with atmospheric oxygen to form carbon dioxide. But when it's sequestered on the ocean floor, the balance of atmospheric oxygen tilts dangerously upward. Higher oxygen concentrations make vegetation more flammable and fuel more frequent, intense wildfires. The fires, in other words, were the ecosystem's response to an oxygenated atmosphere created by the very ocean collapse that had preceded them.
Strikingly, this oxygen-driven surge in wildfire activity didn't end when the mass extinction itself subsided. The research shows that elevated fire activity persisted long afterward, evidence of a profound, lasting shift in Earth's atmospheric conditions. The Late Devonian period is recognized as one of the five great extinction events in Earth's history—a moment when the planet's tightly interlocked systems of ocean, atmosphere, and land fundamentally altered their relationship with one another.
The implications ripple forward to our own time. As modern climate change shifts carbon cycling and alters wildfire regimes, understanding how these deep-time feedbacks operate becomes essential for scientists trying to anticipate future environmental responses. The Devonian story demonstrates that Earth's systems are far more tightly coupled than simple cause-and-effect suggests. Changes in one realm can cascade invisibly through others, reinforcing one another over timescales that dwarf human lifespans. The oxygen that kindled ancient forests was born from an ocean crisis—a reminder that the systems sustaining life today are equally interconnected, and equally fragile.