Nature often hints at large events before they arrive, and scientists have long studied signs that precede mass extinctions. The most recent and dramatic example occurred about 183 million years ago, when rapid changes in the oceans and shifts in essential trace elements foreshadowed a global collapse of life. This ancient crisis involved a sharp rise in oceanic carbon dioxide levels followed by a decline in metals crucial to marine and planetary ecosystems, culminating in a mass die-off during the early Jurassic period. As a result, a vast majority of ocean-dwelling species and a substantial portion of land-dwelling species disappeared, driven by higher atmospheric and oceanic carbon concentrations than previously estimated.
A key pattern identified by researchers is a significant jump in carbon dioxide dissolved in seawater, followed by a drop in trace metals necessary for biological processes. These metals become scarce in oxygen-poor, sulfur-rich conditions that inhibit the normal redox reactions that keep life thriving in marine environments. The pattern points to a critical link between chemical shifts in the oceans and the loss of biodiversity during ancient extinction events.
same thing now
Beyond the data showing the metal decline, scientists emphasize that the magnitude of carbon cycling between sea and air was likely larger than earlier estimates. One author notes that current trends could push carbon levels in the ocean and atmosphere to unprecedented scales if human activities continue unabated, potentially mirroring the upheaval seen in the distant past.
Illustrations and reconstructions accompany the study, including depictions of how ancient oceans responded to changing chemistry. The researchers highlight how a drop in molybdenum, a biologically important micronutrient, is tied to broader shifts in ocean chemistry and carbon storage. In modern contexts, this relationship is part of the broader discussion about how rising atmospheric CO2 affects marine ecosystems and global climate.
Re-creating ancient conditions helps scientists visualize the connections between trace metals and carbon in the oceans. In the study area, rocks from sites in the western region of Canada offered a window into the global ocean that once surrounded the supercontinent Pangea. These rocks, once part of a vast sea, enable researchers to infer the broader climate and chemical dynamics of the era.
A decrease in molybdenum signals a rise in oceanic organic carbon, reaching levels that strained life in the ancient seas. The team’s calculations suggest that the ocean’s CO2 concentration during the event was significantly higher than previous models indicated, prompting a reevaluation of past estimates in light of volcanic and tectonic activity that shaped carbon release.
The analysis indicates that molybdenum reduction preceded the onset of the extinction by roughly a million years, with the entire die-off lasting about two million years. Recovery after such events tends to be slow, often taking hundreds of thousands of years as ecosystems rebuild and adapt. These timelines underscore how deep the impact of climate and chemical shifts can be on global biodiversity.
The modern climate change trajectory bears echoes of ancient patterns. The current trajectory shows rising CO2 levels in the atmosphere and ongoing oceanic changes, raising concerns about parallel outcomes in the future. Some researchers caution that the planet could experience disruptions in essential micronutrients like molybdenum, which would further threaten marine life and ecosystem stability.
This evidence adds weight to the argument that historical events can inform present-day risks. The possibility of a sixth global extinction is discussed in the context of human activities, highlighting the urgency of addressing environmental changes to safeguard biodiversity.
Reference work: AGU Developments, 2022. A detailed exploration of CO2, molybdenum, and extinction dynamics is available through the researchers’ publication.
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