Researchers have discovered a clue in Italian limestone that helps explain a mass extinction of marine life millions of years ago and may provide warnings about how oxygen depletion and climate change could impact today’s oceans. The study, published in the Proceedings of the National Academy of Sciences, measured oxygen loss in oceans leading to the extinction of marine species 183 million years ago during the Jurassic Period. This extinction event occurred due to volcanic activity in modern South Africa, which released an estimated 20,500 gigatons of carbon dioxide over 500,000 years, heating the oceans and causing them to lose oxygen.
The research provides important insights into how oxygen depletion in ancient oceans led to mass extinctions, serving as an analog for predicting future oxygen loss in oceans from human-made carbon emissions. By studying limestone sediment that carries chemicals dating back to the time of the volcanic outburst, researchers were able to estimate the change in oxygen levels in ancient oceans. They found that at one point, oxygen was completely depleted in up to 8% of the ancient global seafloor, an area roughly three times the size of the United States.
Since the Industrial Revolution began in the 18th and 19th centuries, human activity has released CO2 emissions equivalent to 12% of what was released during the Jurassic volcanism. However, the current rapid rate of atmospheric CO2 release is unprecedented in history, making it difficult to predict when another mass extinction might occur or how severe it might be. The researchers emphasized that the severity of the current situation poses significant challenges in determining the potential impacts of rapid CO2 emissions on marine ecosystems and biodiversity.
While the past extinction event serves as an important analog for understanding the effects of oxygen loss in ancient oceans, researchers acknowledge that it is not a perfect comparison to the rapid CO2 emissions occurring today. Despite efforts to quantify marine oxygen loss during the Jurassic event, uncertainties remain regarding the timing and severity of future mass extinctions caused by current human-made carbon emissions. Michael A. Kipp, an assistant professor at Duke University and co-author of the study, emphasized the importance of utilizing historical data to constrain predictions of future oxygen loss and its impacts on marine ecosystems.
Overall, the study highlights the interconnected nature of past and present climate events, emphasizing the importance of understanding ancient extinction events to predict and mitigate the impacts of current human-induced climate change. By studying the link between volcanic activity, oxygen depletion, and mass extinctions in ancient oceans, researchers aim to provide valuable insights into the potential consequences of ongoing CO2 emissions on marine life and biodiversity. The findings underscore the urgent need for global action to reduce carbon emissions and mitigate the impacts of climate change on marine ecosystems.