Oxygen levels in the Earth’s atmosphere started declining during the transition from the Permian period to the Triassic period. This decline is believed to have occurred approximately 250 million years ago. It is important to note that the exact timing and magnitude of the decline are still subject to ongoing research and debate among scientists.
The Permian period was marked by abundant plant life and high levels of atmospheric oxygen. However, a series of catastrophic events, including volcanic eruptions and the formation of large-scale coal deposits, resulted in a significant release of carbon dioxide into the atmosphere. This led to a rapid increase in global temperatures and a decrease in oxygen levels.
Robert Berner, a researcher at Yale University, conducted carbon-cycle modeling to estimate the changes in atmospheric oxygen levels during this period. His calculations suggest that oxygen levels began to decline soon after the onset of the carbon dioxide release, reaching about 16 percent at the end of the Permian.
The decline continued into the Triassic period, with oxygen levels bottoming out at less than 12 percent about 10 million years into this period. This significant drop in oxygen levels had profound effects on the Earth’s ecosystems, leading to the extinction of many marine and terrestrial organisms.
It is worth mentioning that the decline in oxygen levels was not solely caused by the increase in carbon dioxide. Other factors, such as changes in ocean circulation patterns and the proliferation of oxygen-consuming bacteria, likely contributed to the decline as well.
Understanding the timing and extent of the decline in oxygen levels is crucial for comprehending the ecological and evolutionary consequences of this period in Earth’s history. It is through the study of past events like this that scientists can gain insights into how changes in atmospheric composition can impact the planet’s biodiversity.
While the decline in oxygen levels during the Permian-Triassic transition may seem like a distant event, it offers valuable lessons for our current understanding of environmental change. By studying past episodes of oxygen depletion, scientists can better comprehend the potential consequences of ongoing human activities, such as deforestation and the burning of fossil fuels, which also have the potential to alter atmospheric oxygen levels.
Oxygen levels in the Earth’s atmosphere began declining during the Permian-Triassic transition, approximately 250 million years ago. Carbon-cycle modeling suggests that the decline started soon after a significant release of carbon dioxide into the atmosphere, reaching about 16 percent at the end of the Permian and dropping to less than 12 percent about 10 million years into the Triassic period. Further research is needed to refine our understanding of the timing and magnitude of these changes, but studying past episodes of oxygen depletion provides valuable insights into the potential consequences of environmental change.