The international journal Nature Geoscience recently published a paper that provides a new explanation behind the first mass extinction, known as the Late Ordovician mass extinction. The study suggests that climate cooling changed the ocean’s circulation pattern, disrupting the flow of oxygen-rich water from shallow seas to deeper portions of the ocean. This disruption led to a widespread loss of marine life.
Understanding Mass Extinction Events
A mass extinction event is a phenomenon where species disappear at a much faster pace than they are replaced. Typically, such events involve around 75% of the world’s species being lost within a geologically short timeframe, roughly less than 2.8 million years.
A Brief History of Mass Extinctions
To date, five major mass extinction events have occurred throughout Earth’s history. These include:
– The first mass extinction, the Ordovician, happened approximately 445 million years ago and resulted in the loss of about 85% of all species.
– The second, the Devonian mass extinction, took place about 375 million years ago and wiped out approximately 75% of the world’s species.
– The third, known as the Great Dying or the Permian mass extinction, occurred around 250 million years ago, exterminating over 95% of all species.
– The fourth, the Triassic mass extinction, unfolded about 200 million years ago, eliminating nearly 80% of Earth’s species, including some dinosaurs.
– The fifth and most famous, the Cretaceous mass extinction, occurred roughly 65 million years ago, leading to the eradication of non-avian dinosaurs.
The Latest Research Findings
There have been numerous theories postulated about each mass extinction event, with recent advances in technology assisting researchers in uncovering more detailed insights. Traditionally, it was thought that volcanism-induced global warming led to oceanic oxygen depletion, threatening marine habitability and ecosystem stability.
However, new evidence suggests that Earth’s oxygen levels have also dropped during periods of climate cooling. The study of the Ordovician climate and marine biogeochemical cycles indicated “seafloor and upper-ocean oxygenation in response to ongoing global cooling.” This situation resulted in deep-sea anoxia affecting ocean circulation. Consequently, the researchers concluded that climate cooling likely led to alterations in nutrient cycling and primary producer communities, crucial factors driving the Late Ordovician mass extinction.
The Potential Sixth Mass Extinction and Its Implications
Some scientists believe that we are currently in the midst of a sixth mass extinction, brought on by human-induced climate change, often called the Anthropocene extinction. It’s estimated that only 2% of all species that ever existed are still alive today, but the absolute number of species is higher than ever before.
The loss of species can result in significant impacts, such as a reduction in crop pollination and water purification. Moreover, if a species plays a specific role in an ecosystem, its loss can have ripple effects throughout the food chain, drastically altering entire ecosystems and reducing their genetic and cultural variability. Such biodiversity losses can, in turn, diminish the contribution of these ecosystems to human welfare.
Last Modified: February 13, 2024