Biodiversity triggered the ecological collapse following the “great dying”

The Permian-Triassic extinction event, commonly referred to as the “Great Dying,” which took place 252 million years ago, was the most devastating mass extinction in the history of life on Earth. Although most scientists agree on the cause of this mass extinction, it is still unclear how it happened and how the ecological collapse followed.

Researchers examined marine ecosystems before, during, and after the “Great Dying” in a study that was just published in Current Biology to better understand the chain of events that resulted in ecological instability.

The international study team, which was made up of scientists from the California Academy of Sciences, the China University of Geosciences (Wuhan), and the University of Bristol, discovered that biodiversity loss could be a precursor of a more devastating ecological collapse.

This is a concerning finding given that the current rate of species loss exceeds that of the “Great Dying,” when species were being lost at a faster rate.

The Permian-Triassic extinction serves as a model for studying biodiversity loss on our planet today. In this study, we determined that species loss and ecological collapse occurred in two distinct phases, with the latter taking place about 60,000 years after the initial biodiversity crash.”

Peter Roopnarine, PhD, Academy Curator, Geology, California Academy of Sciences

Nineteen of every twenty species, or 95% of life on Earth, were wiped off by the catastrophe itself. It generated climatic circumstances like the environmental issues caused by humans today, such as global warming, ocean acidification, and marine deoxygenation. It was probably caused by increased volcanic activity and the subsequent rise in atmospheric carbon dioxide.

Researchers used fossils from South China, which had a shallow sea during the Permian-Triassic transition, to reconstruct the ancient marine environment for the study.

The team was able to evaluate prey-predator interactions and ascertain the roles that ancient species played by grouping species into guilds or groupings of species that exploit resources in comparable ways. These hypothetical food chain simulations provide accurate depictions of the ecosystem before, during, and after the extinction event.

The fossil sites in China are perfect for this kind of study because we need abundant fossils to reconstruct food webs. The rock sequences can also be dated very precisely, so we can follow a step-by-step timeline to track the extinction process and eventual recovery.”

Michael Benton, Professor, University of Bristol

Yuangeng Huang, PhD, Academy Researcher who is now at the China University of Geoscience, stated, “Despite the loss of over half of Earth’s species in the first phase of the extinction, ecosystems remained relatively stable.”

In the first phase of the extinction, interactions between species barely changed, but in the second phase, they drastically diminished, leading to the destabilization of ecosystems.

Huang added, “Ecosystems were pushed to a tipping point from which they could not recover.”

When several species fulfill similar roles, an ecosystem as a whole is more resilient to environmental change. As a species goes extinct, another might step in to fill the void, maintaining the ecosystem. This is similar to an economy where the same service is offered by several businesses or organizations.

The service and economy continue to function even when one firm goes out of business, but if the service is monopolized by one organization, the opposite will happen.

Roopnarine further added, “We found that the biodiversity loss in the first phase of the extinction was primarily a loss in this functional redundancy, leaving a sufficient number of species to perform essential function. But when environmental disturbances like global warming or ocean acidification occurred later on, ecosystems were missing that reinforced resistance, which led to abrupt ecological collapse.”

The study team’s results emphasize the need of taking functional redundancy into account when evaluating current conservation measures and serve as a timely reminder of the need to take immediate action to alleviate the current human-driven biodiversity crisis.

Huang concluded, “We are currently losing species at a faster rate than in any of Earth’s past extinction events. It is probable that we are in the first phase of another, more severe mass extinction. We cannot predict the tipping point that will send ecosystems into total collapse, but it is an inevitable outcome if we do not reverse biodiversity loss.”