The loss of biodiversity may be the harbinger of a more devastating ecological collapse, an international team of scientists has discovered.
By exploring the stability and collapse of marine ecosystems during the Permian-Triassic mass extinction, researchers have gained troubling insights into the modern biodiversity crisis, as the rate of species loss exceeds the current rate during the event, known as the ‘Great Death’.
The history of life on Earth has been marked by several mass extinctions. The largest of these, the Permian-Triassic extinction, occurred 252 million years ago. While scientists generally agree on its causes, exactly how this mass extinction unfolded, and the ecological collapse that followed, remains a mystery.
In a study published today in current biologyThe international study team, made up of researchers from the University of Bristol, the California Academy of Sciences, the University of Geosciences of China (Wuhan) analyzed marine ecosystems before, during and after the Great Dying to better understand the series of events that led to ecological destabilization.
They examined fossils from southern China, a shallow sea during the Permian-Triassic transition, to recreate the ancient marine environment. By classifying species into guilds, or groups of species that exploit resources in similar ways, the team was able to analyze prey-predator relationships and determine the functions that ancient species performed. These simulated food webs provided plausible representations of the ecosystem before, during, and after the extinction event.
“The fossil beds in China are perfect for this type of study because we need abundant fossils to be able to reconstruct food webs,” said Michael Benton, a professor at the University of Bristol. “In addition, rock sequences can be dated very precisely, so we can trace step by step along the crisis when life in the oceans died from heat shock, ocean acidification, and loss of oxygen from the ocean. seabed, and then through the recovery steps of life.”
“The Permian-Triassic extinction serves as a model for studying biodiversity loss on our planet today,” said Academy curator of geology Peter Roopnarine. “In this study, we determined that species loss and ecological collapse occurred in two distinct phases, with the latter occurring about 60,000 years after the initial collapse in biodiversity.”
The event itself wiped out 95% of life on Earth, or around 19 out of 20 species. Likely triggered by increased volcanic activity and a subsequent increase in atmospheric carbon dioxide, it caused climate conditions similar to the human-driven environmental challenges seen today, namely global warming, acidification of the oceans and marine deoxygenation.
“Despite the loss of more than half of Earth’s species in the early phase of the extinction, ecosystems remained relatively stable,” explained the Yuangeng Huang Academy researcher, now at the China University of Geosciences. . Interspecies interactions decreased only slightly in the first phase of the extinction, but decreased significantly in the second phase, leading to destabilization of ecosystems. “Ecosystems were pushed to a tipping point from which they could not recover,” Mr. Huang continued.
An ecosystem as a whole is more resilient to environmental change when there are multiple species performing similar functions. If one species goes extinct, another can fill that niche and the ecosystem remains intact. This can be compared to an economy where multiple companies or corporations provide the same service. The demise of a corporation still leaves the service and the economy intact, but the opposite will occur if the service is monopolized by a single entity.
“We found that the loss of biodiversity in the early phase of extinction was primarily a loss in this functional redundancy, leaving sufficient numbers of species to perform essential functions,” said Dr. Roopnarine. “But when environmental disturbances such as global warming or ocean acidification occurred later, ecosystems lacked that bolstered resilience, leading to abrupt ecological collapse.”
For the study team, their findings emphasize the importance of considering functional redundancy when evaluating modern conservation strategies and remind them of the urgent need for action to address today’s human-driven biodiversity crisis.
“We are currently losing species at a faster rate than in any of Earth’s previous extinction events. We are likely in the first phase of another, more severe mass extinction,” added Dr. Huang. “We cannot predict the tipping point that will cause total ecosystem collapse, but it is an inevitable outcome if we don’t reverse biodiversity loss.”
Paper:
‘The stability and collapse of marine ecosystems during the Permian-Triassic mass extinction’ by Peter Roopnarine, Mike Benton et al in current biology.