University of Bristol: Biodiversity loss drove ecological collapse after the ‘Great Dying’, new study reveals
Biodiversity loss may be the harbinger of a more devastating ecological collapse, an international team of scientists have discovered.
By exploring the stability and collapse of marine ecosystems during the Permian-Triassic mass extinction, researchers have gained worrying insights into the modern biodiversity crisis, given that the rate of species loss today outpaces that during the event, known as the ‘Great Dying’.
The history of life on Earth has been punctuated by several mass extinctions. The largest of these, the Permian-Triassic extinction event, 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 Biology, the international study team—composed of researchers from the University of Bristol, California Academy of Sciences, the China University of Geosciences (Wuhan) analysed 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 South China—a shallow sea during the Permian-Triassic transition—to recreate the ancient marine environment. By sorting species into guilds, or groups of species that exploit resources in similar ways, the team was able to analyse prey-predator relationships and determine the functions ancient species performed. These simulated food webs provided plausible representations 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 so we can reconstruct food webs,” said Bristol’s Prof Michael Benton from the University of Bristol. “Also, the rock sequences can be dated very precisely, so we can track step by step all through the crisis when life in the oceans was killed by heat shock, ocean acidification, and loss of oxygen from the seabed, and then through the steps of recovery 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 taking place about 60,000 years after the initial biodiversity crash.”
The event itself wiped out 95% of life on Earth, or about 19 out of every 20 species. Likely triggered by increased volcanic activity and a subsequent spike in atmospheric carbon dioxide, it caused climatic conditions similar to the human-driven environmental challenges seen today, namely global warming, ocean acidification, and marine deoxygenation.
“Despite the loss of over half of Earth’s species in the first phase of the extinction, ecosystems remained relatively stable,” explained Academy researcher Yuangeng Huang, now at the China University of Geosciences. Interactions between species decreased only slightly in the first phase of the extinction but dropped significantly in the second phase, causing ecosystems to destabilize. “Ecosystems were pushed to a tipping point from which they could not recover,” Mr Huang continued.
An ecosystem as a whole is more resistant to environmental change when there are multiple species that perform 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 several companies or corporations provide the same service. The demise of one corporation still leaves the service and economy intact, but the opposite will occur if the service is monopolized by a single entity.
“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 functions,” Dr Roopnarine said. “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.”
For the study team, their findings stress the importance of considering functional redundancy when assessing 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 past extinction events. It is probable that we are in the first phase of another, more severe mass extinction,” Dr Huang added. “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.”