December 12, 2023

Collapse of land-based ecosystems led to devastation of marine life during Permian mass extinction

New research reveals timeline of the annihilation of life on earth 252 million years ago

A new paper has shed light on the immense impact that global warming and deforestation can have on land and marine environments, leading to the mass extinction of virtually all living eco-systems.

A team of geologists and palaeontologists, including Senior Professor Guang Shi from the University of Wollongong’s (UOW) School of Earth, Atmospheric and Life Sciences, examined the end-Permian mass extinction event, which occurred approximately 252 million years ago. They found that protracted global warming and volcanic activity cleared the land in an act of mass deforestation. This led to the demise of the terrestrial, or land-based, ecosystem, which in turn directly caused the devastation of marine ecosystems.

The timeline of events, and the order in which the respective ecosystems experienced catastrophic collapse, has previously been extremely difficult for scientists to unravel. 

Published in Evolving Earth, the paper was co-authored by Professor Vivi Vajda and Dr Ashley Krüger from the Swedish Museum of Natural History in Stockholm; Professor Kliti Grace from Curtain University;  and Dr Sangmin Lee and Professor Shi from UOW.

Using fossil and geological records drawn from the western and eastern coasts of Australia, including at Coalcliff in NSW, directly under the Sea Cliff Bridge, the researchers determined that the mass death of plants, most likely caused by a warming Earth, led to widespread and devastating erosion on land.

Over time, nutrients and sediments from the land leached into the ocean in vast amounts, leading to the mass extinction of marine ecosystems due to lack of oxygen. Essentially, the collapse of the terrestrial ecosystem eventually suffocated aquatic life.

Professor Shi said the research finally enabled scientists to accurately construct a timeline for the collapse of the terrestrial and marine ecosystems in Australia that led to the end-Permian era extinction, the biggest mass extinction event in history.

“It has been extremely difficult to determine which of these two ecosystems were impacted first and how the demise of one ecosystem affected another,” Professor Shi said.

“In our study, for the first time, we were able to use the fossil record of spores and pollen, both from ancient land plants, and algae preserved in marine and terrestrial sediments to correlate and determine the order of events across the Australian continent, as it existed 252 million years ago.

“The age correlation using these micro plant fossils, which are very tiny, is essential for this work because Eastern Australia only has rock records of this mass extinction that represent terrestrial ecosystems that were deposited in vast coastal swamps and river systems. These terrestrial deposits are today reflected in our extensive coal deposits such as Bulli Coal, whereas in Western Australia only marine rock records spanning this mass extinction are available.

“We found that mass extinction of land plants in eastern Australia occurred earlier, probably by hundreds of thousands of years, than the extinction of the marine ecosystem in Western Australia. The mass death of land plants in Australia at the time resulted in widespread land-surface erosion and the influx of land-derived nutrients into oceans or coastal marine ecosystems, causing algae blooms in marine ecosystems, ultimately leading to severe oxygen-deficiency in marine ecosystems and finally mass dying of marine organisms.”

The Permian mass extinction led to the death of approximately 90 per cent of all species on Earth, including animals, insects, plants, and fungi. While scientists have not pinpointed the exact cause of the global end-Permian mass extinction, Professor Shi said it is linked to large-scaled, protracted global warming and intense volcano eruptions.

^{Dr Sam Lee and Professor Guang Shi, pictured at UOW's Wollongong Campus.}

Professor Shi said the research provides a greater insight into the historically and geologically important Permian extinction and offered lessons into how climate change could impact the planet, and its countless species, organisms, creatures, and ecosystems, in the future.

“This scenario is strikingly similar to what is happening to our Murray-Darling river system today, where episodic mass mortality of fish occurs during times of flooding due to an overabundance of nutrients, warming and lack of oxygen.

“Though the timescale is different, the phenomenon and the ecological process leading to mass dying is very similar. The implication is that widespread deforestation has a significant potential impact on aquatic ecosystems, such as rivers, lakes and oceans, going well beyond the realm of terrestrial ecosystems.”

In their paper, the research team drew on work that had previously been undertaken right in Professor Shi and Dr Sangmin Lee’s backyard, near Wollongong.

“The Coalcliff rock section is one of the best exposures of rock layers in Australia, where the transition from pre-extinction through the post-extinction vegetation and landscape types is exceptionally well preserved and can be directly observed and studied.

“The availability of these high-quality rock layers spanning this mass extinction event is very rare on a global scale.”