Permian Seafloor. Photograph by University of Michigan Exhibit Museum of Natural History.
Extinction is the ultimate fate of all species. The fossil record indicates that more than 95% of all species that ever lived are now extinct. Individuals better adapted to environments are more likely to survive and when a species does fail, it is called a background extinction. Occasionally extinction events reach a global scale, with many species of all ecological types dying out in a near geological instant. Those catastrophic events are known as mass extinctions.
During the last 540 million years five mass extinction events shaped the history of the Earth. The Permian-Triassic mass extinction (PTME) is the most severe biotic crisis in the fossil record, with as much as 95% of the marine animal species and a similarly high proportion of terrestrial plants and animals going extinct . This great crisis occurred 252 million years ago (Ma), and is linked to the emplacement of the large igneous province of the Siberian Traps.
Flow chart summarizing proposed cause-and-effect relationships during the end-Permian extinction (From Bond and Wignall, 2014)
Massive volcanic eruptions with lava flows, released large quantities of sulphur dioxide, carbon dioxide, thermogenic methane and large amounts of HF, HCl, halocarbons and toxic aromatics and heavy metals into the atmosphere. Acid rain likely had an impact on freshwater ecosystems and may have triggered forest dieback. Ocean warming reduced the solubility of oxygen, and raised metabolic rates accelerating the rate of oxygen consumption. Those climatic conditions: global warming, ocean acidification, and marine deoxygenation, are similar to the human-driven environmental disruptions that we are facing today.
An international team of researchers from the California Academy of Sciences, the China University of Geosciences (Wuhan), and the University of Bristol, examined fossils from South China (a shallow sea during the Permian-Triassic transition) and recreated the ancient marine environment using simulated food webs to represent the ecosystem before, during, and after the PTME.
The permian triassic boundary at Meishan, China (Photo: Shuzhong Shen)
The new study indicates that in the first phase of the extinction community stability slightly decreased despite the loss of more than half of taxonomic diversity, while community stability significantly decreased in the second phase (about 60,000 years after the first biodiversity crissis) because ecosystems are more resistant to environmental change when there are multiple species that perform similar functions. Once the last species in each role began to go extinct, the ecosystem rapidly collapsed.
Since the industrial revolution, the wave of animal and plant extinctions that began with the late Quaternary has accelerated. Calculations suggest that the current rates of extinction are 100–1000 times above normal, or background levels. We are in the midst of the so called “sixth mass extinction event”. If we want to stop the degradation of our planet, we need to act now.
References:
Huang, Y., Chen, Z. Q., Roopnarine, P. D., Benton, M. J., Zhao, L., Feng, X., & Li, Z. (2023). The stability and collapse of marine ecosystems during the Permian-Triassic mass extinction. Current Biology. DOI: 10.1016/j.cub.2023.02.007
Bond, David P.G., Wignall, Paul B., (2014). “Large igneous provinces and mass extinctions: An update” https://doi.org/10.1130/2014.2505(02)
Letters from Gondwana. 