New Insights into the Permian Mass Extinction and Its Possible Triggers
A collaborative group of researchers from Shandong University of Science and Technology, Nanjing University, and several other Chinese scientific institutions has proposed a compelling explanation for the largest mass extinction in Earth’s history. This event occurred at the end of the Permian period, about 252 million years ago, and their conclusions appear in the scientific journal Chemical Geology (ChemGeo). The study synthesizes paleontological, geochemical, and atmospheric modeling data to outline a scenario in which life on Earth faced unprecedented stress from a cascade of environmental shocks.
The extinction event profoundly reshaped life on both land and sea. Estimates suggest that roughly 81% of marine species and around 70% of terrestrial vertebrate species vanished. The plant kingdom did not escape unscathed; many plant lineages suffered dramatic changes, with surviving vegetation showing signs of stress and mutation in the wake of the catastrophe.
The researchers point to intense volcanic activity as a likely driving force behind the Permian crisis. Massive volcanic eruptions would have released vast amounts of gases into the atmosphere, contributing to the destruction of the ozone layer and triggering a sequence of harmful processes. Key impacts include the infiltration of the atmosphere with toxic hydrogen sulfide and the onset of widespread acid rain, alongside disruptions in the global oxygen balance that fed into ocean deoxygenation.
Evidence supporting this volcanic scenario comes from geochemical analyses. The team detected elevated sulfur isotope concentrations in microscopic pyrite grains recovered from late Permian rock deposits. These isotope shifts, captured using mass spectrometry, point to chemical changes in the atmosphere that would accompany a strong ultraviolet (UV) light regime and altered sulfur cycling in the oceans.
The proposed mechanism involves a surge of UV radiation following ozone loss. Modeling efforts indicate a substantial drop in atmospheric oxygen from about 30% during earlier Phanerozoic times to roughly 15% by the end of the Permian. This oxygen decline would have stressed aerobic life forms, while supporting a shift toward anaerobic and sulfide-producing microbial communities in marine environments.
In this scenario, sulfate-reducing bacteria in the oceans likely proliferated under anoxic conditions, reinforcing sulfide-rich conditions that proved lethal to many marine organisms and contributed to a broader ecological collapse spanning several habitats. The combination of oceanic stagnation, toxic gases, and UV exposure created a hostile world in which survival depended on rapid adaptation or relocation to refugia that remained relatively hospitable.
Fossil records also reveal adaptive responses in plants, including the presence of ultraviolet-protective substances in Permian-era pollen. This indicates that terrestrial flora experienced selective pressures from increased UV radiation and other atmospheric stressors, shaping evolutionary trajectories in the plant kingdom long after the extinction pulse.
Overall, the study presents a picture of a singular and catastrophic environmental upheaval driven by rampant volcanism, ozone depletion, and dramatic shifts in atmospheric and ocean chemistry. While other factors may have contributed to the Permian extinction, the integration of geochemical signals with atmospheric models offers a persuasive explanation for how this ancient disaster unfolded and why it could have been so devastating for life on Earth. (Source: Chemical Geology; cited by the authors)