Jim Steele (@JimSteeleSkepti) recently put out a great X post.
Here’s the heart of it:
The”Great Dying”, or end Permian mass extinction, is considered to have happened between just 251.9 and 251.8 million years ago.
Although there is no scientific consensus on its cause, in keeping with the current crisis narratives, many researchers blame the loss of 81% of marine species and 70% of terrestrial vertebrate species existing at that time on high CO2 concentrations released by the Siberian Taps volcanic events around 251.9 million years ago.
But Permian extinctions had been elevated long before that.
Likely due to researchers being biased by the abrupt extinction event when an asteroid collision ended the Age of Dinosaurs, mass extinction events have been arbitrarily defined as a short-lived die-off. However, such an artificial time constraint on extinction processes is now being challenged by the modern concept of “Dead Clades Walking”.
Researchers are increasingly finding mass extinction events are triggered by various detrimental events that happened 10 to 100 million years earlier. Narrowly focusing on events happening 252 million years ago, totally obscures the drivers of extinction.
As illustrated in the graphic above, Bambach shows before modern times, the evolution of new genera relative to extinctions was greatest during the Devonian 400 million years ago when CO2 levels hovered between 4000 & 2000 ppm and global average air temperature was estimated at 22.4°C, much higher than the 20th century average of 13.9°C.
As CO2 decreased, so did the number of genera.
When the framework of “Dead Clades Walking” is applied to the end-Permian extinctions, CO2 starvation emerges as the driver. CO2 starvation reduces photosynthesis and the productivity needed to support entire food webs. The end-Permian extinctions were the culmination of greatly reduced biodiversity happening over the previous 50 million years, resulting from reduced photosynthesis.
As shown above by Kroeck (2022), very few new phytoplankton species ever originated during the late Carboniferous and Permian as CO2 concentrations plummeted to 100 to 200 ppm by the early Permian, its lowest levels ever.
The resulting series of small extinctions throughout the Permian were punctuated by the larger extinction events mentioned below, culminating in the end-Permian’s deadly finality.
~305 MYA – Late Carboniferous:
With coal beds sequestering carbon and lowering atmospheric CO2 to starvation levels, Carboniferous tropical rainforests collapsed.
Similarly early stages of a controversial “phytoplankton blackout” appeared (see figure below), named for the extremely low diversity and abundance of phytoplankton fossil evidence. Clearly the base of the earth’s food webs was being devastated.
~300-265 MYA – early Permian:
As CO2 starvation reduced photosynthesis, it also reduced oxygen concentrations from its high of 35%, then falling far below today’s 20% by end Permian.
Giant insects and skin-breathing fish-like amphibian creatures (Lepospondyli) that had evolved and adapted to high oxygen levels in the Carboniferous quickly went extinct. Terrestrial animals were limited to low altitudes due to lack of oxygen at higher elevations.
Low oxygen levels persisted into the Triassic and likely prevented any timely recovery from the Permian’s extinctions.
~273 MYA -Early-Mid Permian Olsen’s mass extinction:
Plant genera fell by 25%; highest rates of reptile-like (Eureptilia ) extinctions, exceeding the end-Permian mass extinction rates.
High rates of amphibian and fish extinctions also observed.
~259 MYA – mid Permian Capitanian mass extinctions:
74-80% loss of South African tetrapod generic richness; 56% of plant species went extinct; 24% of plant species went extinct in South China.
Researchers who denied the phytoplankton blackout evidence had based their arguments on “the presence and abundance of filter feeding and suspension feeding benthic organisms such as brachiopods, crinoids, sponges and corals” suggesting there was undetected adequate primary production.
However, particulate and dissolved organic matter and the bacterial loop likely maintained those marine food webs for millions of years after initial phytoplankton collapse.
The effects of a phytoplankton blackout finally became evident by the Capitanian with the extinction of 35% to 47% of all marine invertebrate genera, 82.2% of coral species, 82% of fusulinacean foraminifers and 87% of brachiopods.
251.9 – 251.8 MYA – end-Permian Great Dying:
It began over 50 million years before, when low CO2 dramatically reduced photosynthesis and began dead clades walking and with greatly reduced biodiversity the end-Permian gave its last gasps.
For a deeper dive into all this, watch Jim Steele’s video on YouTube: “How CO2 Starvation & Plate Tectonics Caused the Greatest Mass Extinction, the Permian Great Dying”.