Around 251 million years ago, the greatest mass extinction in history occurred.
Between the Permian geological period and the Triassic, the Earth suffered the greatest devastation of biodiversity loss it has ever seen. It is estimated that 90-95% of marine life and 75% of terrestrial species died out, and it is the only known mass extinction of insects.
Ecosystems took 30 million years to recover.
During the Permian, the Earth contained two large land masses – Pangea and Siberia – which were surrounded by a global ocean called Panthalassa.
The Permian era was the final in the Paleozoic era and lasted from 299 million years ago to 251 million years ago. Due to Pangea’s immense land size, there were severe extremes in the climate – from great seasonal fluctuations between the North and South, while other regions were submerged under ice caps.
Possible causes of the mass extinction event are widespread and likely causally connected. Some of these include the eruption of the Siberian traps, meteors, climate change, and ocean anoxia.
1 – METEORS
A series of meteor attacks occurred during this time. Evidence of meteoric fragments can be found in the Falklands crater, as well as a crater in Antarctica (caused by a space rock more than twice as big as the one causing the demise of the dinosaurs), and a crater found off the coast of Australia.
2 – VOLCANISM
According to a group of researchers, the Siberian Traps (a large region of volcanic rock) were a massive contributor to the end-Permian extinction. Explosive eruptions of lava over the land and flowing beneath the surface began around 300,000 years before the beginning of the end-Permian extinction, and created immense sheets of igneous rock in the shallow crust of the Earth. As this region erupted, magma rose up through the Earth’s crust (magmatism), essentially ‘cooking’ sediments in its path, and releasing copious amounts of greenhouse gases, like carbon dioxide and methane into the atmosphere.
3 – GREENHOUSE GASES
The release of greenhouse gases caused global temperatures and sea levels to fluctuate. This rapid climate change meant species were not adapted to such conditions.
Carbon dioxide and methane release also resulted in ocean anoxia. This proved a double-edged sword for oceanic creatures since oxygen uptake increases with temperature rise, but oxygen solubility decreases in warmer water. Therefore, there was a decline in oceanic circulation as temperatures differed and decreased between the poles and equator.
4 – WILDFIRES
Researchers discovered that, alongside the increase of CO2 in the environment, widespread wildfires may have contributed to end-Permian global warming, triggering soil erosion and rendering much of the land arid and inhospitable.
The first phase of the end-Permian extinction was land-based; the second phase was marine-based, and the third phase was land-based.
RECOVERY AFTER THE EXTINCTION
Initially, global diversity rose sharply, as disaster taxa (organisms that populate a region after a (short-term) natural disaster/mass extinction) filled empty guilds (a group of species that have similar requirements and play a similar role within a community).
This brought about restructured communities with the loss of browsers and predators and an increase in piscivores. The loss of browsers is linked to changes in vegetation.
However, Permian levels of plant diversity were not reached again until the Late Triassic, 230 million years ago.
THE FUTURE OF EARTH…
We are currently walking the path towards the 6th mass extinction.
Unlike the previous mass extinctions on Earth, our current loss of biodiversity is a direct result of human activity: unsustainable use of land, water and energy, and climate change.
However, such categorising – “biodiversity”, “climate change”, “deforestation” – is a divisive attempt by humans to understand complex, interrelated systems. As George Monbiot has written, ‘Nature recognises no such divisions. As Earth systems are assaulted by everything at once, each source of stress compounds the others.’
If we do not affect significant changes to our way of living, we will continue losing life-sustaining biodiversity, and our ecologies will be unable to support life.
For more on what to do about the sixth mass extinction, see here.
See also: ‘Regenesis’ (2022) by George Monbiot for a discussion on the current food system and associated environmental destruction, through a fascinating examination of soil ecology.