The End-Permian extinction, occurring approximately 252 million years ago, was the most severe biodiversity crisis in Earth’s history. Often called “The Great Dying,” this event defines the boundary between the Permian and Triassic periods, fundamentally altering the course of life. The extinction unfolded with remarkable speed in geological terms, with the bulk of species loss happening in less than 200,000 years. This event reshaped the planet’s ecosystems, setting the stage for a new chapter in the history of life.
Life Before the Great Dying
During the late Permian, the planet’s landmasses were consolidated into the supercontinent of Pangaea. This massive continent experienced a range of climates, with vast, arid interiors and more temperate conditions along its extensive coastlines. Life on land was dominated by synapsids, the group that includes the ancestors of mammals. Among them were the formidable gorgonopsians, saber-toothed predators that occupied the top of the food chain, alongside other large herbivores and amphibians.
The oceans of the Permian teemed with complex and diverse ecosystems. Reefs were built not by the corals we know today, but by different groups known as rugose and tabulate corals. The seas were also home to unique invertebrates. Trilobites, a highly successful group of marine arthropods, had already existed for over 250 million years, while sea scorpions, or eurypterids, were formidable aquatic predators. These marine environments supported a wide array of life, from brachiopods and crinoids to shelled cephalopods.
The Cataclysmic Causes
The primary trigger for the mass extinction is considered to be a colossal volcanic event in the Siberian Traps. This was not a single eruption but a series of massive lava flows that continued for up to two million years, covering vast areas of modern-day Russia. The eruptions released immense quantities of greenhouse gases, including carbon dioxide, directly into the atmosphere. This process was amplified as the hot lava ignited extensive coal deposits, releasing even more carbon dioxide and methane.
This massive injection of greenhouse gases initiated a cascade of environmental calamities. The planet experienced extreme global warming, with average ocean temperatures rising by as much as 8°C (14.5°F). As the oceans warmed, they lost their ability to hold dissolved oxygen, leading to widespread anoxia and disrupting circulation patterns. The absorption of atmospheric carbon dioxide also led to significant ocean acidification, making it difficult for marine organisms to build their skeletons and shells. The volcanic eruptions also released sulfur dioxide, which produced acid rain that damaged terrestrial ecosystems.
The Toll of Extinction
The environmental devastation resulted in an unprecedented loss of biodiversity. Scientists estimate that the event wiped out approximately 96% of all marine species and 70% of terrestrial vertebrate species. In the oceans, entire groups of animals vanished forever. The trilobites, which had survived for hundreds of millions of years, were completely eliminated, as were the rugose and tabulate corals that formed the era’s reefs. This collapse was so complete that reef-building ceased for about 14 million years.
Other marine groups, such as blastoids and sea scorpions, also disappeared entirely. On land, the devastation was equally severe. The dominant synapsids, including the fearsome gorgonopsians, were decimated, and entire forests collapsed. The End-Permian extinction is also notable for being the only mass extinction to have a significant impact on insects, a group that has otherwise proven remarkably resilient throughout Earth’s history.
The Aftermath and Recovery
In the wake of the widespread collapse, the planet was populated by “disaster taxa”—hardy, generalist species that could survive in the harsh, low-diversity environment. The most prominent example is the pig-sized synapsid Lystrosaurus, a herbivore whose fossils are found globally in post-extinction rock layers, indicating its widespread success in the depopulated world.
The recovery of complex ecosystems was an incredibly slow process, taking millions of years. The profound loss of species left countless ecological niches vacant. This massive ecological reset paved the way for a new group of animals to rise to prominence. The archosaurs, the group that includes crocodiles, birds, and dinosaurs, diversified and filled the roles left empty by the synapsids, setting the stage for the dawn of the Age of Dinosaurs.