#permian-triassic

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When we think of mass extinctions, we often imagine the meteorite impact that killed the dinosaurs at the end of the Cretaceous, 65 million years ago. However, the greatest extinction event occurred between the Permian and Triassic periods, around 250 million years ago, eliminating over 96% of marine species and about 70% of terrestrial vertebrates. But how did plants fare?

According to a study conducted by University College Cork, the University of Connecticut, and the Natural History Museum of Vienna, plants did not experience a mass extinction comparable to that of animals. Nevertheless, their communities were severely impacted or even completely destroyed due to extreme climatic conditions: intense heat, drought, depletion of the ozone layer, widespread wildfires, and contamination by toxic heavy metals.

The study analyzed fossils from the Sydney Basin in eastern Australia, which at the time was located near the South Pole. Researchers gathered sedimentological data (physical, chemical, and depositional characteristics of sediments), biostratigraphic data (fossil distribution within rock layers), and stable carbon isotope ratios from organic matter, reconstructing environmental conditions of that era.

Fossils revealed that the first plants to recolonize devastated landscapes were conifers. Unfortunately, these conifers did not survive a subsequent period of extreme heat known as the Late Smithian Thermal Maximum, which lasted around 700,000 years. In this hostile environment, stress-tolerant, cosmopolitan lycophytes, similar to modern clubmosses, became dominant. Later, during a cooling event (Smithian-Spathian event), large and unusual seed ferns (such as "umkomasialea") emerged, gradually forming more stable and lush forests. These plants laid the foundation for the Mesozoic dinosaur era and the immense fern-dominated forests that persist in our collective imagination.

This research underscores the importance of protecting modern forests because, as the authors emphasize, "forests eventually recover, but the extinction of individual species is forever." Complete ecosystem recovery takes millions of years, and preserving today's plants ensures stability for future food webs and climate systems.

Pic by Fabien Monteil from Pixabay