Paleoart reconstruction of the Lower Triassic Heshanggou Formation coastal mudplain to alluvial ecosystem in North China. Image credit: J. Sun (CC BY-SA 4.0)
For over half of its history, Earth was an unwelcoming place devoid of oxygen and rich in carbon dioxide, methane and water vapor. Yet some of the earliest forms of life are thought to have emerged around 3.7 to 4.28 billion years ago, and life began to flourish during the Cambrian explosion around 500 million years ago.
Over millions of years, life was repeatedly tested and reshaped by five major mass extinctions. The largest of these, around 252 million years ago, wiped out over 95% of marine species and 70% of land or terrestrial species. Intense volcanic activity, global warming, acid rain, and elevated levels of carbon dioxide and sulfur rendered Earth a hostile environment once again for millions of years.
How long it took for environments and organisms to recover remains debated. While some marine species appear to have rebounded relatively quickly, much less is known about terrestrial species due to scarce fossil records, particularly in equatorial land basins.
To investigate if animals and plants in these regions recovered slowly or rapidly, Guo et al. analyzed rock formations from the uppermost Permian-Lower Triassic layer of the Shichuanhe, Dayulin and Liulin sections, as well as the Hongyatou, Tuncun, Mafang outcrops in the Central North China Basin.
The researchers identified newly discovered medium-sized carnivores, plant stems, and root traces. Improved ichnological criteria (methods used to study trace fossils such as burrows, tracks, and feeding marks) and significantly increased infaunalization (the extent to which organisms live within sediments) from the Heshanggou Formation of the central North China Basin suggest a relatively complex, multi-level feeding-structure within a river-associated ecosystem during the Spathian stage, just two million years after the mass extinction. This suggests that terrestrial ecosystems in equatorial regions may have recovered more rapidly and with greater complexity than previously assumed.
The study deepens our understanding of how Earth became habitable again and offers new perspectives on how life responds to extreme global warming. It suggests that, around 250 million years ago, plants and animals adapted relatively quickly to hyperthermal conditions, for example by burrowing and inhabiting riparian environments, providing valuable insights into potential biological responses to future climate change.
