The remote locale that shielded plants during Earth's biggest mass extinction
During a cataclysmic mass extinction event, there are typically not many places to hide. However, a region of the mountainous Turpan-Hami Basin in the Xinjiang Autonomous Region in Western China may have been an oasis for some living organisms during the planet's largest mass extinction. The spot may have served as a refugium–or life oasis–for terrestrial plants during the end-Permian mass extinction, when 80 to 90 percent of life on Earth was wiped out about 252 million years ago.
These new findings are detailed in a study published March 12 in the journal Science Advances and challenges some of the views that land-based ecosystems saw the same major losses as marine environments during this incredibly turbulent time in our planet's natural history.
During the end-Permian mass extinction––also called the Great Dying–80 percent of marine species were wiped out. While most species on land did not fare much better, the scope of terrestrial impacts has been debated by scientists.
One prevailing theory suggests that massive volcanic eruptions in present-day Siberia triggered widespread devastation on land through wildfires, acid rain, and toxic gases. The extinction of Gigantopteris plants in South China and across the ancient supercontinent Gondwanaland around 252 million years ago helps bolster this argument.
[ Related: Mega El Niños helped kill 90 percent of life on Earth. ]
However, another theory argues that latitude and atmospheric circulation may have limited the effects of acid rain, wildfire, and toxic gases in certain regions. Some fossils suggest that some Mesozoic plants even existed before the mass extinction event, which could be evidence of uninterrupted evolution.
In this new study, a team of scientists from institutions in the United States, Tibet, and China used fossil evidence of a terrestrial plant community that appears to have remained largely intact throughout the extinction event. This allowed the plants to continuously evolve and recover from any losses more quickly.
The team looked at the South Taodonggou section of the Turpan-Hami Basin in Xinjiang. They used detailed analysis of fossil pollen and spores and a new geological dating method developed by Missouri University of Science and Technology geologist Wan Yang. From this dating technique and fossil analysis, it appears that the riparian fern fields and coniferous forest here continually thrived from 160,000 years before the extinction event began until 160,000 years after it ended.
'The presence of intact tree trunks and fern stems further confirms that these microfossils represent local vegetation, not transported remnants,' Mingli Wan, a study co-author and paleobotanist at the Nanjing Institute of Geology and Palaeontology (NIGPAS) of the Chinese Academy of Sciences, said in a statement.
While some plant species did disappear locally, the team found that the overall extinction rate of spore and pollen species in South Taodonggou may have been only 21 percent. This percentage is significantly lower than the marine extinction rate during the same period, which saw about 80 percent of life wiped out.
According to the team, this stable base of vegetation was crucial for the local ecosystem's recovery. Fossil evidence shows that this area was home to numerous tetrapods, small four-limbed vertebrates that include today's living amphibians, reptiles, birds, and mammals. The region was home to a plant eating tetrapod called Lystrosaurus and carnivorous chroniosuchians, which shows that the food web became more complex fairly quickly. The new evidence suggests the area recovered more than 10 times faster than in other regions of the world.
The area's stable, semi-humid climate may have been the reason behind this great biological resilience. South Taodonggou consistently received about 100 millimeters of rainfall per year, which helped build abundant vegetation and a more habitable environment than other regions after the end-Permian mass extinction. All of this plant life offered vital support for migrating animals.
Its proximity to the volcanic activity that triggered the end-Permian extinction also allowed the Turpan-Hami Basin shelter for crucial biodiversity.
'This suggests that local climate and geographic factors can create surprising pockets of resilience, offering hope for conservation efforts in the face of global environmental change,' Feng Liu, a study co-author and paleontologist at NIGPAS, said in a statement.
According to the authors, the current concerns about the planet entering another mass extinction–one driven by human activity–highlights the importance of identifying and protecting areas like this that could protect life.
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