'Life oasis' provided refuge for plants during Earth's worst extinction event

A region in China’s Turpan-Hami Basin served as a refugium – or “life oasis”- for terrestrial plants during the end-Permian mass extinction. This event is widely recognized as the most severe biological crisis since the Cambrian period. 

The discovery of this life-saving refuge, which is detailed in a recent study, challenges the longstanding belief that land-based ecosystems experienced catastrophic losses on par with marine environments at that time.

Evidence of a “life oasis” on land

The research team was led by Professor Liu Feng from the Nanjing Institute of Geology and Palaeontology (NIGPAS) of the Chinese Academy of Sciences.

According to Professor Feng, the Turpan-Hami Basin offered a protective area where terrestrial plant communities remained largely intact. 

Rather than succumbing to widespread die-off, these plant populations continued evolving, ultimately facilitating a more rapid ecological recovery. Thus, these pockets of resilience played a crucial role in the rebound of life on Earth.

Reevaluating the end-Permian crisis

Occurring roughly 252 million years ago, the end-Permian mass extinction decimated over 80% of marine species. However, its impact on terrestrial life has been less certain. 

One common explanation is that catastrophic volcanic eruptions in Siberia caused extreme conditions, including wildfires and toxic gases. 

Researchers previously based this theory on the progressive loss of the Gigantopteris flora in South China and the Glossopteris flora across Gondwanaland around the same time as the extinction.

Opposing views argue that the lethal effects were not universal, but limited by latitude and atmospheric circulation. Some fossil evidence suggests certain Mesozoic plant species actually predating the extinction, pointing to gradual transitions rather than abrupt collapse.

Examining ancient pollen and spores 

Central to the study’s discoveries is the South Taodonggou section in Xinjiang Province.

The researchers examined ancient pollen and spores and using precise radiometric dating based on a Bayesian age model developed by Professor Yang Wan of the Missouri University of Science and Technology.

The team detected an unbroken record of riparian fern fields and coniferous forests spanning from 160,000 years before the extinction started to 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,” said Wan Mingli, a scientist at NIGPAS.

The evidence implies that certain plants vanished locally, but the overall loss of spore and pollen species in the South Taodonggou section could have been about 21% – much lower than the known marine extinction level at the time. 

Many seemingly extinct species reappeared in Early Triassic layers elsewhere, indicating they may have migrated rather than disappeared altogether.

Rapid recovery and ecological diversity

A stable vegetation foundation apparently sped up ecological resurgence in this “life oasis.” 

Fossil data shows that just 75,000 years after the extinction ended, the region already supported a range of terrestrial vertebrates, such as the herbivorous Lystrosaurus and carnivorous chroniosuchians. 

This contradicts earlier assumptions that ecosystems took over a million years to recover following the end-Permian extinction. In this area, it happened more than ten times faster.

The researchers attribute such resilience to the region’s semi-humid climate and steady rainfall, evaluated through paleosol analysis.

The Turpan-Hami Basin consistently received around 1,000 millimeters of precipitation annually, providing lush vegetation and an environment beneficial to migrating wildlife.

Despite its apparent proximity to volcanic activity believed to have spurred the extinction, the basin functioned as a safe haven for terrestrial life, illustrating how even seemingly threatened areas can preserve crucial biodiversity.

Surprising pockets of resilience

“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 said. 

The existence of such a shelter for plants during the crisis calls into question the scope and uniformity of land-based mass extinctions. In some locales, climates and landscapes worked in concert to protect certain species from the worst consequences.

As modern science grapples with the possibility of a sixth mass extinction – potentially driven by human impacts – these findings underscore the importance of discovering and safeguarding present-day refugia. 

By identifying environments where life can endure, even amid large-scale devastation, conservationists might replicate and preserve these safe harbors for future generations.

The study was published in the journal Science Advances.

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