Live Science has an interesting piece about refugia during the “Great Dying”.   The End Permian mass extinction was Earth’s worst with an an estimated 80% of life going extinct. A new paper “Refugium amidst ruins: Unearthing the lost flora that escaped the end-Permian mass extinction” in the journal Science Advances, describes a refuge from the disaster unfolding around it some 250 million years ago.

A new study of one of these spots — located in what is now northeastern China —revealed a refuge where the ecosystem remained relatively healthy despite the Great Dying. In this place, seed-producing gymnosperm forests continued to grow, complemented by spore-producing ferns.

“At least in this place, we don’t see mass extinction of plants,” study co-author Wan Yang, a professor of geology and geophysics at the Missouri University of Science and Technology, told Live Science.

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Yang and his colleagues looked at rock layers in Xinjiang that span the mass extinction event.

A major advantage of this now-desert site is that the rocks include layers of ash that hold tiny crystals called zircons. The zircons include radioactive elements — lead and uranium — that gradually decay, which enables researchers to determine how long it has been since the crystals formed. This means the researchers can more accurately date the rock layers here than they can at other sites.

Some of these layers also hold fossil spores and pollen. These fossils reveal that there wasn’t a massive die-off and repopulation but a slow changeover of species, Yang said.

Abstract from “Refugium amidst ruins: Unearthing the lost flora that escaped the end-Permian mass extinction”

Searching for land refugia becomes imperative for human survival during the hypothetical sixth mass extinction. Studying past comparable crises can offer insights, but there is no fossil evidence of diverse megafloral ecosystems surviving the largest Phanerozoic biodiversity crisis. Here, we investigated palynomorphs, plant, and tetrapod fossils from the Permian-Triassic South Taodonggou Section in Xinjiang, China. Our fossil records, calibrated by a high-resolution age model, reveal the presence of vibrant regional gymnospermous forests and fern fields, while marine organisms experienced mass extinction. This refugial vegetation was crucial for nourishing the substantial influx of surviving animals, thereby establishing a diverse terrestrial ecosystem approximately 75,000 years after the mass extinction. Our findings contradict the widely held belief that restoring terrestrial ecosystem functional diversity to pre-extinction levels would take millions of years. Our research indicates that moderate hydrological fluctuations throughout the crisis sustained this refugium, likely making it one of the sources for the rapid radiation of terrestrial life in the early Mesozoic.