The plant-eating pareiasaurs were preyed on by sabre-toothed gorgonopsians. Both groups died out during the end-Permian mass extinction, or “The Great Dying.” CREDIT: © Xiaochong Guo

Yuangeng Huang was a recent post-doctoral researcher in my lab at the California Academy of Sciences. Several years ago, while conducting his Ph.D. research at the China University of Geosciences (CUG) in Wuhan, Yuangeng trekked over to the United States and spent about six months in my lab, where he learned a great deal about the sorts of paleoecological modeling that we do. Then after completing his Ph.D., he joined me in my lab in the fall of 2019 as a post-doc. This was ideal, as part of Yuangeng’s dissertation research was on late Paleozoic and early Mesozoic terrestrial faunas from the Xinjiang region of China, which coincided with a large collaborative project in the Integrated Earth Systems program at the US NSF, of which I am a part. Yuangeng and I had great plans for the coming year, but of course 2020 was anything but a normal year. Unfortunately Yuangeng spent much of his time in the COVID-19 lockdown, along with most residents of the California Bay Area. Nevertheless, we adjusted as had so many other people around the world, and we did manage to do some very nice work, in my opinion. Yuangeng headed back to Wuhan in the fall of 2020 to take up a new position at CUG.

The first product of our time together is a recent paper published in the Royal Society Proceedings B, entitled “Ecological dynamics of terrestrial and freshwater ecosystems across three mid-Phanerozoic mass extinctions from northwest China“. In the paper we examined a span of 121 million years, comparing three mass extinctions: the end-Guadalupian event, the end Permian, and the Triassic-Jurassic transition. The end Permian mass extinction is by far the most severe recorded in the geological record. We compared the stabilities of terrestrial-aquatic communities within this span by reconstructing functional networks and food webs of the communities, and using mathematical models to subject them to disruptions of primary productivity (photosynthesis). The results of such perturbations are disruptions of populations, and eventually extinctions as the magnitude of the perturbations increases. What we found is that the two smaller events struck at times when communities were at relatively lower stability compared to the end Permian, but that recovery after the latter event was significantly more prolonged. This is yet a bit more evidence of the uniqueness of the end Permian extinction and the Permian-Triassic transition. Interestingly our results here are consistent with results for similar examinations of coeval communities from the Karoo Basin of South Africa, despite those communities being both taxonomically and ecologically different from the Xinjiang communities.

Comparing the stabilities of late Palezoic and early Mesozoic communities from northwest China (Huang et al., 2021). “Collapse threshold” is the point at which a community collapses when subjected to disruptions of primary productivity.

The paper is the result of a great collaboration, led by Yuangeng, involving researchers from China (including Yuangeng’s dissertation advisor, Zhong-Qiang Chen), the United States (including Wan Yang and myself), and the United Kingdom (Michael Benton). There are important communities from these times preserved elsewhere in the world (Russia, Brazil, Australia), giving us the potential to eventually truly understand the dynamics underlying these important events in biodiversity’s history.

And here is the link to a very nice commentary from the great science communications team at the Academy, “How Life on Land Recovered After “The Great Dying” Mass Extinction Event.”