The Permian-Triassic (P-Tr) mass extinction that occurred approximately 251 million years ago is the most devastating mass extinction known from the geological record. More than 70% of terrestrial animals, and 80-90% of marine animals became extinct in a time period estimated to be 60,000 years or less. The ultimate cause of the extinction is believed to have been massive surface and subterranean volcanism in the region now called Siberia, and this volcanism in turn drove extreme terrestrial climatic changes, toxification of the atmosphere, ocean warming, ocean acidification, and ocean deoxygenation. The consequences for life were profound. This mass extinction has been of great interest to scientists both because of the ways in which it altered the future course of life on the planet, and also because of the similarity of the extinction drivers to present conditions. Human-driven climate change is creating many of the same processes, including global warming, ocean acidification and so forth. Many questions remain, however, including the timing and the rate at which the extinction proceeded on land, how quickly (or slowly) it affected different types of organisms, and whether the effects were similar across the globe.

In this National Science Foundation Integrated Earth Systems project, we have attempted to develop a detailed understanding of the extinction and its context in a region of northwestern China, the Bogda Mountains. Preliminary geological work shows that this region contains continuous records of the terrestrial transition from the Permian to the Triassic, and hence the time of the extinction. Our goal was to first assemble a transdisciplinary team of scientists who would reconstruct the ancient environment and its changes, including temperature, precipitation, riverine/lake conditions, forest coverage and density, and the fauna, or collection of animals living there at that time. Then this team would use all those data to build a mathematical model of the ecosystem throughout that important interval of time. By doing so, we would gain a better understanding of how the ecosystem was changing, and be able to connect it directly to the changes that were taking place in the environment, including climate.

Unfortunately, our ability to conduct the crucial field work in the Bogda Mountains was interrupted by the COVID-19 pandemic, and after a good field season in 2019, the team has been unable to travel to the region. Nevertheless, we did develop the mathematical model and have applied parts of it to data that were already available for the region, or acquired in our short time there. In this initial report we actually looked at a much longer expanse of time, spanning about 121 million years. The interval includes the P-Tr mass extinction, but also both an earlier and later mass extinction, both considerably smaller than the P-Tr. Our results showed that the P-Tr differed from these lesser mass extinctions in two important ways. First, both of the lesser extinctions were preceded by a lessening of ecosystem stability, whereas the loss of stability during the P-Tr was abrupt. Second, while ecosystem stability recovered rapidly after both lesser extinctions, the P-Tr was followed by a period of prolonged ecosystem instability that lasted at least 5 million years. These observations tell us that mass extinctions can be qualitatively very different, and that recovery from extreme losses of biodiversity can take enormously long periods of time. Both conclusions bear important messages for our present situation, where we face a coupled climate and biodiversity crisis. The project team intends to eventually proceed with the collection of more data, and at that time we will finally be able to peer, in detail, into the mechanisms of the extinction itself, as it unfolded in this part of the world.

Last Modified: 03/06/2023
Modified by: Peter D Roopnarine