Redefining Extinction Impact: Groundbreaking Study Highlights Vulnerability of Terrestrial Ecosystems

Reconstruction of a Late Triassic ecosystem from Ghost Ranch, New Mexico. Published specimens and species preserved at Ghost Ranch were incorporated into the research team’s global ecological dataset. Credit: Viktor O. Leshyk/Natural History Museum of Los Angeles County

Scientists have discovered that terrestrial ecosystems are more prone to collapse from significant animal life loss than marine ecosystems, with the impacts lasting longer on land.

A new study published in Proceedings of the Royal Society B reveals that terrestrial ecosystems were more severely affected by the end-Triassic extinction than marine ecosystems. Furthermore, the recovery period for these terrestrial environments was longer compared to their marine counterparts, a finding that was unexpected. This discovery holds significant implications for the ongoing global extinction event, which is largely driven by human-induced climate change.

“If you remove a significant component of critters from terrestrial ecosystems on land, those ecosystems fall apart and collapse much more easily than what happens in the oceans,” said Dr. Hank Woolley, co-author and NSF Postdoctoral Research Fellow at the Dinosaur Institute. “And secondly, it takes longer for terrestrial ecosystems to recover from a mass extinction event than marine ecosystems.”

Collaborative Research Efforts and Methodology

This project — which was undertaken by Woolley and many other paleoecologists and geologists from NHM and beyond — is the first documented scientific study taking an in-depth look at the end-Triassic extinction event’s effects on both terrestrial and marine ecosystems. In addition to Woolley, NHM Dinosaur Institute PhD students Paul Byrne and Kiersten Formoso (the latter now a newly-minted Presidential Postdoctoral Fellow at Rutgers University), and Postdoc Dr. Becky Wu, co-authored the study with their USC colleagues.

“This research endeavor also combined the expertise of a diverse array of paleobiology, paleoecology, and geobiology researchers at the University of Southern California and the Natural History Museum,” said Dr. Kiersten Formoso. “It’s exciting to get such an assemblage of authors across disciplines to join together to tackle interesting questions about the past and natural world.”

Skeleton of the early dinosaur Coelophysis bauri from the Late Triassic. The protracted restructuring of Early Jurassic terrestrial ecosystems coincided with the diversification of dinosaurs. Credit: Courtesy of Natural History Museum of Los Angeles County

“The traditional marine ecospace framework is really effective and has been widely used in marine paleoecology. So while there are a lot of reconstructions of marine ecosystem change across mass extinctions, we have never been able to study terrestrial ecosystem change in the same way. We hope that this new terrestrial ecospace framework will open the door for future studies comparing how marine and terrestrial communities respond similarly or differently to rapid climate change events,” said co-author Dr. Alison Cribb, now 1851 Research Fellow at the University of Southampton.

“As a research group that studies the paleobiology of life in the oceans and on land, with study systems ranging from billion-year-old stromatolites to dinosaurs, we thought that this would be a unique opportunity to bring our breadth of expertise together to tackle a fascinating and pressing topic—mass extinctions—in a new way,” said Woolley.

While the earliest dinosaurs first appeared and spread more than 230 million years ago during the Triassic period, a catastrophic bout of CO2-fueled global warming led to the end-Triassic extinction event 201.5 million years ago, wiping out around 76% of all marine and terrestrial life. The effects of mass extinction events on marine environments have been well studied by creating ecospaces—3D representations that classify animals by how they feed and move and where they live—but the technique was never applied to terrestrial ecosystems.

Until now, that is.

Findings and Implications

The new team of scientists compiled more than a thousand records from the Paleobiology Database to build the first terrestrial ecospace across the end-Triassic mass extinction. Next, they sorted each occurrence across the three axes to understand how well-represented different groups of animals were in terms of how they survived — eating insects while living mostly in the trees or scavenging for larger animals on the ground, for example. The researchers then took this new framework and compared it to a marine ecospace of the end-Triassic extinction.

Graphic representation of the study concept and findings. Credit: C. Henrik Woolley/Natural History Museum of Los Angeles County

“Our findings reveal that in the wake of the end-Triassic mass extinction, land and sea recovered differently, with land ecosystems experiencing higher extinction severity and taking more time than the oceans to recover groups that filled certain ecological roles. This was because land ecosystems had fewer groups occupying these roles, in contrast with that of the oceans where many taxonomic groups may be doing the same or similar things,” said Formoso.

Their findings could have a stark warning for our modern terrestrial ecosystems as we struggle with growing extinctions in the wake of human-caused climate change. For one thing, the end-Triassic extinction event involved volcanoes spewing out CO2. One of the other takeaways from the results is that no mass extinction event will have the same effects across different ecosystems. Life on land is markedly different—flowering plants are just one group that didn’t exist during the Triassic—but knowing those ecosystems might be even more vulnerable than previously thought should raise alarm bells.

Broader Impacts and Future Directions

“Understanding how life responded to climate change in the past is a major aim of paleontology and one that provides us insight and tools for addressing our modern biodiversity crisis. However, this requires detailed knowledge across a diverse set of organisms, ecosystems, and environments. One of the unique aspects of our collaborative paleontology program at NHM and USC is that it combines an un-motley crew of paleontologists with expertise spanning species, systems, and time – all of which make big-picture studies like this paper possible. As a result, our paleontological impact is greater than the sum of its paleontologists!” says Dr. Nathan Smith, Curator of the Dinosaur Institute at NHM, and Woolley’s PhD and Postdoc supervisor.

The new framework developed for the study could also help scientists better understand mass extinctions across history. That could include our ongoing crisis and possibly inform more effective mitigation and conservation efforts. The collaborative project also demonstrates the value fossils and the fossil record can have when it comes to understanding not just the world of the dinosaurs, but our own rapidly changing climate. “The Natural History Museums of Los Angeles County house millions of fossils spanning the entire history of life,” said Dr. Luis Chiappe, Senior Vice President of Research & Collections, and Gretchen Augustyn Director of the Dinosaur Institute. “Our collections are well-suited to address a wealth of questions related to past and present extinctions.”

Reference: “Contrasting terrestrial and marine ecospace dynamics after the end-Triassic mass extinction event” by Alison T. Cribb, Kiersten K. Formoso, C. Henrik Woolley, James Beech, Shannon Brophy, Paul Byrne, Victoria C. Cassady, Amanda L. Godbold, Ekaterina Larina, Philip-peter Maxeiner, Yun-Hsin Wu, Frank A. Corsetti and David J. Bottjer, 6 December 2023, Proceedings of the Royal Society B.
DOI: 10.1098/rspb.2023.2232