Current Ocean Crisis Indicates Land May Be Experiencing Even More Stress

New research from an international team of scientists led by Colby College Professor of Geology Robert Gastaldo appears this week in Nature Communications, the world’s leading multidisciplinary science journal. Titled “The base of the Lystrosaurus Assemblage Zone, Karoo Basin, predates the end-Permian marine extinction,” the publication of the paper in this prestigious journal once again highlights Colby’s deep expertise and excellence in the sciences.

Leaf of Glossopteris, the most common and dominant southern hemisphere tree before ecosystem disturbance in the late Permian. Photo courtesy of M. Grey, Joggins UNESCO World Heritage site, Nova Scotia.

The research, which was funded by the National Science Foundation, reveals that at the time when planet Earth experienced the greatest loss of biodiversity, during what is known as the end-Permian mass extinction about 251.9 million years ago, biodiversity on land suffered several hundreds of thousands of years before biodiversity crashed in the ocean.

“If changes in biodiversity on land preceded the biodiversity changes in the ocean during the Great Dying, which is what our paper shows, the current changes that we’re now seeing in the ocean may mean we’re close to reaching a major tipping point and crisis on land,” said Gastaldo, the Whipple-Coddington Professor of Geology at Colby. “In other words, not only are the plants and animals on land the canary in the coal mine, but the canary may already be threatened or, at the very least, quickly approaching an imbalance. The bottom line is that, while we’ve largely focused on the crisis in the ocean and how it will, or could, affect organisms on land, there is now solid evidence that land may be the first to respond.”

Gastaldo added that the timing of the turnover seems to be coincident with the beginning of massive volcanic activity that occurred in what is now Siberia. Over the course of less than one million years, this volcanic episode emplaced a volume of lava and other igneous rocks approaching 720,000 cubic miles. Those rocks now cover 80 percent of Siberia. This activity significantly increased atmospheric gas concentrations, including carbon dioxide, methane, sulfur, and mercury. “Essentially what was happening then is what we’re seeing now—a massive release of damaging gases that alter the way in which Earth systems operate,” he said. 

With the publication of this paper, the turnover in vegetation across the landscape in the Southern Hemisphere during the end-Permian mass extinction—including the loss of a major group of seed plants that formed extensive forests—has now been documented in both Australia and South Africa at the same time.

Skull of Lystrosaurus maccagi, a common Late Permian synapsid tetrapod in the Karoo Basin, South Africa, held by Robert Gastaldo for scale. Specimen in the collections of the Albany Museum, Grahamstown, South Africa. Photo courtesy of R.A. Gastaldo.

“We are incredibly proud of Bob’s ongoing accomplishments and congratulate him on having his research published once again in such a prestigious publication,” said Margaret McFadden, provost and dean of faculty at Colby College. “His work is reflective of science programs that are unparalleled for a small liberal arts school and that are truly having an impact by addressing the major issues and challenges affecting our world.”

This is the third time that Professor Gastaldo has been published in Nature. His most recent article in the journal, “Ancient plants escaped the end-Permian mass extinction,” discussed what happened to terrestrial plants during the end-Permian crisis.