New study: Past mass extinctions may hold lessons for today

What the Earth’s environment was like shortly after the mass extinction that killed the dinosaurs about 66 million years ago could help us understand, and prepare for, a future one.

To do that, University of Oregon researchers are teaming up with scientists across the country to study how plant and animal communities recovered in the million years after the late Cretaceous mass extinction. The research could provide insight into how ecosystems will rebuild, and how long it will take, after what could be the sixth mass extinction in Earth history, which many scientists say has already begun and is being caused by human activity.

The Earth has had five mass extinction events, with the most recent happening at the end of the Cretaceous Period about 66 million years ago. The death of the dinosaurs may be the most widely known casualty, but the event resulted in the extinction of 75 percent of species on the planet, which led to a major reorganization of global ecosystems, said Scott Blumenthal, a principal investigator and an assistant professor of anthropology in the College of Arts and Sciences.

“It’s really the last time that we see that in the Earth’s history,” Blumenthal said. “Well, until today, where we have the human impact on the environment.”

The study is supported by a five-year $2.9 million National Science Foundation grant funded by the Frontier Research in Earth Sciences program. Seven institutions are participating in the study, including the Denver Museum of Nature and Science, the University of Colorado Boulder, the University of Wyoming, the City University of New York, Brooklyn College, the College of Charleston and the Smithsonian National Museum of Natural History.

Researchers will focus on the Denver Basin in Colorado and the Williston Basin in North Dakota, both of which have what Blumenthal called “Goldilocks” rock layers, preserving large numbers of fossils from the 1 million years immediately following the late Cretaceous. 

“You don’t get that very often,” Blumenthal said of the unusually complete land plant, mammal and reptile fossils from that period of Earth’s history. “There are very few places where you actually have all of that preserved in rocks that are exposed that we can physically get to.”

Although the late Cretaceous extinction was primarily caused by the asteroid impact, its abruptness is like the human-caused mass extinction that many believe has already begun and will accelerate. Like today, more than 66 million years ago Earth saw a rapid loss rate of biodiversity and rapid changes to global climate.

Prior research by the research team, not including Blumenthal, suggests it took 100,000 to 300,000 years to reach a new ecological equilibrium in the Denver Basin, which is a short slice of the Earth’s history and equals the entire evolutionary timeline of the human species, Blumenthal said.

“What this tells us is the recovery from today’s climate and biodiversity crisis could take a very long time indeed,” he added. 

Blumenthal and his team will spend most of their time at the UO’s Stable Isotope Laboratory, investigating fossilized teeth of early rodent-like mammals. The lab has a laser system that can zap the fossil and emit a puff of dust, which then gets analyzed. 

“That’s going to tell us about their diets, their habitats, as well as how the climate was changing,” Blumenthal said.

But the study isn’t just about what life on Earth was like during the rise of the mammals. It’s also a way to see what the climate looked like more than 66 million years ago, how ecosystems recovered from mass extinctions, and what that means for the current event resulting from biodiversity destruction and climate change. 

“What we hope to learn at the end of all this is what happens on Earth after extinction,” Blumenthal said. “We think what we learn will help us think about conservation priorities today in terms of what would we want to make it through the current crisis.” 

—By Henry Houston, College of Arts and Sciences