A Resilient Ocean: New Insights into Mass Extinction Recovery
The Earth has experienced five major mass extinction events, periods of catastrophic species loss driven by global change. Scientists now believe we are on the precipice of a sixth. Understanding how ecosystems rebound from such devastation is therefore critical, and a recent study led by David Jablonski at the University of Chicago is challenging long-held assumptions about the recovery process following the most recent extinction - the end of the Cretaceous period.
This event, famous for wiping out the dinosaurs, eliminated over three-quarters of all species. Jablonski’s team focused on marine mollusks – shellfish, oysters, and others – due to the excellent fossil record provided by their durable shells. By meticulously reconstructing the ecological landscape before the extinction and comparing it to the species present afterward, they uncovered a surprising result: despite the massive loss of life, the fundamental ecological structure of the marine environment remained remarkably intact.
“If 75% of all species are extinct, you would expect that at least a few ways of life would be entirely lost, leaving only one or two species to fill those roles,” explains Katie Collins of the London Natural History Museum. ”But that’s not what we see.”
This finding contradicts previous theories about extinction recovery. For decades, some scientists believed mass extinctions simply accelerated pre-existing evolutionary trends – dinosaurs were destined to be replaced by mammals, and the asteroid impact merely sped up the process. Others proposed that extinctions acted as a selective pressure, favoring species capable of evolving to fill newly available niches.
Jablonski’s research doesn’t support either of these ideas. He views the results as a warning,highlighting a gap in our understanding of how biodiversity loss impacts ecological function. “we do not understand how the loss of functional groups relates to the loss of biodiversity,” he states.
further complicating the picture, the study revealed that the species which did survive didn’t necessarily thrive in a predictable manner. Contrary to expectations,survivors didn’t uniformly capitalize on opportunities and rapidly diversify. While this pattern might hold true for mammals, Jablonski found it wasn’t the case in marine ecosystems, with recovery appearing more random.
This research has meaningful implications for modern ocean conservation. With the seas facing threats like acidification, pollution, and overfishing, understanding how ecosystems respond to large-scale disruption is paramount. Jablonski emphasizes the need to consider the broader ecological structure, not just individual species, when developing management policies and establishing marine reserves. ”This is something we really want to understand if we want to discuss modern extinction and recovery in the ocean, as well as how to manage it,” he explains. “Billions of people depend on the sea for food, and we can see that nature reserves and management policies need to consider the wider biota ecological structure, not just individual species.”
The study,published in Science Advances on May 21,2025,is titled “The end-Cretaceous mass extinction restructured functional diversity but failed to configure the modern marine biota.”
(Original Content)