A new study published in the Proceedings of the National Academy of Sciences reveals that marine life flourishes with a wave of new species every 36 million years, with tectonic growth being an indirect cause. The research team led by geologist Sala Bouilla from Sorbonne University in France found that "this disrupts many ecosystems, causing competition among numerous species, which allows new species to thrive to fill new ecological niches that emerge."
Geologist Dietmar Müller from the University of Sydney states, "The 36-million-year cycle represents changes between faster and slower ocean floor spreading, leading to periodic changes in depth within ocean basins and the tectonic transport of water deep into the Earth. These, in turn, have caused fluctuations in flooding and drought on continents, with periods of extensive shallow seas that enhance biodiversity."
A closer look at the fossil record shows that biodiversity is not constant but fluctuates significantly over tens of millions of years, punctuated by extinction events and the emergence of new species. What was unclear was the driving force behind these changes.
The Earth's crust consists of separate tectonic plates that are constantly moving and recycling. Areas where tectonic plates meet beneath the oceans are known as subduction zones, where water is absorbed deep beneath the mantle and is later expelled through volcanic activity.
Additionally, tectonic movement can cause ocean floor spreading as plates move away from each other. Both mechanisms can lead to changes in sea levels over long periods of time.
The researchers found a 36-million-year cycle in marine biodiversity in their data and simulations, which coincided with a cycle found in tectonic rock data, sea level changes, and broadly over the same timeframe.
These results provide clear evidence that fluctuations in sea level caused by Earth's tectonic cycles play a key role in the formation of biodiversity cycles and the shaping of ecosystems. The researchers state that this may be driven by changes in carbon dioxide levels, but further verification is needed.
