By now, it’s common belief that the demise of the dinos and other species is attributable to catastrophic events (think: crashing asteroids, sky-darkening volcanoes and mass epidemics).
But here’s one theory that takes all the others out with the tide: Change in sea level is the real culprit.
“The expansions and contractions of those environments have pretty profound effects on life on Earth,” says Shanan Peters, a University of Wisconsin-Madison assistant professor and author of the study that explored this new theory.
In particular, it is the ebbs and flows of water and sediment over geologic time that has led to mass extinctions over the past 500 million years. According to Peters, it’s also this change that determines the composition of life in the oceans.
A brief history of mass extinction events
Scientists believe that there may have been as many as 23 mass extinction events since life first began on Earth 3.5 billion years ago. Included in these are the dinosaurs, but also much simpler life forms, such as single-celled micro-organisms.
Consider this: in only the last 540 million-years, there have been five well-documented mass extinctions. Here, marine plants and animals were the major casualties, with as much as 75 to 95 per cent of such species dying-off.
A modern problem
One reason for these shifting tides is that, over hundreds of millions of years, the world’s oceans have responded to the shifting of the Earth’s tectonic plates and to changes in climate.
Experts are quick to point that our own species will bear witness to a rapid change in sea level.
“This breakthrough speaks loudly to the future impending modern shelf extinction due to climate change on Earth,” says Rich Lane, the National Science Foundation (NSF) Program Manager.
Not the only factor
Peters argues, however that while the changing sea level theory doesn’t preclude possible contributors to mass extinctions, it does provide a common link among these events over a significant stretch of the planet’s history.
“The major mass extinctions tend to be treated in isolation by scientists,” Peters says. “This work links them and smaller events…and it also tells us something about who survives and who doesn’t across these boundaries. These results argue for a substantial fraction of change in extinction rates being controlled by just one environmental parameter.”
The study appears in the June 15 edition of the journal Nature.
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