A new study reveals a significant loss of diversity during the Ediacaran Period, which lasted from 635 million to 540 million years ago.
According to a new study conducted by Virginia Tech geobiologists, the cause of the first known mass extinction of animals was decreased global oxygen availability, leading to the loss of a majority of animals present near the end of the Ediacaran Period some 550 million years ago.
The study, led by Scott Evans, a postdoctoral researcher in the Department of Geosciences at the Virginia Tech College of Science, shows the earliest mass extinction of about 80 percent of animals across this interval. “This included the loss of many different types of animals, however those whose body plans and behaviors indicate that they relied on significant amounts of oxygen seem to have been hit particularly hard,” Evans said. “This suggests that the extinction event was environmentally controlled, as are all other mass extinctions in the geologic record.”
Evans’ work was recently published in the journal Proceedings of the National Academy of Sciences. The study was co-authored by Shuhai Xiao, also a professor in the Department of Geosciences, and several researchers led by Mary Droser from the University of California Riverside’s Department of Earth and Planetary Sciences, where Evans earned his master’s degree and Ph.D.
“Environmental changes, such as global warming and deoxygenation events, can lead to massive extinction of animals and profound disruption and reorganization of the ecosystem,” said Xiao, who is an affiliated member of the Global Change Center, part of the Virginia Tech Fralin Life Sciences Institute. “This has been demonstrated repeatedly in the study of Earth’s history, including this work on the first extinction documented in the fossil record. This study thus informs us about the long-term impact of current environmental changes on the biosphere.”
Causes of Decreased Global Oxygen Availability
What exactly caused the drop in global oxygen? That’s still up for debate. “The short answer to how this happened is we don’t really know,” Evans said. “It could be any number and combination of volcanic eruptions, tectonic plate motion, an asteroid impact, etc., but what we see is that the animals that go extinct seem to be responding to decreased global oxygen availability.”
The study by Evans and Xiao is timelier than one would think. In an unconnected study, Virginia Tech scientists recently found that anoxia, the loss of oxygen availability, is affecting the world’s fresh waters. The cause? The warming of waters brought on by climate change and excess pollutant runoff from land use. Warming waters diminish freshwater’s capacity to hold oxygen, while the breakdown of nutrients in runoff by freshwater microbes gobbles up oxygen.
“Our study shows that, as with all other mass extinctions in Earth’s past, this new, first mass extinction of animals was caused by major climate change — another in a long list of cautionary tales demonstrating the dangers of our current climate crisis for animal life,” said Evans, who is an Agouron Institute Geobiology fellow.
Timeline of the Ediacaran Extinction
Some perspective: The Ediacaran Period spanned roughly 96 million years, bookended on either side by the end of the Cryogenian Period — 635 million years ago — and the beginning of the Cambrian Period — 539 million years ago. The extinction event comes just before a significant break in the geologic record, from the Proterozoic Eon to the Phanerozoic Eon.
There are five known mass extinctions that stand out in the history of animals, the “Big Five,” according to Xiao, including the Ordovician-Silurian Extinction (440 million years ago), the late Devonian Extinction (370 million years ago), the Permian-Triassic Extinction (250 million years ago), the Triassic-Jurassic Extinction (200 million years ago), and the Cretaceous-Paleogene Extinction (65 million years ago).
“Mass extinctions are well recognized as significant steps in the evolutionary trajectory of life on this planet,” Evans and team wrote in the study. Whatever the instigating cause of the mass extinction, the result was multiple major shifts in environmental conditions. “Particularly, we find support for decreased global oxygen availability as the mechanism responsible for this extinction. This suggests that abiotic controls have had significant impacts on diversity patterns throughout the more than 570 million-year history of animals on this planet,” the authors wrote.
Extinction’s Role in Animal Evolution
Fossil imprints in rock tell researchers how the creatures that perished in this extinction event would have looked. And they looked, in Evans’ words, “weird.”
“These organisms occur so early in the evolutionary history of animals that in many cases they appear to be experimenting with different ways to build large, sometimes mobile, multicellular bodies,” Evans said. “There are lots of ways to recreate how they look, but the take-home is that before this extinction the fossils we find don’t often fit nicely into the ways we classify animals today. Essentially, this extinction may have helped pave the way for the evolution of animals as we know them.”
The study, like scores of other recent publications, came out of the COVID-19 pandemic. Because Evans, Xiao, and their team couldn’t get access to the field, they decided to put together a global database based mostly on published records to test ideas about changing diversity. “Others had suggested that there might be an extinction at this time, but there was a lot of speculation. So we decided to put together everything we could to try and test those ideas.” Evans said.
Reference: “Environmental drivers of the first major animal extinction across the Ediacaran White Sea-Nama transition” by Scott D. Evans, Chenyi Tu, Adriana Rizzo, Rachel L. Surprenant, Phillip C. Boan, Heather McCandless, Nathan Marshall, Shuhai Xiao and Mary L. Droser, 7 November 2022, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2207475119
Much of the data used in the study was collected by Droser and several graduate students from the University of California Riverside.
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20 Comments
“… the loss of oxygen availability, is affecting the world’s fresh waters. The cause? The warming of waters brought on by climate change and excess pollutant runoff from land use. Warming waters diminish freshwater’s capacity to hold oxygen, …”
Which has greater biological diversity, tropical waters or polar waters?
Without those 5 mass extinction waves, humans wouldn’t be here today. From the population genetics it is like a reset of the gene base. It can accelerate evolution to a new direction through random variables. Process may also lead to loss of the fittest in the ecosystems. This we have seen to happen in earlier extinction waves too. Something to keep in mind why we should stop the 6th mass exticnction wave.
Or why we shouldn’t
Wasn’t the Earth warmer then than now? Am I wrong to assume that C02 emission help plants grow and produces more Oxygen?
I don’t believe the 6th can be stopped, its already well on its way.
Its like the farmers almanac says, you can only keep just so many hogs on one acre.
And we seem hell bent on gobbling up as many of the planets resources as we can wile being totally indifferent to any sustainability issues.
With the government and housing authorities, destroying everything right now. The wildlife is declining, the oxygen we breath is declining, the air is getting more polluted, illnesses are rising, area’s are getting flooded more because of housing, atmosphere is warming because of it all etc etc etc. The list is endless, it’s a domino effect. Personally We are already in an extinction level event.
I so want to read science and absorb the facts. Why do the politics of the left infiltrate all these articles? I wish such articles would begin with their political motives so that I wouldn’t begin reading them and wasting my thought powers on rhe evidence and theories.
Our current environmental concerns are most certainly legitimate. Planetary over-population concerns by homo sapiens as well. Reflect on past (and current) evidence and aspire to a larger perspective. A
> Zack Physicist
Without those 5 mass extinction waves, humans wouldn’t be here today.
I couldn’t agree more! Hopefully we are able to eliminate/minimize the next event. I believe that’s why nature selected for our intelligence. Evolution is exhaustive, it’s got plenty of time
None of this is true. The Bible tells us otherwise. “Science” that disagrees with God is in error. Real science is verifiable and can be duplicated. Short of that is mere speculation. If those that worship at the altar of science were consistent and honest, this would not be presented as anything other than speculation, hypothesis or simply a story..a yarn spun by storytellers.
Yes, climate changes can affect animals and plants. We could have famines if we don’t have enough foods and water.
With humans extinct who will fight climate change?
Anthony..While I respect your beliefs, I find it odd that proof is what you need to believe when it comes to science but not your religion. I Worry There are to many people simply putting their faith in God to solve this problem or simply choosing not to see, that the damage is irreversible.
“Lewis”, science has NO POLITICAL VIEW. Truth is truth, some just don’t understand the difference between fact and opinion. Ignorance and arrogance do NOT change FACTS!!! “Anthony”, religion is not scientific nor can human beliefs change reality. The universe existed for billions of years before humans invented religion/God.
Anthony, prove your god exists… Just fairytales retranslated and intentionally distorted.
Interesting. So what were the oxygen and CO2 levels then? What did those levels drop to?
TO MUCH OXYGEN, PLANTS DIE! Was the water runoff due to fires? Which would burn HOTTER and FASTER in a higher O2 atmosphere. Or was it caused by TO MUCH FOSSIL FUELS BEING USED?
If I remember correctly, wasn’t the Earth “SUPPOSEDLY” ALL OCEAN? NO TO VERY LITTLE LAND MASS! SO MUCH FOR MASSIVE WATER RUN OFF!
RECOMMEND USING SCIENTIFIC ANALYSIS TO COME TO A CONCLUSION, INSTEAD OF POLITICAL AGENDA By YOU and/or the Author or BOTH!
Perhaps the creation of global flood-like waters removed the oxygen from the atmosphere.
This of course will never be considered as it points to the God of the Bible.
You want to believe that such an event won’t happen because it isn’t written in the Bible and God won’t allow it. Haven’t you read Revelations and the warnings there of a world being destroyed? Regardless whether it’s by fire and brimstone or as result of a chain of events resulting from global warning, the fact of the matter is this – nothing is meant to last forever and our time is very short. Denying this and turning a blind eye to science just because it isn’t cannon to the Bible is not wisdom, it is ignorance. We are already facing a mass extinction whether we want to believe in it or not, so if you truly do believe in God with all your hearts you’d better start praying to him now.
The serenity prayer said sincerely and often helped me. Humans have to stop killing each other. The language of love has to become the first lanuage. Watch “Is Genesis History”. It points out the evidence in the earth supports a global rapid change such as a global flood.
Father show us you are the only One true God who was and is. Still to this day in control of all life. We have perversed the words of the living God. Come Lord Jesus the spirit and bride say come. Thank God for his holy one today. If it wasn’t for him all flesh would perish! Because no man do good and are still to this day after their own heart desires. Jesus is the only way to the Father. Read Psalm 53 and repent or Perish. Today is a new day! The former things are past away! I make all things new! In my godliest voice,lift it up for the poor and needy. I speak to all nations tongues and kindreds spirits. Let the Lord be exalted, we have heard of his wrath and others have seen. Thank God he will not give his glory to another. Believe me his words will not return to him void. The wise will be confounded. A child of God will lead us into the future.