By far the worst extinction event earth has ever seen happened just over 251 million years
ago and marked the end of the Permian period.
The end Permian extinction stands out among mass extinctions for its severity.
It was spooky bad, and soundly beats the asteroid that killed the dinosaurs.
It was so bad, it remains the only known mass extinction of insects, which are usually,
at least in general, pretty resilient during other other extinction events.
This extinction hit marine species the hardest, eliminating between 81% and 95 percent of
all marine species.
As far as terrestrial vertebrates, it was 70% and ended the dominion of the amphibians
on earth allowing for the rise of the dinosaurs.
In the oceans, this extinction was the final nail in the coffin for the once ubiquitous
trilobites.
The cause of this calamity was ultimately too much volcanic action by way of the Siberian
Traps, but there may have been contributions of carbon dioxide from the burning of fossil
fuel deposits and increased methane release from earth’s methanogenic bacteria.
Volcanos setting fire to oil and coal fields coupled with methanogenic bacteria eating
the rotting corpses of extinction.
It was the closest this world has ever seen to a true apocalypse.
The release of greenhouse gases from that horrific ongoing process drove the extinction
event.
This extinction was complicated and happened in phases, but the ultimate cause was that
the ocean acidified from absorbing carbon dioxide and also warmed.
This caused a dramatic loss of both oceanic and atmospheric oxygen, and everything that
couldn’t handle the new levels essentially suffocated, or their food did, or their habitat
changed so much that they were simply no longer viable.
This event serves to show that earth’s oxygen level is unusual because it’s being produced
by life itself.
It’s estimated that between 50 and 80 percent of earth’s oxygen is being produced by oceanic
photosynthesis.
If anything goes wrong with that, then the oxygen levels will drop again as they did
during the end permian extinction.
This is expected to happen to earth in the very far future as life on earth grinds to
an end at the hands of the brightening sun.
This great drop in oxygen is ultimately inevitable in about a billion years.
But models show that when it does happen, it will very rapidly drop as far as geologic
time is concerned.
It will only take about 10,000 years for the oxygen to drop to negligible levels.
Of course, if we’re still around and have a billion years of technological advancement
under our belt, this is probably not going to be too much of a problem to deal with.
That’s assuming we’re not a galactic empire by then and haven’t outright forgotten that
we originated on this planet.
But this is also a two way street.
There was also a period where earth had significantly more oxygen in the atmosphere than it does
now.
And if imagining living in a world of hungry dinosaurs chasing you isn’t bad enough,
imagine the world of the carboniferous period.
This period lasted from 360 to 286 million years ago, and was the period just before
the start of the Permian.
It was at this point that earth’s oxygen levels reached their highest percentage, a
whopping 35 percent as opposed to today’s 21 percent.
That amount of free oxygen had a profound effect on the animals of the day.
This period was the age of the amphibians, where species of amphibians grew to enormous
size.
It was really a kind of analogue of the age of dinosaurs, but instead of giant reptiles,
it was giant amphibians.
And that wasn’t the only thing populating the landscape.
There were giant insects as well.
Dragonflies reached enormous sizes with wingspans of several feet.
Flies were the size of mice, and a plethora of new insect species appeared.
This was also the dawn of the great survivor that seems to make it through anything; the
carboniferous saw the dawn of the cockroach.
But they were much larger back then, one fossilized cockroach from this period measures 3 and
a half inches long, or just under 9 centimeters.
This was also an age of unbelievably vast forests.
With forests comes fire, and there is ample evidence in the fossil record that forest
fires were rampant in a 35% oxygen atmosphere.
This is interesting because evidence for fire correlates with earth’s oxygen levels, as
you might expect.
The higher the oxygen, the more wildfires there are.
The lower the oxygen in other periods, and evidence of fire basically disappears.
There is also some debate whether fire works as a regulator of oxygen levels at some point,
and may have been at play in the carboniferous regulating it from getting even higher.
But eventually, something happened during the carboniferous, but before the end permian
extinction, that itself caused a minor extinction event.
This is known as the carboniferous rainforest collapse, where the forests became fragmented
like islands, causing a habitat change that killed off the giant insects.
The cause was again probably climate change brought on by volcanism.
But the real end of this period was the end permian extinction and the drop in oxygen.
Earth’s oxygen levels for most of its history were almost non-existent to very low.
Only when photosynthesis evolved did it start to oxygenate, but the oxygenation of earth’s
atmosphere was a very long and slow process.
Once high oxygen levels and the evolution of complex life was achieved, Earth’s atmospheric
oxygen levels then varied widely at different periods.
But there is somewhat of a mystery here.
About 55 million years ago, earth’s oxygen levels reached some type of equilibrium that
it’s more or less maintained tightly ever since.
That’s not really out of line with previous periods, but the specific reason for this
period of stability is not fully understood.
But there’s an even bigger mystery here.
Cue the spooky october music, and here we go.
This period of stability seems to have altered about 800,000 years ago and earth’s oxygen
levels are dropping.
Based on analysis of bubbles preserved in arctic and antarctic ice, in that period we’ve
lost .7 percent of earth’s oxygen.
You can’t blame the start of this on us, anatomically modern humans didn’t appear
until 200,000 years ago, well after this started.
Nor can you blame it on predecessor hominids, they just didn’t have the numbers.
Whatever is causing the decline is something earth itself is doing, as in past rises and
drops in oxygen levels.
Remember, it could be said that the end permian extinction was the earth itself causing a
reset.
The best hypothesis so far is that there has been an alteration in erosion rates.
Geology can lock oxygen up and higher rates of weathering can result in variations of
how geology reacts with oxygen.
This may have been due to the rapid oscillations of glaciation and interglacial periods that
have marked earth’s last million year history.
Another is that there has been a 56 million year trend of cooling overall allowing the
earth’s oceans to hold more oxygen.
This is an effect you can experiment with, a can of your carbonated beverage of choice
when opened will go flat faster if it’s warm than if it’s refrigerated.
Or it could be due to something we haven’t thought of, and that trend could continue.
And we can always aggravate it with our emissions, and oxygen use by burning fossil fuels sequestering
oxygen from the atmosphere.
We already see ocean acidification occurring, and we’re most likely causing it with our
carbon dioxide production.
But if there is some process going on with earth that has nothing to do with our activities,
this could get really unpredictable leading conceivably to oceanic photosynthesis taking
a hit and earth’s oxygen levels dropping at a higher rate.
This would be catastrophic for us.
We are one of the most vulnerable species on earth to dropping oxygen levels.
Our giant, complex brains need oxygen or they stop working.
I’ve seen this personally.
I once experienced something called vasovagal syncope, commonly known as fainting.
It was due to a medication I briefly had to take and when it hit, I had about one second
of partial consciousness as I leaned on a door frame, closed my eyes and then total
blackness, or lack of anything really, until I was on the ground and horizontal and blood
pressure and oxygen was restored to my brain.
I then promptly found out that I had face planted onto a set mousetrap, set it off with
my eye thankfully with no damage, and ended up with a mouse-trap arm shaped bruise on
my forehead.
This on a day when I was set to have dinner with my parents and siblings and an aunt and
uncle or two.
Needless to say, everyone noticed, and I had to explain it.
Now that I’ve told the world that, I digress.
We don’t last long without 21 percent oxygen levels, at least in a functional state.
It’s estimated that we could handle only a relatively small drop in oxygen levels before
going extinct very rapidly, perhaps as little as a few days if it happens quickly.
This extinction number is 19.5 percent, we can’t go below it.
If it continues to drop after we’re gone, even the venerable cockroach goes extinct
at 12 percent.
But we are also a technological species and can think of technologies to mitigate this,
but it leads to a rather dystopian view of the future.
We could found a Mars colony even now, and even an earth with dropping atmospheric oxygen
levels still has enormous amounts of oxygen locked up in the water.
As our world returns to the anaerobic bacteria, earth’s first life would inherit it again,
we would have to treat earth much like we would Mars during colonization.
We would have to build things like domed cities and habitats to grow our food and become a
kind of ark civilization waiting it out in artificial environments until we could reestablish
plants and terraform earth back to what it was.
And drops in oxygen levels of this planet aren’t likely to be fast, rather they are
more likely to be gradual, with plenty of warning to set all of that up.
But it would be a strange period indeed, reminiscent of science fiction books like Hugh Howey’s
Wool series or even the movie Interstellar where earth simply becomes unviable for us,
and it may even do so through means we didn’t cause, rather earth itself did.
And that leads to alien scenarios.
It has been suggested that climate change might be a universal trait among all civilizations
in the galaxy.
Everyone goes through a fossil fuel era and then either transition to something else,
such as fusion based energy production, or they either go extinct or head out into space.
This could lead to odd scenarios where civilizations exist in star systems that have no habitable
planets.
What if the first civilization we detect in the galaxy clearly has made some very bad
decisions?
Would we learn from that?
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently musing about all
the great food we’ve lost.
It’s estimated that 99 percent of all species that have ever existed have gone extinct.
There are species on this world like the avocado that actually may have gone extinct without
our intervention.
I think we’ve missed out on a whole lot of good food and imagine how tasty the trilobites
were with butter sauce and be sure to check out my books at your favorite online book
retailer and subscribe to my channels for regular, in-depth explorations into the interesting,
weird and unknown aspects of this amazing universe in which we live.