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University of Michigan Museum of Paleontology
The ocean in Devonian times: Is the past prologue when it comes to biodiversity collapse?
A long, long time ago — between 378 million and 375 million years ago — about half of all species on the planet vanished. The trigger for this mass extinction, one of five known in Earth's history, was a lethal combination of sea level rise and invasive species, according to a new study.
"The basic processes that normally result in new species forming were blocked," study author Alycia Stigall, a paleobiologist at Ohio University, told me today.
In normal times, species are always going extinct, but as they die off, new species arise. That keeps the planet's number of species relatively constant. "When you take some species away but don't replace them, the overall result is a collapse in global biodiversity," she said.
The findings suggest that the planet's current ecosystems, which are experiencing loss of biodiversity, could meet a similar fate.
How species rise and fall
One path to the rise of new species starts when a population is split in half due to a geological event, such as the rise of a mountain chain that prevents the two halves of the population from interbreeding. Over time, the two groups develop into new species.
During the Late Devonian period that Stigall studied, most of Earth's creatures lived in shallow sea basins. As sea levels rose due to warming temperatures and shifting land masses, these basins were connected — that is, the barriers that kept them separate disappeared. New species stopped forming.
"The Devonian has normal extinction rates," Stigall noted. In other words, the number of species dying off wasn't abnormally high, as it was when a space rock slammed into Mexico's Yucatan Peninsula and killed off the dinosaurs about 65 million years ago. "So it is really the stopping of speciation that results in a major collapse.
"The other thing that happens when you raise sea level is some species move into that basin that didn't previously live there, and that's the invasive species," she added.
Some of these invasive species fail to carve out a niche for themselves and die off, but others — typically generalists that can eat almost anything and survive in a range of environments — outcompete the natives. "They basically take over and stop the ability of new species from forming," Stigall said.
Lessons for today
Many scientists say that we are in the throes of a sixth great mass-extinction event. The two main reasons are habitat loss — land converted to human use is less available to other critters — and the fact that we are moving species around the planet.
"What we can expect in the long term is that because we have this global movement of invasions, we can expect speciation rates to be very low, but we also know that because of habitat loss, the extinction rate is very high. So we are really looking at a very bad combined effect," Stigall said.
Knowing this, conservationists may be smartest to focus their efforts on generalist-type native species, she added.
"Things that are very narrowly adapted, specialist species, are unlikely to survive. They are unlikely to speciate in the future, and they are also unlikely to survive the habitat loss," she said. "So things like polar bears that are really cute — there's just not much we are going to be able to do for them."
Stigall's findings were published today in the journal PLoS ONE.
More stories about mass extinctions:
- Earth's Timeline: Where does the Devonian era fit in?
- Scientists: Haiti's wildlife faces mass extinction
- Is algae secret ingredient in mass extinctions?
- Mass extinctions may follow one-two punch
- Study sees mass extinction via warming
- Did Great Salt Lakes trigger mass extinction?
- Meteors not only culprit in mass extinction
- Mass extinction threat: Earth on verge of huge reset button?
John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).
Leave a Comment:
yea, focus on the generalists. That's us. We eat almost anything and survive in a range of environments.
"What we can expect in the long term is that because we have this global movement of invasions, we can expect speciation rates to be very low, but we also know that because of habitat loss, the extinction rate is very high. So we are really looking at a very bad combined effect,"
Excellent summary of the current state of affairs. Unfortunately, there is probably little that we can do to change it. We are likely to be in a biodiversity collape that is unprecedented in Earth's history.
No, no we aren't. There are periods in Earth's history when 95% of all species died off, including almost all large animals and plants. We're still nowhere's near that kind of event.
Also, this article fails to take into account the impact of our travel through the galaxy. Every ~68 million years or so, our solar system peaks out of the northern end of the galactic disk. This results in exposure to massively more cosmic radiation, as we are no longer shielded from the very active core by nebuli and other star systems. This radiation peak results in significant loss of biodiversity and was likely the groundwork for both this extinction and the dinosaur extinction 65 million years ago. Since we're still a few million years off from the next dose, odds are low that human impacts will still be a destructive force on the ecosystem when it comes. It'll either be resolved, or already destroyed.
There's something specious about this whole argument.
I see twitter as an invasive species........
environmentalism beware.....environmentalists want advocates.......mindless voices will kill off the real purpose of knowing ones own environ......let us establish a premise the computer screen is sterile......and we decide if the truth is revealed.....
do not get me wrong "corn belt"......I love the studies of science and mathmatics.....a damn genius they call me....DNA and genetics is my latest love....hold it to the ground and see if we survive our own folly....
Ephesians 5:6
Geniuses also tend to see relevancies in the articles they read, which your post, and overall point, have nothing to do with.
A genius you are not.
Is a reduction in the number of species actually a problem? One could argue that a reduction in the total biomass would be a bad thing, but not a reduction in the number of species.
From a human perspective, the current reduction in diversity can be a problem, because it puts our sources of food at risk from single diseases. In addition, invasive species can cause problems with species that are food sources by displacing them. A more efficence species may produce less food for us.
A reduction in the number of species means a reduction in the variability in the world. This means that the remaining species will be less able to quickly adjust to change, as the odds that a specialized species who can handle the new environ drops. A drop in the number of species is very bad, indeed.
We need a virus that sterilizes humans. That would save the planets diversity.
You can always start with yourself...snip snip.
Frankly, the guy has a bit of a point. The US congratulates parents who have seven kids, even those who cannot afford them. And the amazing thing is - we help support them!
When I heard that tigers were breeding less due to roads they won't cross to find mates, I thought they might be one of the species that won't be with us much longer. They don't breed well in captivity. Adaptation is the key to species perpetuation in an ever-changing world.
The Devonian was the Age of Fishes. Amphibians, reptiles, birds, mammals, all would come later. Maybe the rising seas, then again fell, and stranded pockets of fishes which developed fins, or breathing apparatus to survive on land. You have to remember that at one time, no plants were living on land. Nor insects. Rising seas, or fallling seas, certainly will have consequences, but I'm not sure there is someone who determines which forms of life are good, or bad, other than personal bias as to what works best in their private gardens.
Like the Lord High Executioner in Gilbert & Sullivan's Mikado, I have my list...of species that would not be missed. The fire ant, for starters, and all disease-carrying mosquitoes. Jimmy Carter doesn't like the Guinea Worm.
And then there are those who hate Humanity, (except for themselves, of course)...
AH--now I've got it !
The sky isn't falling, its the sea that's rising !
It really is. We're only about 10,000 years out of the fourth ice age in a million year-long cycle. Of course sea levels are rising and the planet is warming, as it should be.
Attaching any human responsibility to these truly massive events is presumptuous at best. There is a lot of inertia in the system. Think in 100,000 year-long intervals to get a better perspective.
The temperatures coming out of the ice age peaked about 8,000 years ago and we have been varying slightly beneath that level ever since. The current trends have nothing to do with ice age cycles.
It would seem presumptuous that humans could affect for the climate, if it weren't for the scientific fact that we can.
That's disputable, Jock, and far from scientific "fact." Leading environmental scientists strongly believe that mankind's use of fossil fuels and other chemicals is causing the warming trend, but there are some hold outs who suggest that a number of other factors may be at play instead (such as the increased solar activity we've seen of late).
Not trying to start a war of text, just stating that the final word on the subject has not been spoken.
I saw this article recently and thought it may add something to the climate discussion:
http://www.nasa.gov/topics/solarsystem/features/solarcycle-sorce.html
Turns out, solar cycles are more complex than we thought. Gee, who knew?
Impacts like Chixulub (the "space rock" mentioned) are the sort of thing we need to focus on more than the obvious consequences of our emergence as a species which can "eat almost anything and survive in a broad range of environments". One event going unmentioned is a similar impact at the end of the Permian. It's appropriately referred to as "The Great Dying"- because not merely half, but about 99% of the species alive at that time died off (geologically speaking) overnight. Asteroidal impacts release energies exceeding those of any fusion weapon ever built.
This article could have been summed up as: "We are outcompeting a lot of other animals and spreading other generalists like rats as we do so. We have largely extinguished our natural predators in the process. This destroys biodiversity and reduces the total number of species worldwide- and will continue to do so until our population peaks, civilization collapses, and we die back to sustainable levels." Or, as Robin Williams once said: "Reality: what a concept".
Fission, not fusion. :)
Hydrogen bombs use a reflective concentration of neutrons released by a fission trigger to focus energy sufficient to start a fusion reaction in deuterium or tritium under great pressure- I'm being deliberatley vague, though better information is widely available. I said fusion- I meant fusion. No doomsday device (I know of) has ever been built which could equal the damage of an asteroid strike like Chicxulub- you're talking about a wall of fire encompassing half the planet, with ejecta the size of city blocks splashing back out of the atmosphere and orbiting half the planet to land on the other side. The nuclear winter effect is still suspect- tropical bees would not have survived the drop in temperature they postulated originally- yet, there they are. The dust would have caused a catastrophic winnowing of advanced species- and administered the coupe de grace to dinosaurs- which may already have been fading for other reasons (long topic).The one off Australia was much larger.
So when was a "fusion weapon" developed and by whom?
" When all the plants die the earth will die.When all the animals die the earth will die.When all the humans die the earth will flourish". Russell Means. Humans are the species that destroy their own support base.
Well Tom-355574, you have clearly outlined the co-dependency of plants and animals on earth. Problem with your logic is you could replace "humans" with pigs or lemmings or any other animal (because humans are a type of animal, and it would read just as true. Also, you could replace that last sentence with a type of plant and would still work. So other than plants and animals need each other what is your point?
"One path to the rise of new species starts when a population is split in half due to a geological event, such as the rise of a mountain chain that prevents the two halves of the population from interbreeding. Over time, the two groups develop into new species." "1) collect socks 2) . . . 3) make gold" Nice science there. Over time they will develop into new genuses, we know a certain gene pool must exist or a species will go extinct, therefore Darwinian evolution cannot create new species. They are doomed to extinction the moment they emerge.
So, your argument is that change is impossible because the moment a new species emerges it dies? I don't follow your logic... Your argument would, for example, be news to the Swine Flu, which rapidly evolved inside pigs, merging two disparate flu strains into a new flu strain-- and last I checked, it's still around and pounding the bejeezuz out of Europe.
Let me give you another example: Wolves. Now, we know that man domesticated wolves some 20,000 years ago. In that time, we have, by selective breeding and geological spacing, have made, from wolves, such ridiculous canines as chihuahuas, dachshunds, teacup poodles and, on the opposite spectrum, bull mastiffs. And that was in just 20,000 years. Now imagine the same process extended over millions of years and you start to get the picture. There were never any "poodles of the Serengeti" (with respect to Larson) or wild dachshunds roaming prehistoric badger haunts. We made those animals by controlling the conditions under which they bred. Nature, too, by chance mostly, controls the conditions by which the animals on this planet breed, enforcing change. Over a long enough time line, that change results in distinct species.
Your example of gene pools is also inaccurate. Chimpanzees share 98% of the same genetic information as humans, yet they are a distinct, successful species in their own right. They certainly haven't seized up in a collective death throe as you have suggested they should have.
Learned my lesson! I will never move to Devonia.
BUGS!!!
The next big thing....they are the top generalists, really, not us. My money is on the bugs after we are gone...oh, wait I won't be able to collect...Oh, well...
Oh well, ya gotta go sometime. I'm just hoping that all the other humans go extinct before me.
mans been getting wiped out for 10000 of years maybe more ...it would be good for this over populated world to go thought another mass extintion
We are the "invasive species" currently causing mass die offs. We have invaded every nook and corner of the world, out competing in every other creature's living space.