Stories tagged extinction
Cumulative impact by humans on the oceanCourtesy National Center for Ecological Analysis and SynthesisOne of the great extinctions in Earth history occurred 252 million years ago when about 95 percent of all marine species went extinct. The cause or causes of the Great Dying have long been a subject of much scientific interest.
Now careful analyses of fossils by scientists at Stanford and the University of California, Santa Crux offer evidence that marine animals throughout the ocean died from a combination of factors – a lack of dissolved oxygen, increased ocean acidity and higher water temperatures. What happened to so dramatically stress marine life everywhere?
Geochemical and fossil evidence points to a dramatic rise in the concentration of carbon dioxide in the atmosphere, which in caused a rapid warming of the planet and resulted in large amounts of carbon dioxide dissolving into the ocean and reacting with water to produce carbonic acid, increasing ocean acidity. The top candidate for all this carbon dioxide? – huge volcanic eruptions over thousands of years in what is now northern Russia.
Why should the Great Dying be of more than just academic interest? Humans currently release far more carbon dioxide into the atmosphere than volcanoes and we are releasing carbon dioxide into the atmosphere at a rate that greatly exceeds that believed to have occurred 252 million years ago. The future of Earth’s oceans will be determined by human decision making, either by default or by design. What do we want our future ocean to be?
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Is the end near for Homo sapiens?Courtesy mars_discovery_districtWell, there certainly seems to be a lot of doom and gloom in the news these days: climate change, killer asteroids, End of the World prophesies, rogue states building nuclear weapons. It's enough to make a grown man burst into tears. There have been some bright spots in the future, though. The End of the World predicted by the Mayan calendar for next December seems to have already passed without a problem. Since the Mayans forgot to include Leap Year in their forecast, the deadline actually came and went about 7 months ago without much ado.
But what about all the other looming events? Those could still happen, couldn't they? I mean what's the point of getting out of bed if you're just going to get wiped out by the super volcano that's smoldering under Yellowstone National Park? I suppose that could actually happen. But, you know, even if it does, according to this video at New Scientist, it probably wouldn't mean all of humankind would go extinct. Just a lot of us. I'm sure you feel better now.
Javan rhinocerosCourtesy Public domain (via Wikipedia)Poised on the edge of extinction, some rarely-seen Javan rhinoceroses (Rhinoceros sondaicus sondaicus) have been captured - on motion-triggered video cameras - at the Ujung Kulon National Park on Indonesia's island of Java. Park officials and the World Wildlife Fund recorded four of the ungulates, a number that amounts to about 10 percent of the species living population. NPR has the story and some of the video and pictures here.
LINKS
Some Javan Rhino Info
If it had hands: it would be holding your life in them. Just saying.Courtesy splorpGather ‘round, Buzzketeers, so that I might tell you all a story.
“What story,” you ask?
Is it the one about the little blond girl who is killed by bears for breaking and entering? No, not that story.
Is it the one about the boy who killed an acromegalic man by cutting down the tree that held his fort? No, it’s not that story either.
Could it be the story about the little Blood member who couldn’t tell the difference between a wolf and her own grandmother, and was subsequently devoured by that very wolf? Oh, I wish it were, but it’s not that story.
No, the story I have for you all is even more enduring and horrifying than all of those. It is the story of biodiversity, and how it will freaking destroy you if you mess with it.
Sure, snort dismissively if you must, but you’ll soon be singing a different tune. A sad tune about how everything you ever knew and loved has been taken away from you.
“But how can a concept—and a boring concept like “biodiversity”—hurt me?” Ah, see, but what you don’t know can hurt you. You’re like the little blond girl, screwing around in a house that belongs to bears. She might not have known that it was a bear house (although it’s hard to imagine that she could have missed all the signs), and yet she was destroyed. So listen up.
You see, all biodiversity is is the degree of variation of living things in an ecosystem. Lots of biodiversity in an ecosystem, lots of different things living there. Little biodiversity in an ecosystem, few species living there. And biodiversity includes all forms of life, from your vampire bats and hagfish, to your streptococcus and your slime molds.
At the moment, biodiversity on the planet is on its way down. Lots of the things we do these days make life harder for other species, until there are very few or none of them left. And, sure, no one wants to see a panda get hit by a train, or watch an eagle being run over by road grading equipment, but who cares about the smaller, grosser stuff, like algae or germy things? We could probably do with a few less of those, right? Right?
Wrong, Goldilocks! An attitude like that is bound to get you turned into bear meat.
And here’s where my story begins (again)…
Once upon a time, long, long ago, everything died.
Well, not everything-everything, but pretty well near everything. It was called “the Permian extinction” (we’ve talked about it on Buzz before: here), and more than 90% of all marine (water) species and 70% of all terrestrial (land) species on the planet went extinct. It was way worse than the extinction that would eventually kill off the dinosaurs, and it took the planet a lot longer to recover from the Permian extinction.
What caused the Permian extinction? Oh, you know, a lot of stuff. Probably a lot of stuff. See, while we can more or less say that the dinosaurs were killed off by a giant space rock, it’s harder to say what did in the creatures of the Permian period. After all, the Permian ended almost two hundred million years before the extinction of the dinosaurs. But people have plenty of good guesses: maybe a few smaller space rocks hit the planet, maybe massive volcanic eruptions in what would become Asia kicked dust and poisonous gas into the atmosphere, maybe the oceans suddenly released massive amounts of methane… probably it was a combination of these things and more, and the extinction probably happened in waves before the planet became a good place to live again.
But here’s another straw for that dead camel’s back: the algae died. Not all of it, but lots and lots of the algae died. But why, and why did it matter? After all, it’s just algae.
Scientists aren’t sure exactly what cause so much alga—microscopic plant-like ocean life that turns sunlight into food—to die, but it looks like a sudden rise in the levels of sulfur in the oceans might have had something to do with it. It could be that there was an explosion in the population of sulfur using, hydrogen-sulfide releasing bacteria in the oceans, which would poison the algae.
In any case, there was a large die off of the sort of species we don’t give a lot of thought to. And what happened? The bear meat hit the fan!
Because they turn so much sunlight into so much food, algae act as the basis for most marine food chains. When the algae were gone, photosynthetic bacteria took its place to some extent, but the bacteria were a poor substitute, and the oceans were left with much, much less food. Also, algae produce a significant amount of the planet’s oxygen, and their absence would have created atmospheric changes as well.
This alone might have been enough to cause extinctions, and combined with the other natural calamities of the end of the Permian, it’s no wonder there was such a massive extinction event.
What a good story, eh? Now, if someone asks you what’s so great about biodiversity among the slimier and more boring species, you can just repeat this post, word for word. Or you can repeat this, the short version, word for word: “Because, Mom, if the algae die, we’ll be left choking and crying among the ruins of humanity for the rest of our short lives. And happy birthday.”
T-rex could run, but he couldn't hide: More than one asteroid impact may have wiped out non-avian dinosaurs.Courtesy Mark RyanThe meteor that created the Chicxulub Crater in Mexico's Yucatan Peninsula may have not been the only one responsible for the extinction of non-avian dinosaurs 65 million years ago. "Fern spike" evidence in another similarly-aged crater found in the Ukraine indicates at least two large impacts took place within a few thousand years of each other. Concentrations of fern spores are commonly found in the mud that fills in impact craters. The Boltysh Crater contains two layers of spores within three feet of each other, indicating not one but two impacts.
"We interpret this second layer as the aftermath of the Chicxulub impact", said Simon Kelley, co-author of the study, and professor of Isotope Geochemistry at the Open University.
Both the Chicxulub and Boltysh bolide events could have been part of a meteor shower that hit Earth at the end of the Cretaceous. The study appears in the journal Geology.
SOURCE and INFO LINKS
BBC story
The K-T Extinction event
Another sad day for wildlife lovers as yet another one of the world’s beautiful creatures is declared extinct. The Alaotra grebe from Madagascar was added to a growing list of modern day extinctions of bird species, nearly 190 total out of the 10,000 bird species remaining in the world. I shudder to think how the threatened and endangered list will change with this terrible oil spill in the gulf.
Proof of extinction: The fossil remains of Knightia, an extinct Eocene fish found in the Green River Formation.Courtesy Mark RyanOver at Smithsonian.com, Sarah Zielinski writes that when the concept of extinction first came into the public consciousness some 300 years ago, it caused much the same controversy as evolution does today. But she views extinction’s undeniable acceptance now as a hopeful sign that evolution will someday enjoy the same.
Dino killerCourtesy Donald Davis (for NASA)
How Earth impact kills dinos
As "mdr" explained recently in, astroid found guilty of killing dinosaurs that a panel of scientists, after reviewing all evidence, blame an asteroid impact for the demise of the dinosaurs.
Ozone killed the dinosaurs
A paper has just been published saying that dinosaurs choked on ozone.
A new study in the journal Paleogeography, Paleoclimatology, Paleoecology puts forth the idea that the Chicxulub impact, long blamed for the extinction of the dinosaurs at the end of the Cretaceous era 65 million years ago, could have done them in by flinging huge amounts of ozone precursor chemicals -- nitrogen oxides, methane, and other hydrocarbons -- into the air.
Below the article in Discovery News, this comment by 1sang (Doug) explains why mammals and avians survived.
In order to (survive) all you'd have to do is get on steeper slopes and find enough food to live for a couple of years. Mammals and smaller avian dinosaurs could more easily accomplish this than their massive cousins (in fact, many were probably already in this safety zone away from the many large predators roaming the lowlands).
He also notes that methane release leads to an increase in ozone and that today we have the beginnings of lots of methane being released (I wrote about this here: Methane ice).
What sent the dinosaurs packing?: The number one suspect, a gigantic asteroid, has finally been convicted of the crime.Courtesy Mark RyanAfter studying all available evidence and listening to alternative theories (and despite no eyewitnesses), a panel of 45 international scientists has decided it was a huge asteroid that killed all the non-avian dinosaurs some 65 million years ago.
The asteroid, described as a 7 mile-in-diameter chunk of space rock, has been the prime suspect in the ruling reptile’s demise ever since scientists Luis Alvarez and his son Walter first identified a one-inch layer of iridium in Late Cretaceous-age rock exposures throughout the world. The layer was located exactly at the point in the rock record where the Cretaceous period ended, and the Tertiary period began (K-T boundary). 
Smoking gun for dinosaurs' demise: K-T Boundary with 1-inch iridium layer (arrow) exposed 10 miles west of Trinidad, Colorado. The element iridium is very rare on Earth but concentrated in meteors and comets. The same iridium layer is found in several exposures around the world, and corresponds in age with the Chicxulub meteor crater in Mexico's Yucatan Peninsula. The layer marks the end of the Cretaceous era, and no non-avian dinosaur remains have ever been found above the boundary. The coal layers above and below the iridium suggests a swampy environment when the layer was laid down in this area of Colorado.Courtesy Mark RyanThey predicted a meteor impact crater of the same age would be found as the source of the iridium since the element is rare on Earth but common in outer space. Then in 1990 their predictions were verified when the Chicxulub impact crater was discovered in Mexico.
Although the impact site was mostly submerged off the north coast of the Yucatan Peninsula, samples taken from it dated to the end of the Cretaceous period. This and other corroborating evidence helped bolster the killer asteroid hypothesis as the primary theory for the extinction event that wiped out 70-75 percent of life on Earth including non-avian dinosaurs, and other large reptiles. The asteroid is estimated to have slammed into Earth traveling 10 times faster than a rifle bullet, and released the energy of a billion atomic bombs. The impact instantly vaporized a large area of terrain, and sent an explosion of dust and rocky debris up into space, much of which fell back into the atmosphere in a fiery rain. It left a crater 110 miles across, and a cloud of dust circling the planet for weeks. The diminished sunlight would have disrupted the environment severely, including the food chain. Mammals and other smaller creatures were able to survive across the boundary and flourish in later periods.
But not everyone was convinced by the evidence. Other causes for the mass extinction, such as extreme volcanism in India, falling sea levels, disease epidemics, and even fungal infection were all tossed around as possible culprits.
But in the end it seems the evidence implicating the asteroid in the K-T* extinction event was just too strong, and after much deliberation, the impact has been determined as the official cause of death. The panel published its decision in the latest issue of Science.
*“K-T” stands for Cretaceous-Tertiary, however, use of the term Tertiary is being discouraged now, and the time span it occupied has been replaced with the Paleogene and Neogene periods. So a more proper, up-to-date term would be Cretaceous-Paleogene or K-Pg extinction event.
LINKS AND SOURCES
More about dinosaur extinction
BBC story
Impact theory counterview
Georges CuvierCourtesy Public domain via Wikipedia Commons
Born August 23, 1769, naturalist Georges Cuvier was one of the most influential scientists of the late 18th and early 19th centuries, and helped establish the fields of comparative anatomy and vertebrate paleontology. One of his most important contributions to science was establishing that species extinction was a fact. You can read more about him here. Cuvier died in 1832.
