The Earth Story

Extinction of the Dodo Bird

The dodo bird (Raphus cucullatus) was a large flightless bird from Mauritius (a small isolated island just east of Madagascar). It averaged at around 3 feet tall and 22-40 lbs. The dodo bird was last seen in 1662.

Prior to the introduction of non-native species by humans, dodos had no natural predators on Mauritius, and therefore evolved to become large-bodied, relatively latent in their mobility, and pretty much fearless of larger animals. Humans arrived on Mauritius in 1598. The introduction of the European's cats, rats, pigs, dogs, etc. quickly led to not only their demise, but also the destruction of the dodos' nests, and the killing of their young and eggs. One of the first explorers of Mauritius also described the dodo bird as being extremely delicious, and large enough to feed two people.

From human arrival in 1598, it only took 60 years to demolish the dodo species. Researchers are now looking into possibly using cloning as a method of bringing the dodo back to life, which may cure the long-lived curiosity everyone has on what the dodo ate (provided that feeding behaviour is an instinctual trait, not a learned trait), how it would mate, and what it really looked like (you can watch a video on the dispute of the dodo's actual morphology here:http://bit.ly/1G8dNZK ).

~Rosie

Image: http://bit.ly/1CRMvU7

References: http://dodobird.net/

http://ind.pn/1HIfrU3

http://bit.ly/1ItvaVe

The Glyptodon

Armadillos are a common sight in the southern United States…. except that most of the time they are dead and on the side of the road. After living in Texas most of my life, I saw my first LIVE armadillo recently and it seems like a moment to celebrate.

It certainly was an exciting wildlife encounter, but during the Pleistocene, there was an even more bizarre armored creature tramping through this region—the glyptodon, which was very similar to an armadillo, except huge. Like size-of-a-small-car huge. This mammal is often compared (in size and appearance) to a Volkswagen Beetle.

The glyptodon (and its cousins) had an armored shell that was very effective protection—even the fiercest carnivores had trouble sinking their teeth into it. There does seem to be one predator, however, that might have found a way around (or through) the hard shell—humans. The extinction of the glyptodon in South America 10,000 years ago correlates with the arrival of humans.

Why would humans hunt the glyptodon? For one, they provided a lot of meat. But also, the armored shell might have had some appeal—evidence suggests that humans used glyptodon armor as shelter and may have lived inside it.

-CM

For more information: http://wrd.cm/1DNNmoE http://bit.ly/1w3YlwC

Photo Credit: Arent http://bit.ly/17RhYg5

The PETM – Why It Feels Like Deja Vu

The Palaeocene Eocene Thermal Maximum was an event that took place 56 million years ago at the end of the Palaeocene and lasted for 150,000 – 200,000 years. The average global temperature rose by 5-9°C (9-16°F) leading to mass migrations and extinctions of flora and fauna.

The event was discovered when marine sediment cores from Antarctica showed a large and sudden excursion ( a sharp spike in the values) in carbon isotopes, indicating that a large amount of CO2 had been rapidly expelled into the atmosphere. Sounds familiar doesn’t it?

Further evidence of a large expulsion of CO2 is shown within marine sediment cores. As you can see, there is an abrupt change from white to red, indicating a rapid dissolution of calcium carbonate (white mud) that only recovers after the event (the red clay). (Increases in CO2 dissolved within seawater lead to calcium carbonate dissolving and eroded terrestrial clays (red) are deposited instead).

Today global temperatures are increasing at rate that far exceeds that of the PETM; a warming of 1°C per 100 years compared to 0.025°C in the Palaeocene.

While current global temperatures are far lower than those during the PETM it is the speed of the change that matters. All life forms take time to adapt and evolve, and it is the rapidity with which the world is warming that is threatening life as we know it. Humans are not immune to this change, and it is very likely that the current warming could lead to the next mass extinction if it is not curtailed.

Climate change is still a topic of hot debate but the most important fact to remember is this: No matter what happens the Earth will still exist and life will find a way to go on. The Earth has survived global glacials as well as global deserts and has feedback cycles that always return it to a habitable state. However, these climate shifts always incur casualties, and if there is another mass extinction, there is no guarantee that the human race will survive to tell the tale. There is no doubt that humans are expelling large volumes of CO2 into the atmosphere and therefore control over the future really does lie in our hands.

Reference: https://www.e-education.psu.edu/earth103/node/639

Further Reading: http://www.wunderground.com/climate/PETM.asp?MR=1 http://www.skepticalscience.com/co2-rising-ten-times-faster-than-petm-extinction.html http://www.geol.umd.edu/~jmerck/geol100/lectures/36b.html Image Credit: University of California Santa Cruz - Earth and Planetary Sciences

Protect our Species

The title of this post is the theme for today, April 22nd 2019, the 49th annual “Earth Day” event. This theme was chosen to recognize the fact that, through human activities, this planet is currently experiencing a rapid drop in biodiversity – one comparable to the largest events in the geologic record – and these changes pose major challenges for humanity as a whole.

The Geologic record is a part of the tale of this theme, as the geologic record tells us how species have changed over the history of this planet. 550 million years ago, give or take, a group of organisms figured out how to produce hard parts – shells and other features that could be adapted for defense, attack, or structure – and they revolutionized life on Earth. Many organisms that existed before this event doubtless went extinct, but because they didn’t make hard parts we have very sparse records of them.

Since that time, there have been 5 times recorded in the fossil record where more than 75% of species on Earth went extinct: these are commonly nicknamed the “Big 5” mass extinctions. Some authors may count more by splitting these extinctions into separate events, as in the Cambrian, but each of them shows as a spike in extinction rate on this plot. The causes of these extinctions have included the impact of an asteroid, huge volcanic eruptions, and major climate shifts, but regardless of their cause they have each left their mark on this planet. Some of them removed species such as the non-avian dinosaurs that allowed mammals and birds to flourish, others such as the end-Permian caused compete changes in the types of organisms that dominated the oceans.

While these extinctions may have happened long ago, they are relevant to what we are seeing on the Earth today, due to changes driven by humans. The best estimates suggest that over the last few millennia as human civilization and population has grown, thousands of species have gone extinct already. An estimate published a few years ago suggested that over the last thousand years, the rate of extinction amongst vertebrate species right now is more than 100x the natural rate of extinctions that would be occurring without the influence of humans. Although we haven’t cataloged every species on Earth, using only reasonable estimates of the number of vertebrate species on this planet one can calculate that it would only take a few millennia at this rate for humans to produce the 6th mass extinction, wiping out more than 75% of the species on Earth. Some other groups of organisms, such as insects, may be suffering at rates even beyond those of vertebrates. Humans may already be a spike on this plot comparable to the intensity of the end-Cretaceous extinction.

One time I had an instructor describing the rocks of the early Triassic, just after the largest mass-extinction, as “pretty barren”. The planet Earth was a hostile place for life at that time, and the rocks show it; there just aren’t a lot of fossils because there weren’t a lot of survivors. Eventually life recovered, but it took time, and life didn’t look the same as it did beforehand. In the space of only a few millennia, humans are approaching being a geologic force of the same intensity.

These results are particularly important because humans rely on the world’s biodiversity. Organisms are used for food, for pollination, to help control pests and diseases, and even to shape the ecosystem we live in. There are some species that modern civilization simply cannot do without; that’s one reason why this Earth Day theme matters.

On a page like this, I usually try to focus on the scientific consequences of these actions, but in summary, it’s also worth asking about the moral case. We’re one species on this world; are we really ok with leaving nothing behind but a graveyard? Are we ok with one of our legacies being the 6th mass extinction?

-JBB

Image credit: https://commons.wikimedia.org/wiki/File:Phanerozoic_Biodiversity.png

Earth day 2019: https://www.earthday.org/campaigns/endangered-species/earthday2019/

References: https://science.sciencemag.org/content/360/6393/1080.2 https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0185809 https://royalsocietypublishing.org/doi/full/10.1098/rspb.2012.2845 https://www.nature.com/articles/nature09678 https://advances.sciencemag.org/content/1/5/e1400253

Labeled as a muscovite schist - the elongate grains are the mica minerals.

The End Ordovician Mass Extinction This plot shows “extinction intensity”, defined as the fraction of genera that go extinct over a short time period. There are thought to be 5 major mass extinctions during the Phanerozoic, marked and labeled on this graph. The first of these on the list is the end-Ordovician. Because it is so long ago, scientists are still working to understand the cause. A new paper measured geochemistry of rocks crossing this boundary from what is today South China and found a pair of high-mercury layers at that boundary. One possibility is that this high mercury content represents the output from extremely active volcanoes, as is thought to be the driver of the end-Permian Mass Extinction (https://tmblr.co/Zyv2Js2OUCRsV). However, as of now there is no known “Large Igneous Province” at the time, leaving plenty more work to do to understand this extinction. -JBB Image credit: https://commons.wikimedia.org/…/File:Extinction_Intensity.s… Original paper: http://geology.geoscienceworld.org/content/45/7/631

Using Instagram for mineral identification - they agreed on Chlorite in the comments for the fibrous mineral at the center, although they weren’t able to find any of the traditional green color in plane polarized light.

New evidence for the causes of slow recovery at the P-T extinction event.

The Permian-Triassic extinction (also known as the P-T boundary event), occurring 252.28 Ma has been described as the worst mass extinction of all time. Informally known amongst geoscientists as the “Great Dying” it is estimated that 96% of marine species and 70% of terrestrial species became extinct over a period of three “pulses”. Many reasons have been put forward for the cause of the extinction, and a commonly accepted theory is that the first two pulses were caused by a gradual environmental change and the last was caused by a catastrophic event. Reasons for the catastrophic event have included bolides, extreme volcanism (from the Siberian traps) and marine methane clathrate release leading to cataclysmic changes in the oceans, and there is ample evidence for widespread ocean anoxia during the P-T event.

Biotic recovery was slow, with some palaeontologists estimating that ecosystems took up to 30 million years to recover, and new research undertaken by Ohio State University doctoral student Alexa Sedlacek has suggested that the first stage of recovery (which took around 5 million years) may have been this slow as due to global warming. There is plenty of evidence in the rock record for there being little life (except for disaster taxa- that is, species that are opportunistic and will quickly colonise after ecosystem-collapse events) after the P-T and Alex has been quoted as saying “ It's as if life had a 5-million-year hangover”, and Alexa thinks she’s figured out why.

During the early Triassic there were a series of “giant volcanic eruptions” , known as The Siberian traps (these volcanic eruptions are also believed to be a cause of the extinction as there is evidence they were erupting during the late Permian) and they are estimated to have released up to 4million cubic km of lava, and the gases associated with this would have dramatically altered the atmosphere chemically. Analyses from the rocks gathered in Alexa’s research ( all of the samples came from a limestone in Iran, which was once a tropical sea) show that for the 5 million years after the P-T event, both the atmosphere and the carbon-cycle were unstable, and it wasn't just the Co2 levels they analysed. Also analysed as part of this research were the strontium ratios. Analysis indicates that there was a change in the strontium ratios in the early Triassic oceans from 0.7070 to 0.7082. And, whilst this doesn't seem like a significant change, it actually goes a long way to explain why so much of the marine life died out, and took such a long time to recover. Even this small change was enough to make the oceans hostile and unlivable.

These types of strontium ratio changes would have turned the oceans into a warm (some estimates have suggested temperatures of up to 42C- Although itemperature changes are attributed to other causes), acidic, gloopy (The gloopiness would have come from the changes in strontium ratios. An increase in this ratio indicates increased chemical weathering on the surface of the Earth, and this sediment has to end up somewhere!) mess. As warm as a modern hot-tub and filled with sediment- it’s no wonder that 96% of marine life became extinct, and took so long to recover! For example “Fish would have had silt in their gills, coral reefs would have been buried” and as far as the evidence shows, the only things that really thrived under these conditions were microbes.

So why is this important? Well studying the past can be a good way to predict what is going to happen in the future. Whilst we can all accept that changes in the climate of our Earth are natural- I mean, the evidence taken from causes of the P-T evidence proves that there are natural, and extreme, climate variations- it is impossible to deny that anthropogenic emissions are forcing our climate in ways that they are not meant to. Our oceans are getting warmer (predictions see them as reaching 27C before long, and whilst not as severe as 42C, it is still much warmer than they have been in present times), they are becoming more acidic and our marine life is already facing huge problems, with extinctions occurring at alarming rates. The message from this research is clear. We can’t wait until tomorrow to do something about anthropogenically induced climate forcing, as the roads to recovery are long, and we might just wipe ourselves out too.

For more information head to the links provided below.

-LL

http://www.sciencedaily.com/releases/2012/11/121105081238.htm

http://science.nasa.gov/science-news/science-at-nasa/2002/28jan_extinction/

http://science.nationalgeographic.com.au/science/prehistoric-world/mass-extinction/

Image; P-T boundary at Sambullak, thanks to the University of Bristol._ _

EVIDENCE FOR A RAPID REVERSAL OF THE GEOMAGNETIC FIELD 41,000 YEARS AGO

Magnetic studies performed on sediment cores from the Black Sea by the GFZ German Research Centre for Geosciences show that Earth experienced a rapid (over 440 year period) and complete reversal of the geomagnetic field 41,000 years ago, during the last ice age. Geomagnetic reversals result in the interchanging of the positions of magnetic north and magnetic south. As this was a brief and unsustained pole reversal, it is known as a geomagnetic excursion and not a full reversal. The evidence for this brief pole reversal is further bolstered by data obtained from additional studies performed in the North Atlantic, the South Pacific and Hawaii; together this shows the polarity reversal was a global event. The sediment cores also provide further evidence for the last ice age and a supervolcano eruption.

Earth has had several pole reversals in the last 20 million years, with a complete pole reversal occurring about every 200,000 to 300,000 years. The last major pole reversal occurred approximately 780,000 years ago and is known as the Brunhes–Matuyama reversal. A reversal does not happen instantly, and typically takes between 1,000 and 10,000 years. The Brunhes–Matuyama reversal caused no drastic changes in plant or animal life as provided by evidence from the fossil record. By looking at oxygen isotope ratios in deep ocean sediment cores, no changes in glacial activity were found for this period either.

The field geometry of reversed polarity for the geomagnetic excursion of 41,000 years ago lasted about 440 years and the field strength was only about 25% of today’s field. The actual polarity lasted only 250 years, which is remarkably short. During this 250-year period, the magnetic field was only at 5% of today’s field strength. This significantly lowered Earth’s protection against hard cosmic rays, which in turn led to an increased exposure to radiation. Evidence for this is shown by peaks of radioactive beryllium (10Be) in ice cores recovered from the Greenland ice sheet.

10Be is formed in Earth’s atmosphere through the collision of cosmic rays with atoms. 10Be has a half-life of 1.36 million years before decaying to 10Boron. Periods of high solar activity decrease the flux of cosmic rays that hit Earth, so the production of 10Be is inversely proportional to solar activity and increased solar wind.

This geomagnetic excursion has been known about for 45 years, after the analysis of the magnetisation of several lava flows near the village Laschamp near Clermont-Ferrand in the Massif Central. The magnetisation of these lava flows differed significantly from the direction of the geomagnetic field today. This feature has since been known as the 'Laschamp event'. Before the latest work by the GFZ, the Laschamp event was shown only by point readings of the geomagnetic field during the last ice age. This new research gives a more complete view.

The sediment cores from the Black Sea not only show the geomagnetic excursion of 41,000 years ago, they also indicate several abrupt climate changes during the last ice age. These climate changes were already known from the Greenland ice cores, but now there is a high synchronisation between the data records from the Black Sea and Greenland. The sediment cores also document the largest volcanic eruption in the Northern hemisphere of the last 100,000 years: the eruption 39,400 years ago of a super volcano near Naples, Italy, known as the Campanian Ignimbrite super-eruption. About 350 cubic kilometres of rock and lava were expelled from the volcano and spread over the eastern Mediterranean and as far as central Russia.

Interestingly, one of the Neanderthal extinction hypotheses (Neanderthals became extinct around 30,000 years ago) involves climate change. During the last ice age, Europe changed into a semi-arid desert and it is speculated that Neanderthals did not adapt their hunting techniques to this new environment. Volcanic eruptions, such as the super eruption near Naples 39,400 years ago, also may have contributed to a reduction in food supply.

Excavations at Mezmaiskaya Cave in the Caucasus Mountains of southern Russia showed there was also a reduction in plant pollen at the time. Two distinct layers of volcanic ash were observed in the cave, which coincided with large-scale volcanic events that occurred around 40,000 years ago. The first volcanic event is the Campanian Ignimbrite super-eruption. The second volcanic layer coincides with the end of Neanderthal presence at Mezmaiskaya and coincides with a smaller eruption thought to have occurred around the same time in the Caucasus Mountains.

-TEL

More on pole reversals: http://www.nasa.gov/topics/earth/features/2012-poleReversal.html

Sources: http://www.alphagalileo.org/ViewItem.aspx?ItemId=124996&CultureCode=en http://www.sciencedaily.com/releases/2010/10/101006094057.htm

Nowaczyk, N. R.; Arz, H. W.; Frank, U.; Kind, J.; Plessen, B. (2012): “Dynamics of the Laschamp geomagnetic excursion from Black Sea sediments” Earth and Planetary Science Letters, 351-352, 54-69. doi:10.1016/j.epsl.2012.06.050.

Liubov Vitaliena Golovanova, Vladimir Borisovich Doronichev, Naomi Elancia Cleghorn, Marianna Alekseevna Koulkova, Tatiana Valentinovna Sapelko, and M. Steven Shackley. Significance of Ecological Factors in the Middle to Upper Paleolithic Transition. Current Anthropology, 2010; 51 (5): 655 DOI: 10.1086/656185

Image: © Dr. habil. Norbert R. Nowaczyk / GFZ

Anthropogenic global warming claims its first mammalian victim.

This little critter is no more...The Bramble Cay melomys (aka mosaic tailed rat) was once the only mammal endemic to Australia's Great Barrier Reef, living on a single 350x150x3 metre island in the Torres Strait and therefore highly vulnerable, but it will not be the last. Indeed research published last year in Science (linked below) reveals that fully one sixth of species may vanish as the world warms, from endemics like this one with restricted ranges through Alpine species that will be literally upwards pushed off mountains and many others in a wide variety of ecological situations.

It was already critically endangered having the smallest range of any Australian mammal and hadn't been spotted since 2009, but a comprehensive survey two years ago confirmed its continued absence from its former home. And a recent report has recommended that its status be changed to 'extinct'. The cause is listed as sea level rise, since the island has been repeatedly flooded in storm surges over the last few years, killing the animals and ravaging their sole habitat. The area of island above high tide has also shrunk from 2.2 hectares in 2004 to 0.065 a decade later. Sea level is rising in the Torres Strait at around twice the global average. Scientists are crossing their fingers that an undiscovered population might lurk in the jungles of Papua New Guinea, from where they think the critters might have arrived in the first place.

While species like this are expected to be the first to go, as global warming bites many more with wider ranges are going to be squeezed out, and that is before other forms of human induced habitat destruction (which are plentiful) are factored into the situation.

Loz

Image credit: Queensland government

http://bit.ly/1UMNfo5 http://bit.ly/1rtLAcN Original report, free access: http://bit.ly/1Q0prOW Original paper on one in six species facing climate change extinction, paywall access: http://bit.ly/1XuBFBF

Amphibian Decline

It has been about 25 years since declining populations of amphibians were first noted. Amphibians, by their natures, are considered indicator species. Because amphibians have thin skin and live part their lives as aquatic animals and part on land, they are easily affected by adverse conditions in their habitat. Thus, the decline of populations in an area is an indication that something within that ecosystem is wrong.

A number of studies have been done that examine decline or extinction of populations, with the goal of developing conservation plans to slow or stop the loss of amphibians. Over the years, while studies in specific localities identified a range of stressors affecting populations of amphibians, there was little data available on a broader geographic scale. A recent study took four major stressors and looked at their effects on 83 species in 61 areas across the U.S, mainly in Federally-protected or state protected areas. The study examined the effects of human influence, changes in precipitation patterns, average annual pesticide applications, and suitability of the area for Chytrid disease (a fungal infection caused by Batrachochytrium dendrobatidis).

The main finding of the study was that although there is still definite decline within all of the study sites, no single cause of the decline could be determined on a continental basis. Geographically, the number and intensity of the threat factors varied, as well as what combination of the four stressors affected a particular study area. The recommendation of the study team was that conservation efforts must be determined and implemented at the local level, aimed at the specific threat or combination of threats contributing to decline or extinction of populations at that locality. CW

Image

http://bit.ly/1KrlL0z

Sources

http://www.nature.com/articles/srep25625

http://ces.iisc.ernet.in/biodiversity/amphibians/ecological.htm

http://edis.ifas.ufl.edu/uw233

http://bit.ly/1Ubzkvc

Shocked

This researcher is using a petrographic microscope to examine a mineral grain recovered from the just-completed effort to core and sample the rim of the crater generated during the Chicxulub Impact on the shores of what is today the Yucatan Peninsula (https://tmblr.co/Zyv2Js237-vel). The monitor shows the grain being seen under the microscope and also adds a scalebar.

The projected image is a grain of very fine sand only a hundred or so micrometers across. You’re actually looking at a bit of a sand grain that was shocked during the impact that killed the dinosaurs and was recovered from that drill core.

When an asteroid impacts a planet, part of the energy of that impact is converted into a shock wave. That wave propagates outwards through everything, distorting the atomic structures of every mineral grain it travels through. As the wave passes, first atoms are squeezed together, then they move back apart after the wave releases.

Shock waves can do lots of damage as they pass through a mineral. Some minerals can take the stress, but others fracture and some even completely melt. The mineral quartz responds to shock by producing “planar deformation features” – basically specific planes in the mineral have been kinked or broken, creating features that can be seen under a microscope.

The pattern of lines defined by the dark dots running from the upper left to the lower right of this grain establishes that it is a bit of shocked quartz (https://t.co/1N6HchliLV), a relic of the Chicxulub impact. The initial coring of this site is now complete and 1300 meters of core through the ring of the crater have been collected. They will now be taken back to facilities in the US and Germany where they will be opened and characterized.

-JBB

Image credit: Max Alexander/B612/Asteroid Day/BBC http://www.bbc.com/news/science-environment-36377679

Reference: http://bit.ly/1Z0rliw