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Mass extinction survival is more than just a numbers game

Widespread species are at just as high risk of being wiped out as rare ones after global mass extinction events, says new research by University of Leeds scientists.
There have been five mass extinction events in the Earth's history, including climate change caused by volcanoes and an asteroid hit that wiped out the dinosaurs.
In general, geographically widespread animals are less likely to become extinct than animals with smaller geographic ranges, offering insurance against regional environmental catastrophes.

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Earth 'entering new extinction phase'

The Earth has entered a new period of extinction, a study by three US universities has concluded, and humans could be among the first casualties.
The report, led by the universities of Stanford, Princeton and Berkeley, said vertebrates were disappearing at a rate 114 times faster than normal.

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Mass extinctions
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Title: Giant comets and mass extinctions of life
Author: W. M. Napier

I find evidence for clustering in age of well-dated impact craters over the last 500 Myr. At least nine impact episodes are identified, with durations whose upper limits are set by the dating accuracy of the craters. Their amplitudes and frequency are inconsistent with an origin in asteroid breakups or Oort cloud disturbances, but are consistent with the arrival and disintegration in near-Earth orbits of rare, giant comets, mainly in transit from the Centaur population into the Jupiter family and Encke regions. About 1 in 10 Centaurs in Chiron-like orbits enter Earth-crossing epochs, usually repeatedly, each such epoch being generally of a few thousand years duration. On time-scales of geological interest, debris from their breakup may increase the mass of the near-Earth interplanetary environment by two or three orders of magnitude, yielding repeated episodes of bombardment and stratospheric dusting. I find a strong correlation between these bombardment episodes and major biostratigraphic and geological boundaries, and propose that episodes of extinction are most effectively driven by prolonged encounters with meteoroid streams during bombardment episodes. Possible mechanisms are discussed.

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Plants survive better through mass extinctions than animals

At least 5 mass extinction events have profoundly changed the history of life on Earth. But a new study led by researchers at the University of Gothenburg shows that plants have been very resilient to those events.
For over 400 million years, plants have played an essential role in almost all terrestrial environments and covered most of the worlds surface. During this long history, many smaller and a few major periods of extinction severely affected Earths ecosystems and its biodiversity.

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Mass Extinctions
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Title: Mass Extinction And The Structure Of The Milky Way
Author: M. D. Filipovic , J. Horner , E. J. Crawford , N. F. H. Tothill

We use the most up to date Milky Way model and solar orbit data in order to test the hypothesis that the Sun's galactic spiral arm crossings cause mass extinction events on Earth. To do this, we created a new model of the Milky Way's spiral arms by combining a large quantity of data from several surveys. We then combined this model with a recently derived solution for the solar orbit to determine the timing of the Sun's historical passages through the Galaxy's spiral arms. Our new model was designed with a symmetrical appearance, with the major alteration being the addition of a spur at the far side of the Galaxy. A correlation was found between the times at which the Sun crosses the spiral arms and six known mass extinction events. Furthermore, we identify five additional historical mass extinction events that might be explained by the motion of the Sun around our Galaxy. These five additional significant drops in marine genera that we find include significant reductions in diversity at 415, 322, 300, 145 and 33 Myr ago. Our simulations indicate that the Sun has spent ~60% of its time passing through our Galaxy's various spiral arms. Also, we briefly discuss and combine previous work on the Galactic Habitable Zone with the new Milky Way model.

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Title: Assessing the influence of the solar orbit on terrestrial biodiversity
Authors: F. Feng, C.A.L. Bailer-Jones

The terrestrial fossil record shows a significant variation in the extinction and origination rates of species during the past half billion years. Numerous studies have claimed an association between this variation and the motion of the Sun around the Galaxy, invoking the modulation of cosmic rays, gamma rays and comet impact frequency as a cause of this biodiversity variation. However, some of these studies exhibit methodological problems, or were based on coarse assumptions (such as a strict periodicity of the solar orbit). Here we investigate this link in more detail, using a model of the Galaxy to reconstruct the solar orbit and thus a predictive model of the temporal variation of the extinction rate due to astronomical mechanisms. We compare these predictions as well as those of various reference models with paleontological data. Our approach involves Bayesian model comparison, which takes into account the uncertainties in the paleontological data as well as the distribution of solar orbits consistent with the uncertainties in the astronomical data. We find that various versions of the orbital model are not favoured beyond simpler reference models. In particular, the distribution of mass extinction events can be explained just as well by a uniform random distribution as by any other model tested. Although our negative results on the orbital model are robust to changes in the Galaxy model, the Sun's coordinates and the errors in the data, we also find that it would be very difficult to positively identify the orbital model even if it were the true one. (In contrast, we do find evidence against simpler periodic models.) Thus while we cannot rule out there being some connection between solar motion and biodiversity variations on the Earth, we conclude that it is difficult to give convincing positive conclusions of such a connection using current data.

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The Race to Catalogue Living Species Before They Go Extinct

The U.S. has spent several billion dollars looking for life on other planets. Shouldnt we spend at least that much finding and identifying life on Earth?
That is the argument behind a taxonomy analysis by a trio of scientists in Science, published on January 25.

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Attenborough's ark

In his 60th year of broadcasting, naturalist Sir David Attenborough has highlighted the plight of 10 weird and wonderful species he would like to save from extinction.
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Toxic seas 'spurred' extinctions of dinosaurs and many other species

Poisonous seawater probably may have driven two of the earth's best-known mass extinctions, say Penn State University researchers.
It is understood that an asteroid the size of Mt. Everest ended the reign of the dinosaurs when it struck Mexico's Yucatan Peninsula 65 million years ago. The impact resulted firestorms, darkness and deadly gases that made trouble for life on land.
According to geochemist Lee Kump of Penn State University, something more was going on in the oceans, where 93 percent of nannoplankton-the base of the marine food web-went extinct.
Dust and smoke kicked up by the asteroid would have throttled photosynthesis for several months, but it took some 270,000 years for plankton populations to bounce back.
Even in the Northern Hemisphere, which suffered a direct hit, recovery should have been much faster. In 2010 Kump and some of his Penn State colleagues explained this lag by proposing that toxic metals from the asteroid contaminated the oceans.

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60 Myr periodicity
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Title: A ~60 Myr periodicity is common to marine-87Sr/86Sr, fossil biodiversity, and large-scale sedimentation: what does the periodicity reflect?
Authors: Adrian L. Melott (Kansas), Richard K. Bambach (National Museum of Natural History), K. D. Petersen (Aarhus Univ.), John M. McArthur (University College London)

We find that the marine 87Sr/86Sr record shows a significant periodicity of 59.3 3 Myr. The 87Sr/86Sr record is 171 12 out of phase with a 62 3 Myr periodicity previously reported in the record of marine-animal diversity. These periodicities are close to 58 4 Myr cycles found for the number of gap-bounded sedimentary carbonate packages of North America We propose that these periodicities reflect the operation of a periodic "pulse of the Earth" in large-scale, Earth processes. These may be linked to mantle or plate-tectonic events, possibly uplift, which affects Earth's climate and oceans, and so the geochemistry, sedimentation, and biodiversity of the marine realm. Alternately, they may be linked to oscillation of the solar system normal to the plane of the galaxy.

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