Climate change could revive medieval megadroughts in US Southwest | Study picks apart factors that caused severe, long-lasting droughts and suggests increased risk for future


Climate change could revive medieval megadroughts in US Southwest

Study picks apart factors that caused severe, long-lasting droughts and suggests increased risk for future

Date:
July 24, 2019
Source:
Earth Institute at Columbia University

Dry pasture, central valley of California (stock image).
Credit: © AlessandraRC / Adobe Stock

About a dozen megadroughts struck the American Southwest during the 9th through the 15th centuries, but then they mysteriously ceased around the year 1600. What caused this clustering of megadroughts — that is, severe droughts that last for decades — and why do they happen at all?

If scientists can understand why megadroughts happened in the past, it can help us better predict whether, how, and where they might happen in the future.

A study published today in Science Advances provides the first comprehensive theory for why there were megadroughts in the American Southwest. The authors found that ocean temperature conditions plus high radiative forcing — when Earth absorbs more sunlight than it radiates back into space — play important roles in triggering megadroughts. The study suggests an increasing risk of future megadroughts in the American Southwest due to climate change.

Previously, scientists have studied the individual factors that contribute to megadroughts. In the new study, a team of scientists at Columbia University’s Lamont-Doherty Earth Observatory has looked at how multiple factors from the global climate system work together, and projected that warming climate may bring a new round of megadroughts.

By reconstructing aquatic climate data and sea-surface temperatures from the last 2,000 years, the team found three key factors that led to megadroughts in the American Southwest: radiative forcing, severe and frequent La Niña events — cool tropical Pacific sea surface temperatures that cause changes to global weather events — and warm conditions in the Atlantic. High radiative forcing appears to have dried out the American Southwest, likely due to an increase in solar activity (which would send more radiation toward us) and a decrease in volcanic activity (which would admit more of it) at the time. The resulting increase in heat would lead to greater evaporation. At the same time, warmer than usual Atlantic sea-surface temperatures combined with very strong and frequent La Niñas decreased precipitation in the already dried-out area. Of these three factors, La Niña conditions were estimated to be more than twice as important in causing the megadroughts.

While the Lamont scientists say they were able to pinpoint the causes of megadroughts in a more complete way than has been done before, they say such events will remain difficult for scientists to predict. There are predictions about future trends in temperatures, aridity, and sea surface temperatures, but future El Niño and La Niña activity remains difficult to simulate. Nevertheless, the researchers conclude that human-driven climate change is stacking the deck towards more megadroughts in the future.

“Because you increase the baseline aridity, in the future when you have a big La Niña, or several of them in a row, it could lead to megadroughts in the American West,” explained lead author Nathan Steiger, a Lamont-Doherty Earth Observatory hydroclimatologist.

During the time of the medieval megadroughts, increased radiative forcing was caused by natural climate variability. But today we are experiencing increased dryness in many locations around the globe due to human-made forces. Climate change is setting the stage for an increased possibility of megadroughts in the future through greater aridity, say the researchers.

Story Source:

Materials provided by Earth Institute at Columbia University. Original written by Nicole deRoberts. Note: Content may be edited for style and length.


Journal Reference:

  1. Nathan J. Steiger, Jason E. Smerdon, Benjamin I. Cook, Richard Seager, A. Park Williams, Edward R. Cook. Oceanic and radiative forcing of medieval megadroughts in the American Southwest. Science Advances, 2019; 5 (7): eaax0087 DOI: 10.1126/sciadv.aax0087

Cite This Page:

Earth Institute at Columbia University. “Climate change could revive medieval megadroughts in US Southwest: Study picks apart factors that caused severe, long-lasting droughts and suggests increased risk for future.” ScienceDaily. ScienceDaily, 24 July 2019. <www.sciencedaily.com/releases/2019/07/190724144152.htm>.

Komodo dragon lizards, new research


The Komodo dragons are the largest lizards in the world.

 

These predators weighing up to 200 pounds can detect their prey from up to 7.5 miles away. And although they are cold-blooded, they can ramp up their metabolism to near mammalian levels, which gives them great speed and endurance. However, scientists have understood little about how the DNA of these remarkable lizards encodes such astounding characteristics.
Now, a new study from researchers at the Gladstone Institutes, in a close collaboration with scientists at UC San Francisco (UCSF) and Zoo Atlanta, provides the first high-resolution sequence of the Komodo dragon, as well as insight into how it evolved.
“We started the project 9 years ago to look at how genomes evolve, but to do so, we needed the genome sequences first,” said Gladstone Senior Investigator Benoit Bruneau, PhD, a senior author of the study. “At the time, other groups had sequenced the turtle genome, snake and bird genomes, and the crocodile genome was in process, but the missing branch was the varanid lizards — the family to which Komodo dragons belong.”
“I went to Komodo Island years ago as a tourist, and I saw Komodo dragons in the wild there,” said Katherine Pollard, PhD, a senior investigator and the director of the Gladstone Institute of Data Science and Biotechnology, who is the other senior author of the study. “I never would have guessed then that I would one day work on their genome. We didn’t even have a human genome at that time!”
The team studied the DNA of two Komodo dragons from Zoo Atlanta named Slasher and Rinca, whose blood samples were obtained as part of their scheduled annual check-ups.
“This project was a great opportunity for us to learn more about Komodo dragons using the newest and best technologies, and then be able to contribute our findings toward the general knowledge of lizard biology,” said Joseph R. Mendelson III, PhD, a herpetologist and evolutionary vertebrate biologist, and the director of research at Zoo Atlanta.
The study, which was published in the journal Nature Ecology & Evolution and released on BioRxiv as a preprint with a data repository, provides an extremely high-quality sequence of the Komodo dragon genome, which can now be used as a reference in efforts to sequence other vertebrate genomes.
“Vertebrate genomes are big, and they contain many repetitive sequences,” explained Pollard, who is also a professor at UCSF and a Chan Zuckerberg Biohub investigator. “Most sequencing technologies only produce short stretches of sequence at a time. When those short stretches include repetitive elements, it’s impossible to know where they belong and what they connect to, making it hard to string them together.”
To get around this problem, the team took a multi-pronged approach.
“We used multiple technologies, including long-range sequencing and a physical mapping technique to do the assembly,” said Bruneau, who is also the director of the Gladstone Institute of Cardiovascular Disease and a professor in the Department of Pediatrics at UCSF. “As a result, we have a super deep, very high-quality sequence for the Komodo.”
Once the scientists had the sequence, they used computational tools to compare it to that of other reptiles and see what makes the Komodo dragon genome unique.
Specifically, they were looking for changes in the genome that helped the Komodo dragon adapt to its environment, which have undergone an evolutionary process called positive selection. A remarkable finding was that positive selection has shaped several genes involved in the function of mitochondria, the energy powerhouses of the cell that control how well heart and other muscles function.
“Our analysis showed that in Komodo dragons, many of the genes involved in how cells make and use energy had changed rapidly in ways that increase the lizard’s aerobic capacity,” said Abigail Lind, PhD, a postdoctoral researcher in Pollard’s lab and first author of the study. “These changes are likely key to the Komodo’s ability to achieve near-mammalian metabolism.”
Lizards are generally not known for their high aerobic capacity. In other words, they become exhausted quickly after physical exertions.
“However, we know from working with Komodo dragons that they’re capable of sustained aerobic activity, which could be swimming, running, or walking extremely long distances,” explained Mendelson, who is also an adjunct associate professor at the Georgia Institute of Technology. “Our study showed us that the secret is in these mitochondrial adaptations to increase their cardiac output. This gives us an understanding of how these animals are able to do what we had been observing.”
In addition, the researchers discovered that Komodo dragons, along with some other lizards, have an unexpectedly large number of genes that encode chemical sensors known as vomeronasal receptors. These receptors are part of a sophisticated sensory system that allows animals to detect hormones and pheromones.
This type of sensing is involved in a variety of activities, including kin recognition, mate choice, predator avoidance, and hunting. In the Komodo genome, the team found over 150 copies of one class of vomeronasal receptor genes. The team also found that many of these genes are unique to each individual lizard species, raising the possibility that the Komodo dragon’s vomeronasal receptors may function in Komodo-specific ways.
“It will be interesting to determine whether this explains Komodo dragons’ ability to detect prey over such large distances,” said Bruneau. “One of the exciting things about this project is that we didn’t know what to expect. This was an opportunity to look at a genome and say, ‘Tell me the story of your organism.'”
Next, Bruneau and his team are looking forward to using their findings to investigate how genes that control the formation of the vertebrate heart have changed over the course of evolution, as most reptiles have only a three-chambered heart, while mammals have four chambers.
The completed genome sequence also represents an invaluable resource for conservation biologists interested in tracking Komodo dragons to study their ecology, and for the many scientists across the world investigating vertebrate evolution.
“The significance of this study far exceeds Komodo dragons,” said Mendelson. “It gives us a framework to compare other sequenced animals and understand the genetic basis for how all their characteristics have evolved. This project also brings to the forefront the importance of preserving biodiversity, and the important role zoos can play in broad-scale research without being injurious to the animals in our care.”

Story Source:
Materials provided by Gladstone Institutes. Note: Content may be edited for style and length.

Journal Reference:
Abigail L. Lind, Yvonne Y. Y. Lai, Yulia Mostovoy, Alisha K. Holloway, Alessio Iannucci, Angel C. Y. Mak, Marco Fondi, Valerio Orlandini, Walter L. Eckalbar, Massimo Milan, Michail Rovatsos, Ilya G. Kichigin, Alex I. Makunin, Martina Johnson Pokorná, Marie Altmanová, Vladimir A. Trifonov, Elio Schijlen, Lukáš Kratochvíl, Renato Fani, Petr Velenský, Ivan Rehák, Tomaso Patarnello, Tim S. Jessop, James W. Hicks, Oliver A. Ryder, Joseph R. Mendelson, Claudio Ciofi, Pui-Yan Kwok, Katherine S. Pollard, Benoit G. Bruneau. Genome of the Komodo dragon reveals adaptations in the cardiovascular and chemosensory systems of monitor lizards. Nature Ecology & Evolution, 2019; 3 (8): 1241 DOI: 10.1038/s41559-019-0945-8

Dear Kitty. Some blog

This 11 May 2019 video says about itself:

The Raw Nature crew observe Komodo dragons hunting in the wild during a visit to Rincah Island in Indonesia. They then demonstrate the effect of the powerful Komodo venom on a piece of raw meat.

From the Gladstone Institutes in the USA:

Komodo dragon genome reveals clues about its evolution

July 29, 2019

Summary: A new study provides the first high-resolution sequence of the Komodo dragon, as well as insight into how it evolved.

The Komodo dragons are the largest lizards in the world. These predators weighing up to 200 pounds can detect their prey from up to 7.5 miles away. And although they are cold-blooded, they can ramp up their metabolism to near mammalian levels, which gives them great speed and endurance. However, scientists have understood little about how the DNA of these remarkable lizards encodes such astounding characteristics.

Now…

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Hallo Arschloch-Kind! Emily wird heute sterben!


Gutes Karma to go ®

Hallo Arschloch-Kind! Emily wird heute sterben!

Du erinnerst dich vielleicht an das Taubenkind, das du mit deinen Freunden aus purer Lust an der Grausamkeit und Machtgefühl, als Fussball benutzt hast? Wie ihr Emily immer wieder brutal mit euren Füssen getreten habt und einander zugekickt, bis sie innerlich nur noch ein blutiger Klumpen Gewebe und zersplitterter Knochen war?
Hast du hören können, wie ihre zarten Flügel brachen, gab es ein Geräusch oder ging das in eurem Gelächter unter?
War es nicht ein Mordsspaß, als sie verzweifelt mit den kleinen Flügeln flatterte und nach ihren Vogeleltern rief?

emily

Ich weiß nicht, wo Emilys Vogeleltern in diesem Augenblick waren, deine Arschloch-Eltern waren jedenfalls dabei und sahen keinen Grund, dich darauf hinzuweisen, dass man Wehrlose und Schwächere nicht quält. Auch die Arschloch-Passanten in der Fussgängerzone fanden das offenbar OK, denn sie gingen alle achtlos vorbei, während ihr mit jedem Tritt feine, filigrane Knochen zertrümmert habt…

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Vie d’un écrivain français : le Journal littéraire, de Paul Léautaud


Journal littéraire, Paul Léautaud, Gallimard, coll. « Folio », 2013, anthologie composée par Pascal Pia et Maurice Guyot (Première éd. 1968)

Brumes, blog d'un lecteur

Léautaud 1954

Journal littéraire, Paul Léautaud, Gallimard, coll. « Folio », 2013, anthologie composée par Pascal Pia et Maurice Guyot (Première éd. 1968)

Paul Léautaud a fait inscrire sur sa tombe une intrigante épitaphe : « Écrivain français » (Jean Dutourd est le seul, à ma connaissance, à l’avoir reprise). Ses lecteurs savent que ce n’est pas là une proclamation de patriotisme acharné. Il n’était pas un fanatique de la nation, un apologue de la France et de sa grandeur. Si les guerres excitaient son appétit de spectateur goguenard des passions humaines, elles ne l’ont pas porté à défendre une « patrie » dans laquelle il ne s’est jamais reconnu. Pour cet individualiste anarchisant et antimilitariste, la France ne signifiait pas grand-chose. Son fameux Journal littéraire le répète assez, acrimonieux envers tous les « rossignols des carnages », qui chantaient la guerre pendant les massacres de 14-18 et de 39-45. Il n’était pas de ceux qui pardonnaient aux écrivains de…

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