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New Extinction Theory

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  • 30-03-2009 8:10pm
    #1
    Registered Users Posts: 30,746 ✭✭✭✭


    Not the extinction that killed off the dinosaurs, but rather the one that paved the way forward for them to dominate the world.
    Russian scientists have devised a new theory about the Permian extinction (250million years ago) where around 90% of land animals died out, the biggest mass extinction known. They claim that emissions from giant salt lakes into Earth's atmosphere may have caused catastrophic damage to the world's plant life, leading to the mass die off.

    Read more here.
    The largest mass extinction in the history of the Earth could have been triggered off by giant salt lakes, whose emissions of halogenated gases changed the atmospheric composition so dramatically that vegetation was irretrievably damaged. At least that is what an international team of scientists have reported in the most recent edition of the 'Proceedings of the Russian Academy of Sciences. ' At the Permian/Triassic boundary, 250 million years ago about 90 percent of the animal and plant species ashore became extinct. Previously it was thought that volcanic eruptions, the impacts of asteroids, or methane hydrate were instigating causes. The new theory is based on a comparison with today's biochemical and atmospheric chemical processes. 'Our calculations show that airborne pollutants from giant salt lakes like the Zechstein Sea must have had catastrophic effects at that time,' states co-author Dr Ludwig Weissflog from the Helmholtz-Centre for Environmental Research (UFZ). Forecasts predict an increase in the surface areas of deserts and salt lakes due to climate change. That is why the researchers expect that the effects of these halogenated gases will equally increase.

    The team of researchers from Russia, Austria, South Africa and Germany investigated whether a process that has been taking place since primordial times on Earth could have led to global mass extinctions, particularly at the end of the Permian. The starting point for this theory was their discovery in the south of Russia and South Africa that microbial processes in present-day salt lakes naturally produce and emit highly volatile halocarbons such as chloroform, trichloroethene, and tetrachloroethene. They transcribed these findings to the Zechstein Sea, which about 250 million years ago in the Permian Age, was situated about where present day Central Europe is. The Zechstein Sea with a total surface area of around 600.000 sq. km was almost as large as France is today. The hyper saline flat sea at that time was exposed to a predominantly dry continental desert climate and intensive solar radiation - like today's salt seas. 'Consequently, we assume that the climatic, geo-chemical and microbial conditions in the area of the Zechstein Sea were comparable with those of the present day salt seas that we investigated,' Weissflog said.

    In their current publication the authors explain the similarities between the complex processes of the CO2-cycle in the Permian Age as well as between global warming from that time and at present. Based on comparable calculations from halogenated gas emissions in the atmosphere from present-day salt seas in the south of Russia, the scientists calculated that from the Zechstein Sea alone an annual VHC emissions rate of at least 1.3 million tonnes of trichloroethene, 1.3 million tonnes of tetrachloroethene, 1.1 million tonnes of chloroform as well as 0.050 million tonnes of methyl chloroform can be assumed. By comparison, the annual global industrial emissions of trichloroethene and tetrachloroethene amount to only about 20 percent of that respectively, and only about 5 percent of the chloroform from the emissions calculated for the Zechstein Sea by the scientists. Incidentally, the industrial production of methyl chloroform, which depletes the ozone layer, has been banned since 1987 by regulation of the Montreal Protocol.

    'Using steppe plant species we were able to prove that halogenated gases contribute to speeding up desertification: The combination of stress induced by dryness and the simultaneous chemical stressor 'halogenated hydrocarbons' disproportionately damages and destabilise the plants and speeds up the process of erosion,' Dr Karsten Kotte from the University of Heidelberg explained.

    Based on both of these findings the researchers were able to form their new hypothesis: At the end of the Permian Age the emissions of halogenated gases from the Zechstein Sea and other salt seas were responsible in a complex chain of events for the world's largest mass extinction in the history of the Earth, in which about 90 percent of the animal and plant species of that time became extinct.

    According to the forecast from the International Panel on Climate Change (IPCC), increasing temperatures and aridity due to climate change will also speed up desertification, increasing with it the number and surface area of salt seas, salt lagoons and salt marshlands. Moreover, this will then lead to an increase in naturally formed halogenated gases. The phytotoxic effects of these substances become intensified in conjunction with other atmospheric pollutants and at the same time increasing dryness and exponentiate the eco-toxicological consequences of climate change.

    The new theory could be like a jigsaw piece that contributes to solving the puzzle of the largest mass extinction in the history of the Earth. 'The question as to whether the halogenated gases from the giant salt lakes alone were responsible for it or whether it was a combination of various factors with volcanic eruptions, the impact of asteroids, or methane hydrate equally playing their role still remains unanswered,' Ludwig Weissflog said. What is fact however is that the effects of salt seas were previously underestimated. In their publication the researchers working with Dr Ludwig Weissflog from the UFZ and Dr Karsten Kotte from the University of Heidelberg want to prove that recent salt lakes and salt deserts of south-east Europe, Middle Asia, Australia, Africa, America can not only influence the regional but also the global climate. The new findings on the effects of these halogenated gases are important for revising climate models, which form the basis for climate forecasts.

    Inostrancevia_and_Scutosaurus.jpg
    Inostrancevia alexandri attacking Scutosaurus karpinski by Kelly Taylor.


Comments

  • Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 91,636 Mod ✭✭✭✭Capt'n Midnight


    were there any extinctions associated with the med going dry six million years ago ?


  • Registered Users Posts: 30,746 ✭✭✭✭Galvasean


    were there any extinctions associated with the med going dry six million years ago ?

    6mya? Hmm, that would be near the end of the Miocene. There was a relatively small mass extinction (estimates vary, but under 30%) during the Miocene, although that was about 15 million years ago and has been attributed to a meteor impact in Germany and subsequent volcanic activity.

    If there was a proportionately high volume of extinctions at that time in that region I am not currently aware of it and haven't been able to find much information on google.


  • Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 91,636 Mod ✭✭✭✭Capt'n Midnight


    http://www.zechsteinmagnesium.com/
    map.jpg
    That sea is much smaller than the med so the effects should be more , unless there is another mechanism involved.


  • Hosted Moderators Posts: 11,362 ✭✭✭✭Scarinae


    That's really interesting, I hadn't heard anything about that hypothesis before, thanks for sharing!

    As for the drying of the Mediterranean, it was indeed during the Miocene epoch, during a subsection called the Messinian. Gypsum and other evaporites are fairly abundant, I couldn't tell you though if these would have any effects on extinction rates because I am unfamiliar with the concept! It definitely caused regional extinction - for example, there are many palaeo coral reefs in Spain which were pretty much killed off by the resulting high salinity, and I'd say the same is true for most marine organisms - but I don't know about worldwide extinctions.
    However, it is likely that the Mediterranean basin dried out and was reflooded many times due to complicated tectonics in the region (basically caused by Africa steadily ploughing into Europe) which is thought to have opened and closed various openings between the basin and the main ocean - IIRC the opening at Gibraltar only opened in the Pliocene? - so I don't know how comparable it is with this new discovery. If you want to look it up, the buzz words would be 'Messinian Salinity Crisis', that is what the event is known as among geologists


  • Moderators, Society & Culture Moderators Posts: 9,713 Mod ✭✭✭✭Manach


    Far back in the day I was studying Geology, it was gaseous emissions from volcanic eruptions which was the attributed cause of the Permian Extinction, blocking sunlight and dropping global temperatures.


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  • Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 91,636 Mod ✭✭✭✭Capt'n Midnight


    http://www.cbsnews.com/stories/2003/11/20/tech/main584760.shtml
    Researchers studying rocks from Antarctica have found chemical evidence that a huge meteorite smashed the Earth 251 million years ago and caused the greatest extinction event in the planet's history, killing about 90 percent of all life.

    then again since the ocean floor is only 200m years old there is a 70% chance that a meteorite crater would have already disappeared.


  • Registered Users Posts: 1,353 ✭✭✭Goduznt Xzst


    Yeah, very interesting. Still I'd like to see studies on how they imagine the other 10% of life survived this. Maybe proximity to the halogenated gas emissions? Or, like it postulated, maybe it was a combination of factors over a period of time. Is it known, roughly, how long the permian/triassic extinction lasted for?


  • Registered Users Posts: 30,746 ✭✭✭✭Galvasean


    Manach wrote: »
    Far back in the day I was studying Geology, it was gaseous emissions from volcanic eruptions which was the attributed cause of the Permian Extinction, blocking sunlight and dropping global temperatures.
    http://www.cbsnews.com/stories/2003/11/20/tech/main584760.shtml

    then again since the ocean floor is only 200m years old there is a 70% chance that a meteorite crater would have already disappeared.

    Interestingly I was watching a recent episode of Horizon (admitadly not always the best source for science) which showed a possible link between large meteor impacts and massed volcanic activity. Basically a large meteor impact on one side of the planet can cause a knock on effect which causes unusually heavy volcanism on the other side of the planet. It has been theorized that this lethal combination may have been responsible for the Permian extinction.
    Still I'd like to see studies on how they imagine the other 10% of life survived this.

    It's going to be very hard to figure out what exact adaptations helped the remaining 10% survive, when we are not even certain of the exact nature of the extinction event.
    One thing that is worth consiidering is how at the time most of the world's land was merged as the 'supercontinent' of Pangea. This resulted in the land animals of the world having a relatively poor biodiversity. So when disaster struck there simply was not that much variety of animals with particularly unique adaptations. This would mean the odds of certain groups of animals to have adaptations suited to survive such a mass extinction would be comparatively (when compared to say the KT extinction) low.
    As for life in the sea, I'm not sure but perhaps the comparative lack of unique coastal habitats may have led to a similar lack of biodiversity?


  • Closed Accounts Posts: 26 I.P. Freely


    This is a very interesting thread


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