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John Gallop

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Biases in 6th mass extinction event?

According the fossil record the earth has exhibited 5 mass extinctions and we are currently undergoing, according the masses, the biggest extinction in earths history (the 6th mass extinction)! However, no one has ever mentioned possible biases in this information that may make it seem more organisms are going extinct compared to previous mass extinctions based on the fossil record.

For a fossil to form, there is a select set of conditions needed for fossilization to occur (moisture, mud etc) and in that respect not everything fossilizes thus, there is a lot about previous ecological communities and community composition, species abundance and community structure that we can not view based on the limitted information provided by the fossil record.

Now we are in the 21st century, the first time in history where humans can observe this mass extinction and apparently species extinction rate is off the roof and reaching numbers never seen before! However, I have neve heard one adress that maybe the reason why these extinction rates are soo high compared to previous extinctions is due to us actually being around in this era visualy observing this mass extinction. Now in this era we are not just solely using the fossil record to determine mass extinction rates but we are actually visualy observing these events. As opposed to previous mass extinctions we are using more tools than the fossil record to determine extinction rates. By having more "tools" (visualing witnessing extinctions, live sampling etc) we are gaining more data and information that solely the fossil record could not provide. It is the use of these multiple tools which give us a more accurate view of these mass extinctions which can result in having higher extinction rates for this era as opposed to previous records. I am in no way saying we aren't undergoing a mass extinction however, I am just addressing possible biases that scientist seem to never adress.

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    Apr 12 2011: I think most of the data sampling/analysis is carried out in a robust way. Excluding 'live sampling' much of the anaylsis is based on isotope ratios, carbon chemistry (in the oceans), and other proxies. Currently retrievd samples are compared to the background rate through these chemical signatures, and these can provide a good clue to the expected rate of extinction, or possible extinction/s in the case of ocean acidification. So above and beyond a 'one on one' comparison of species dissaperances, the environmental change is well documented and more importantly has been shown to be 100-1000 times that the rate of other previous extinction events.
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      Apr 12 2011: yea I see how you use other tools such as isotope analysis in dating and I am not sure but I guess you could use that information to figure out climate variability through-out time. However, the issue is still there, this carbon dating you speak of will tell us nothing about which species are going extinct it would just give us information about climatic variables which could support findings of species declining if complimented with fossil record findings.
    • Apr 12 2011: Hi Daniel, I believe there are some issues relating to the temporal resolution of various dating methods compared to the high temporal resolution that we have from modern observations. There are also some issues relating to gaps in the fossil record. I would be very interested to hear what Dr. Barnosky has to say. John could you share that with us when he responds, please? Cheers.
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        Apr 12 2011: For sure, he still hasn't responded but hopefully he is a prof who will respond. I am very interested in what he says.

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