Presentations
Dinosaurian Clades
Mammalian Clades
Human Effects
Essays
The Sixth Mass Extinction
According to much scientific research, we are on the verge of a sixth mass extinction. Many clues come from a mass extinction at the end of the Permian, in which there was a 10 degree Celsius temperature increase globally from carbon release–much like what is occurring today. This temperature increase was part of a deadly trio: global warming, ocean acidification, and ocean deoxygenation. Mammals facing this trifecta of horror would perspire in the warmth, need more food and oxygen to keep their strength up, and then die when there was even less oxygen available than they were used to. The ocean acidification even led to the demise of over 90% of all ocean life at one point, as they were unable to cope with the relatively rapid change to their environment. In fact, this is why brachiopods–once extremely numerous globally–are found few and far between today. Nearly all were wiped out while many land animals were totally unaffected. This leads to interesting questions about fossil record bias, as much of our evidence on the effects of the ocean acidifying are based on the previous prevalence and current sparsity of brachiopod fossils. If, perhaps, something in their evolutionary processes made the current shells less likely to fossilize, we could be misinterpreting a major cause of one of the most important events in our planet’s history. This could lead to terrible ramifications, such as misjudging what is currently affecting our planet, providing the improper treatment, and either letting global warming continue to harm us or making the situation even worse.
The presentation examined other ways besides brachiopod deposits in which we have used the fossil record to determine causes of previous mass extinctions (to apply to the possibility of a future one). Linear regression was used to see if the amount of samples found of various types of animal before and after extinction events could find a commonality. For example, these groups were compared: big vs small animals, sedentary vs mobile animals, predators vs prey, and surface swimmers vs sea floor swimmers. Largely the results indicated that there was no real selectiveness in who survived the mass extinction events, unless you count a slight unfavorable trend toward small, non-motile, prey, and pelagic (surface swimmer) groups (much of which makes sense, as the non-motile animals could not escape changing environments, ending the food sources of smaller prey creatures; similarly, the surface of water experiences far greater change than the sea floor in nearly every aspect and would make its inhabitants far more susceptible to danger). One particularly interesting finding was that during a Cenozoic mass extinction, smaller animals died in much larger numbers. This is in stark contrast to what we’ve observed in recent times, such as the nonexistence of megafauna in North America leading to calls for Pleistocene rewilding. The talk ended with a warning but a message of hope as well, to the tune of “there’s still time to save ourselves!” It will be interesting to see if rewilding and other methods of reducing global warming is the way to achieve that, or if we will see keystone megafauna such as hippos dying out rather than say mice.