What I think are the main threats to Human Extinction..

The topic I chose to research was a fairly broad one. I knew coming into it that of course I would not find answers, nobody can predict how the human race will end. However I didn’t expect to find the trends that I did. I do feel like I have narrowed down the large spectrum down to events which have a higher chance of occurring. My research is extremely limited, and I am aware that there are many other circumstances in which species have gone extinct in the past. One thing I haven’t acknowledged in my research is the human impact on the earth which could unveil many new and undiscovered ways in which we could be diminishing our race. For 3 of the species I researched, there was no possibility that humans could have had an impact on their extinction, whereas the remaining two (Golden Toad and Harelip Sucker) went extinct amongst the presence of humans. In this post I will discuss what the main trends of extinction were and what ideas arose from my research which could be applied to and affect humans.

Rapid Change in Climate

Most of the extinctions I looked at were a result (or a flow on effect) of a rapid change in the climate. Adapting to a new environment of a cooler or warmer temperature is what seemed to be the cause of many extinctions, such as the Mastodon, which continually retreated and advanced according to where the earth was at on a glacial-inter glacial cycle to maintain a suitable environment. When the climate changed too rapidly and the mastodons could not migrate fast enough, they were killed off. Their diets were fairly specific, so another factor to include would be whether they could not physically adapt to the climate, or whether their food sources diminished before they did. Either way both factors are incredibly applicable to humans, especially at the rate the earth is warming, faster than ever before. I believe the rapid climate change could definitely be a major killer for us.

I’m no biologist, but looking at how susceptible the human body is to disease and change in comparison to other species, what makes us think that our bodies would be able to adapt so rapidly to a higher temperature environment? If we were the Mastodon 50,000 years ago, perhaps the increasing temperature would be all we had to worry about, but humans have the added factor of what actually is causing the rapid temperature increase. 50,000 years ago the change was a natural process, today the increase in temperature is man-made. So not only do we have to worry about our bodies adapting to a higher temperature, but how will our bodies adapt to the change in chemistry of the environment? Pollution is covering the planet, cities everywhere have skies flooded with pollution. It is common now in cities to have live updates on pollution as we do with weather, to see whether is safe to be walking outside that day. For example this site which gives real time pollution measurements: http://aqicn.org/city/beijing/.  The fact that these measures have even been thought about goes to show that humans are aware of how the chemistry in the atmosphere is changing, however perhaps it does not occur to everyone that potentially our bodies may only be able to cope with so much change.

Screenshot of http://aqicn.org/city/beijing/

Diminishing Resources

Throughout my research a common trend was loss of resources, which lead to extinction. We are constantly told that oil and gas are running out and eventually won’t be able to drive our cars. I agree we are using more than we can sustain, infact, we can’t sustain the amount of fossil fuels we are using – they take millions of years to make! But I don’t think it really occurs to the general public that other resources that are more essential to man than fuel one would argue, are diminishing. This was shown time and time again through my research – the Golden Toad losing its water source, the harelip sucker losing its food source due to the change in environment. Food and water is what humans rely on the most. It is a flow on effect from a rapid change in environment, whether it be a drought, a flood, a volcano eruption, it does not take a lot to ruin our food sources. If we run out of fuel as one of our resources, we cannot transport the goods from region to region, country to country. Should an event occur where it wipes out one regions food sources, the region will need to rely on other regions for food sources. There are ways to solve these issue, if the matter of diminishing resources occurs on a regional scale, the effects can be minimized. However what if this happens on a global scale? It may seem to some as unrealistic, but is it really just a matter of the chicken or the egg? Will our food sources survive the changing climate atmosphere? If our food sources adapt quicker than us humans, then of course that will prolong our lifetimes. But should our food sources diminish before we do, that will be something which could lead us to extinction.

Extra-terrestrial impact

The final idea which came to light as a result of my research is the idea that an extra-terrestrial object could cause a mass extinction. As I have mentioned in the K/T extinction post, the likelihood of a comet impacting the earth is the same as one dying in an aeroplane accident. Whether it be the direct impact of the asteroid or comet itself, or the follow on effects from it such as nuclear winters and forest fires which would in itself diminish resources, and cool down the earth to a temperature in which humans could not survive. Some may glance over this idea as it could be viewed as a matter of chance, and something out of our control. It is easier to take this perspective and focus on making changes within our planet to try to prevent the first two options – reduce human influenced change on our atmosphere, secure our resources and invest in ways to create more. However there is supposedly ways to redirect the path of asteroids, so seeing as it is proven to be a real threat to our race (refer to K/T extinction post), why are we not investing more money into removing this from even being an option?

Picture source: http://www.huffingtonpost.com/2013/08/19/nasa-asteroid-deflection-near-earth-objects-video_n_3744379.html

My Conclusions

The three ideas I have discussed have caused extinction in the past, and at the rate in which the earth is changing, I do believe that the first two options (Rapid changing in climate and diminishing resources) are inevitable. My research wasn’t incredibly extensive as I only looked at 4 different species and an extinction event, however what I looked at were all linked in some way or another by the three options I have discussed above. Given that all of the species I looked at underwent extinction events at different time periods in which the earth was at different temperatures and the atmosphere was largely different, it shows that the trends I have found are not defined by a specific environment.

My research showed how all the earth systems can interact to create new environments on the planet, and rapidly alter ones way of life. For example, within one year, El Nino – an atmospheric change –interacted with the hydrosphere, and in turn, affected the water supply in which the golden toad relied on.  What lead to the extinction of the species were not one off factors, it was the interaction of spheres in which lead to the events occurring. While most of these extinctions did not include the anthrosphere, the next question would be what effect will adding the anthrosphere to these equations mean for the extinction rate of humans? Will the anthrosphere sped up the extinction of our race, or will we be able to save ourselves?

The K/T Extinction

Extinction of the Dinosaurs

The final extinction I will look into is the ever so famous K/T extinction event which lead to the extinction of the dinosaurs. The extinction is the 2^nd largest in the history, behind the Permian, and is thought to have killed off 50% of all species at the time. The event did not have such an effect on mammals, which seemed to sail on through to the tertiary, however marine biodiversity took a large hit (The Department of Paleobiology, n.d.). While it is the most commonly known theory that an asteroid was the catastrophic event which lead to the extinction, it is a touchy subject to some scientists when trying to pin point the exact cause.

Picture Source: http://forum.mafiascum.net/viewtopic.php?p=6455051

There are two main theories about the extinction. The first is that the mass extinction was completely internally driven through volcanism and tectonic movements. The other is the more common theory that an extra-terrestrial object impacted the earth’s surface. Both theories acknowledge these facts: both vertebrates, invertebrates, marine and terrestrial species went extinct; there is a high concentration of iridium found in the K/T boundary layer; iridium can be found either from an extra-terrestrial object, or from deep in the earth’s mantle; and there was a global cooling following the K/T boundary (Smith, 2005).

The first theory suggests that the high iridium concentrations come from the mantle. The cause of this reaching the earth’s surface would be volcanism, and lots of it. It is thought that the extinction was more gradual than catastrophic. The volcanism occurred several million years before the extinction and flooded the earth with lava – evidence for this has been noted especially in India in which the lava flows dated back to 65-70 Mya. The volcanism could have generated enough dust, ash and soot to create a blanket over the earth and block out sunlight, generating a global climate change, a nuclear winter (Smith, 2005). This theory suggests that dinosaurs underwent a gradual approach to extinction.

The second theory is that the earth was struck by an extra-terrestrial object, such as a comet or meteor. The theory was somewhat confirmed to those who believed it in when a crater off the coast of the Yucatan Peninsula, Mexico, was discovered. The crater is 150km wide and dates back to 65million years ago, the year of the K/T extinction. The high abundance of iridium found in the K/T layer, and the shock quartz found within and closely above the layer provides solid evidence for this hypothesis. Following the impact, it is thought that widespread forest fires occurred. However, the impact caused cooling due to the ejecting of dust into the atmosphere, prohibiting sunlight from reaching the earth surface. Some theorists have toyed with idea that there may have been several impact events over the course of serval million years, suggesting the extinction may have been gradual (National Geographic, n.d.).

Currently the exact cause of the mass extinction is unknown. It could well be a combination of all theories – volcanism topped off with an impact event. The overall consensus is that a climate change was the most likely cause of the extinction, seeing as not just one particular type of species were effected. I have already talked about what I believe the threats to humans would be given a rapid climate change, however I have not yet discussed what would happen to humans given an impact event such as a comet. 

I recently watched a ted talk by a man named Stephen Petranek. He spoke about what he believed would be the 10 ways in which the world may end. He believes that the biggest danger to our species is that an extra-terrestrial object collides with our planet, saying it “is not a matter of if, but a matter of when and how big”. I believe it is a huge risk to humans. We are in a fixed orbit, it is a matter which is completely out of one’s control. As Stephen mentions in the video, in 1989, a large asteroid passed 400,000miles away from earth, directly through earth’s orbit. This close call was so close infact, had it been 6 hours earlier it would have collided with earth. Smaller asteroids collide with our planet around every 100 years. They contain enough impact to begin forest fires and kick up enough dust to potentially begin a nuclear winter (Patranek, 2002). The effect of Asteroids colliding with the planet is perhaps not underestimated, but the scale of how often the incident occurs is definitely underestimated. Dr Clark Chapman produced these statistics on what he believed the chances of one being killed by an asteroid/comet impact would be:

This diagram shows the findings of Dr Clark Chapman, presented by Patranek at Ted conference 2002

With the amount of money being spent on preventing deaths in floods, aircraft accidents etc, we should be seriously looking at what we can do to minimise the impacts of this event as it could be deathly should we be so unfortunate. As Stephen mentions at the end of the video, thre are ways to somewhat prevent the issue. NASA is identifying asteroids and predict whether they will encounter earth or not. This technology is more advanced than us being able to predict when a volcano will erupt. Stephen believes that with the knowledge of where the asteroid is heading, scientist can change the trajectory of the asteroid by landing a ion propulsion device on it, and while it may seem farfetched, it is extremely achievable. However because the asteroid theory is not taken as seriously as other possible deathly events in which we potentially encounter daily, without the technology or funding they may well be what could cause our extinction, as it may have the dinosaurs.

Link to TED talk with Stephen Patranek: https://www.ted.com/talks/stephen_petranek_counts_down_to_armageddon#t-1716708

References

National Geographic. (n.d.). Dinosaur Extinction. Retrieved from National Geographic: http://science.nationalgeographic.com/science/prehistoric-world/dinosaur-extinction/

Patranek, S. (2002, February). 10 ways the world could end. 10 ways the world could end. Retrieved September 20, 2015, from https://www.ted.com/talks/stephen_petranek_counts_down_to_armageddon#t-1716708

Smith, D. (2005, September 28). What killed the Dinosaurs? Retrieved from DinoBuzz: http://www.ucmp.berkeley.edu/diapsids/extinctheory.html

The Department of Paleobiology. (n.d.). Extinction of the Dinosaurs. Retrieved from Geologic Time: http://paleobiology.si.edu/geotime/main/htmlversion/cretaceous4.html

The Harelip Sucker Fish

The Harelip sucker fish was reported to be common in North America during the late 1800’s. It was thought to have been between 12-18 inches long, with thin lips and few taste buds. Its characteristics indicate that it most likely tracked down food through sight. It had a very restricted habitat which was deep pools between shoal areas with extremely clear water in order to sight its prey - snails, limpets, fingernail clams and small crustaceans (Kaufman & Mallory, 1993). The last sighting of the fish was in 1893 and is thought to have become extinct in the early 1900’s. The Harelip Sucker were widespread at a time where humans were trawling on a commercial level, however the fish was not hunted to extinction. Its extinction was an indirect consequence of human actions, however the direct cause of the death was starvation (Miller, Williams, & Williams, 1989).

The decline in Harelip Sucker fish was due to the agricultural practises on land increasing sediment input and in turn, increasing the turbidity currents, lowering the visibility in the area. The Harelip Sucker was a visual feeder which used sight to identify its prey, and therefore the increase in turbidity made it impossible to feed. It is also thought that the increase in pollution and siltation from the agricultural practises may have actually declined the numbers of snails and other food sources, limiting the food sources for the fish (Kaufman & Mallory, 1993).

Although its extinction was a result of agricultural practises, if we view this as a disturbance to the system, the underlying factor of the extinction was starvation. The disturbance to the system meant that its food source became scarce and it no longer had the ability to find its food due to its specific build. This can easily be related to humans. A disturbance to our system could easily impact our food sources. We are fortunate that our food sources are so widely spread that small changes in the weather system don’t have an impact globally. We are able to transport food from region to region what seems almost effortlessly when we can buy what we want from our supermarket shelves. While small events such as hurricanes can effect local scale food sources detrimentally, something like a large volcanic eruption could have a huge effect on the growth of crops. Events like this on a large enough scale could definitely have a detrimental effect to how humans source food. Not to mention the crops being effected, but the ways in which we transport food would be extremely affected also. It is human’s responsibility to build resilience against these events – ensuring that we can locally source food, and source enough to feed our communities.

References

Kaufman, L., & Mallory, K. (1993). The Last Extinction. USA: Massachusetts Institute of Technology.

Miller, R., Williams, J. D., & Williams, J. (1989). Extinctions of North American Fishes During the Last Century. Fisheries, 22-38.

The Golden Toad

The Golden Toad have become extinct only recently, however they did not go extinct as a result of poaching or hunting by humans. It is most likely that their extinction is due to change in the climate. The Golden Toad was observed meeting annually in groups over 1500 to mate from at least 1972 when at a preserve discovered in Monteverde, Costa Rica. Scientists were able to observe the Golden Toad annually during these meetings, however in 1988 and 1989, only one toad appeared at the sight and a few more 4km South East. Then, in the years following, no toads were to be found at any location. They are classed as extinct as there have been no sightings of the Golden Toad since the late 80’s (Pounds & Crump, 1994). That is an extremely quick decline in numbers, from finding over 1500 toads in a single spot one year then none only a few years later means that an event or a rapid change in climate has affected the adults of the population significantly for them to not be returning to breed.

The Golden Toad

Photo Source: http://www.bagheera.com/inthewild/van_anim_gldtoad.htm

There are several hypotheses as to what happened to the Golden Toad. Some believe that they are hiding in reserves waiting for a change in climate to mate again (Crump, Hensley, & Clark, 1992), however this hypothesis is believed to be invalid due to the fact that the life span of the golden toad averages around 10-12 years, impossible for them to be still hiding due to the fact their last appearance was in 1989 (Pounds & Crump, 1994).

Amphibians vary in the ways in which they hydrate, however it is most common for toads to hydrate by absorbing moisture through their skin. They are often observed laying on wet surfaces such as wet rocks, logs and soil. The way for them to control their body temperature is through evaporative cooling, resulting in them losing water. Groundwater sources are the most common source for the toad to hydrate from, as their permeable skin allows them to hydrate from soil and tree roots. However the amount of ground water in a region is highly dependent on the seasons’ temperature and the amount of precipitation (Pounds & Crump, 1994).

El Nino came into play over Costa Rica in 1986-1987 which lasted a whole July-June cycle. All over the Monteverde region, El Nino affected the precipitation levels to be at an all-time low, and in turn a record low of stream discharge. In comparison to the 1982-83 El Nino, this one had unusually low precipitation levels. The seasons of the year in which the toads depended on for precipitation were very weak, and the dry season was extremely harsh, and furthermore, the temperature did not decrease after (Zhang & Endoh, 1994). Data gathered suggested also that at the time in the year when streams were being replenished, the groundwater level was continuing to drop. The warm, dry environment of meant that the breeding pools were dried up, and as a result the eggs and tadpoles all died (Pounds & Crump, 1994). The non-return of the toads the following year however is not dependent fully on the death of the young as proved by their average life span being around 10-12 years.

It is thought to most likely be the dehydration which was the main cause of the extinction, but there are several other hypotheses such as acidification of waterways due to human activity – although the pH of the waterways did not change dramatically throughout that period, human activity is not ruled out. Parasites are also a possibility as they have been the cause of extinction to many other amphibian species (Pounds & Crump, 1994). These hypotheses however are yet to be fully investigated.

The extinction of the Golden Toad goes to show how much the weather system can change over a short period. In this instance, should the hypothesis that dehydration was the main cause of extinction, it goes to show how weather can rapidly effect important resources. In the case of the Golden Toad, this resource is water. In the case of humans, the resources we need to survive are food and water, two resources which are extremely easily influenced by the climate. We are lucky in the sense that we have technology able to access water and alter it for us to consume. However as temperatures rise, the environment in which crops are growing is forever changing. The soil is being damaged, becoming less and less resourceful. While in other cases which I have investigated, the main cause of extinction was the lack of ability to adapt to an environment, the main issue here was the change in the amount of crucial resource – water. Humans should be concerned about the rise in temperature and how this is affecting the resources we need in which to survive. Not only are we dealing with the population nearing carrying capacity, we are also being faced with the issue of vegetation not being able to grow in locations they used to as a result of the temperature rising and effecting soils and on top of that, water limitations.  

References

Crump, M. L., Hensley, F., & Clark, K. (1992). Apparent Decline of the Golden Toad: Underground or Extinct? N/A: American Society of Ichthyologists and Herpetologists (ASIH).

Pounds, J., & Crump, M. (1994). Amphibian Declines and Climate Disturbance: The Case of the Golden Toad and the Harlequin. N/A: Blackwell Publishing for Society of Conservation Biology.

Zhang, R.-H., & Endoh, M. (1994). Simulation of the 1986–1987 El Niño and 1988 La Niña events with a free surface tropical Pacific Ocean general circulation model. Journal of Geophysical Research, 7743–7759.

Placoderms

Picture source: http://www.devoniantimes.org/who/pages/phyllolepis.html

The Placoderms were the most diverse and successful group of fish in the Devonian period (420-360 Mya). Placoderms were aquatic vertebrates, which had characteristic platy armour. Their habitat varied extremely, being found from the Arctic to the Antarctic, high altitudes in lakes, and depths around 3km deep in the ocean, found in both marine and non-marine settings. There were nine subgroups, all evolving at different periods of the Devonian, however no subgroups survived through the Devonian Carboniferous extinction (Young, 2010).

The Hangenberg event took place at the late Devonian period. It was this event in which the Placoderms became extinct. The several events which happened in the late Devonian affected 70% of marine life, however terrestrial species were hardly affected (Bond & Wignall, 2008).

The exact cause of the event is yet to be proved, however there are several hypotheses which are commonly argued amongst scientists. The most viable hypotheses focus on the idea that the spread of terrestrial plants (Murphy, 2005). The increase in terrestrial vegetation meant that more organic material and nutrients were being deposited into waters, causing the waters to become Eutrophic (nutrient rich) (McGhee, 2012).  

Eutrophication process.

 Diagram source: https://sites.google.com/a/owu.edu/lake-erie-eutrophication/what-is-eutrophication/the-nutrients

Eutrophication occurs as a result of a water body becoming enriched in nutrients, enhancing photosynthesis in the shallow waters through the formation of algae blooms, however creating anoxic waters at the bottom of the water body as a result of decomposition taking place. In addition to the eutrophication of shallow tropical waters, wide spread forests speed up the process of soil formation, and in addition, also sped up silicate-carbonate cycle. The process as a whole consumes CO2 and releases it in the form of dissolved silicate rocks into oceans in which it the precipitates and forms marine sediments.  The transferring of CO2 from the atmosphere to the hydrosphere meant that there was loss of a greenhouse gas, and therefore resulted in cooling (Bond & Wignall, 2008).

In short, the terrestrial widespread of plants and forests resulted in reduction of CO2 in the atmosphere, and lead to a global cooling event. Eutrophication would be a viable hypothesis as to how bottom dwelling species in the tropics became extinct – they could not survive in the anoxic conditions (McGhee, 2012). Global cooling resulting in a short glaciation may be to blame to for the extinction of the remainder species which lived at the poles – particularly the South Pole where ice caps rapidly formed. While there is no extensive evidence for a glaciation event in terms of a sedimentary deposit, the sudden drop in sea level and temperature indicates it was highly possible (Bond & Wignall, 2008).

To compare the extinction of Placoderms to Humans is extremely difficult. The extinction of the species was the result of climatic and atmospheric changes due to the widespread of terrestrial plants. The short term prediction for climate in our lifetime is for it to continue to increase, and seeing as we are coming out of a glacial event, cooling and glaciation is one thing we won’t have to worry about. However adjusting to a new climate is something we should be concerned about considering how fast our global temperature on average is increasing, and should the rapid glaciations be the sole reason which caused the extinction of the Placoderms, then the need to rapid adapt to a new climate should be a concern for humans in the future.

References

Bond, D., & Wignall, P. (2008). The role of sea-level change and marine anoxia in the Frasnian–Famennian. Palaeogeography, Palaeoclimatology, Palaeoecology, 107-118.

McGhee, G. (2012). Extinction: Late Devonian Mass Extinction. Chichester: John Wiley & Sons Ltd.

Murphy, D. (2005, July 9). Late Devonian Mass Extinctions. Retrieved from Devonian Times: http://www.devoniantimes.org/opportunity/massExtinction.html

Young, G. (2010). Placoderms (Armored Fish): Dominant Vertebrates of the Devonian Period. The Annual Review of Earth and Planetary Sciences , 523-550.