I will begin my research by
looking at the American Mastodon, a distant relative on the elephant and the
mammoth which took a widespread residency in North America around 125,000 years
ago. The mammal went extinct around 10,000 years ago, and while it is believed
that human influence and hunting would have been the final straw for the
extinction of the animal, the change in climate was hugely influential on
dwindling down the population years earlier (Zazula et al., 2014).
The American Mastodon was a
grazer which mainly fed off woody plants in coniferous and mixed woodlands. According
to the findings of the Mastodons bones in North America, they lived in high
latitudes (Zazula et al., 2014). Few remains are found in arctic/ sub-arctic
regions, however it is highly likely that they lived at very high latitudes
during interglacial periods when the temperature was warmer and the areas were
covered in woodlands. It coexisted with the mammoth, however they filled
different niches and were not fighting for the same resources, and therefore
their decline in numbers was not due to competition (Zazula et al., 2014).
Until a recent article published
in Proceedings of National Academy of Science in 2014, it was believed that
humans were responsible for the extinction of the species, however when
scientists re-dated the mastodon teeth, they dated back to millennia’s before
humans were even close to crossing over to America from Eurasia. Therefore if
there were no predators which could match the height and weight of the Mastodon,
or a predator that would match the skill set of a human, then it comes down to
the quick changes in climatic conditions which lead to the decline in numbers of
Mastodons (Zazula et al., 2014).
Artist interpretation of the American Mastodon by Stephen Moore
The most recent theory is that
the Mastodons decline was due to the species not being able to adapt to the
cooler temperatures from the Pliocene to the Pleistocene. During the warmer
periods of the Pliocene, the Mastodon would migrate north in latitudes to where
boreal forests were developing as opposed to the tundra landscape there is
today. The Mastodons could not migrate south fast enough to avoid to cooler
temperatures of the Pleistocene and the ice caps that developed with the
glacial period, and could not adapt quick enough to live in the cooler
temperatures (Zazula, et al., 2014).
The glacial period in the
Pleistocene was a result of the closing of the panama corridor, which had an effect
on the thermohaline circulations and thus contributed to a reorganisation of
the atmosphere as a result of change in the geology affecting the ocean
currents. The generation of more upwelling along coasts meant enhanced
productivity, however this also resulted in CO2 being drawn into the ocean
system and consequently furthering the cool down affect. Throughout the rest of
the Pliocene period there were warming and cooling events, leaving us humans to
live in an interglacial period today (Martínez-Botí, et al., 2015) .
The recent ice age that we have
come out of had average temperatures of 5-10C colder than today (Herring, 2012) . The Pliocene epoch
before that had temperatures relatively similar to today’s, meaning that the
change between the two epochs was fairly dramatic. However over the next 100
years it is predicted that the climate could increase by 1.1 to 5.4°C (Robinson, Dowsett, & Chandler, 2008) . The temperature
change over the next 100 years is half of the total change between two epochs –
which lasted hundreds of thousands of years. That means that over the course of
the next few hundred years our planet will undergo extreme changes which will
affect agriculture, water availability and many other necessities to human
life. The Mastodons declined significantly in numbers due to the extreme change
in climate and their inability to adapt. The optimist side of this is that
humans as a species have adapted from cooler temperatures to warmer
temperatures during their evolution throughout the Pleistocene epoch. However
it would be a matter of determining what temperature humans are capable of
adapting to in terms of a further temperature increase, and could agriculture
adapt simultaneously.
References
Herring, D.
(2012, March 5). Climate Change: Global Temperature Projections.
Retrieved from Climate: https://www.climate.gov/news-features/understanding-climate/climate-change-global-temperature-projections
Martínez-Botí,
M., Foster, G., Chalk, T., Rohling, E., Sexton, P., Lunt, D., . . . Schmidt,
D. (2015). Plio-Pleistocene climate sensitivity evaluated using
high-resolution CO2 records. Nature, 49-54.
Robinson, M.,
Dowsett, H., & Chandler, M. (2008). Pliocene Role in Assessing. EOS,
501-502.
Zazula, G., D. E.
MacPhee, R., Metcalfe, J., Reyes, A. V., & Brock, F. (2014). American
mastodon extirpation in the Arctic and Subarctic predates human colonization
and terminal Pleistocene climate change. Proceedings of the National
Acadamy of Sciences of the United States of America, 18460–18465.
