It’s Happening: The Cost of Convenience
Chapter 5: Extinction
It’s happening.
If you looked out your window right now, it is most likely that there are no triceratopses walking
around. If there is you should probably consult someone if you do see one. Something must have
happened to the dinosaurs, considering that they do not live on the Earth anymore. The triceratops, and
all the other dinosaurs for that matter, went through extinction. Extinction is defined as “The death of an
entire species or population”. When asked specifically about the extinctions, many people think of a single,
catastrophic event that wiped out nearly all life on earth and brought in a new generation of species. In
truth, the extinction that killed the dinosaurs was not the only large-scale extinction event. Rather,
throughout millions of years there have been multiple mass extinction events that have each killed off the
majority of species on the earth. In fact, we now know of 5 great extinction events. While these events
happened over hundreds of thousands of years, humans have the potential to cause such an event through
the staggering impacts of climate change and human environmental interaction. In this chapter, we will go
over the history of extinction, and how such events occur. We will also observe how extinctions affect
both humans and natural ecosystems, and how extinctions are affected by climate change.
Figure 1: A depiction of how the dinosaur extinction looked.
Processes of Extinction
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As mentioned previously, some extinctions happen over long periods of time, though some may
occur more rapidly. Many extinctions occur in isolation when an ecosystem changes so it can no longer
support a species. In other cases, extinctions that happen over long periods of time and wipe out most of the life on
Earth are called “Mass extinctions”. It should be noted that isolated extinctions are not mutually exclusive
with mass extinctions. Remember that despite the severity of mass extinctions, such events still often
occur over thousands of years. As such, individual extinctions can cause chain reactions of extinctions that
contribute to mass extinctions. In this chapter, we will discuss extinction both in terms of individual
extinctions and mass extinctions. We will also discuss how individual extinctions contribute to mass
extinctions.
Individual Extinctions
Individual Extinctions can occur in one of two ways: a species can go extinct by losing its “niche” in
an ecosystem, or by becoming the victim of excess predation. It is well known in biology that organisms
must fulfill a unique role, or niche in an ecosystem to survive. If two species occupy the same niche, the
one is doomed to eventually go extinct. Normally, a species’ population is kept at a stable equilibrium in an
ecosystem. If a species’ population drops to low, the predator species’ population will drop as well to
compensate. This ensures the stability and survival of species. However, if two species occupy the same
niche, this stability is lost. Imagine that Species A and Species B survive in the same climate, eat the same
plants and are hunted by the same predators. The only difference is that species A reproduces 10% faster
than species B.
Mass Extinctions
As mentioned before, there have been five mass extinctions in Earth’s history: the OrdovicianSilurian, the Late Devonian, the Permian, the Triassic-Jurassic, and the Cretaceous-Tertiary (also known as
the K-T extinction).\Many of these extinction events had a
catastrophic original cause. For instance, asteroid impact and
oxygenation have both caused mass extinctions. However, an
equally important concept of mass extinctions is the concept of
chain reactions in extinctions. Some species, called Keystone
Species, are very important to the wellbeing of entire
ecosystems. For instance, Salmon in northern streams are
keystone species. Not only do they feed animals such as bears,
they also provide absolutely vital nutrients such as nitrogen
from the sea to forested ecosystems. Chain Extinctions may
not be enough to cause a Mass extinction on their own, but
Figure 2: A graph of Number of
Families vs. Geological Time,
they can easily exacerbate the effects of other catastrophic
showing the five major extinctions.
events to the extent that mass extinctions are caused. See the
YouTube video on the wiki to find out more about the five major mass extinctions.
It’s Happening: The Cost of Convenience
What does this have to do with Climate Change?
Figure 3: A sculpture of a rabbit in a gas mask.
Now this textbook is about Climate Change, and we have not discussed Climate Change much in
this chapter. Climate Change is a driver of both single extinctions and mass extinctions. It has effects on
ecosystems, such as flooding due to rising sea levels. A single ecosystem could be changed to where it can
no longer support a certain species. As an example, let’s use a Canadian Lynx. The rising temperatures in
Canada due to Climate Change cause the snow to melt. Different subgroups of Canadian Lynx’s paws are
adapted for running on different types of snow depending on the region. It enables them to hunt
snowshoe hares in different areas of their natural habitat. Since the rise in temperature is causing the type
of snow to become crustier, the subgroups with foot adaptations not for running on crusty snow only
have three options: move, adapt, or go extinct. Moving and adapting have already been discussed in this
book, so see the previous chapters for more information. Let’s say the temperature change is moving too
fast for the species to adapt and there are lakes blocking the path of the Canadian Lynx. This means that
extinction is the only option. As shown single ecosystems and organisms are affected by climate change,
but the biome as a whole is also affected. Climate Change could be considered a “catastrophic event”,
killing high percentages of Earth’s Species. It may have happened in the past. Scientists theorize that the
Permian Extinction Event was caused by volcanic eruptions coating the sky with volcanic gases, leading to
a drop in temperature around the world and killing most of the marine life. It is also believed that Climate
Change could case the sixth known mass extinction, which could be happening right now.
Effects of Extinction on Humans
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In some cases, extinction seems to
benefit humans. For example, life on Earth
would be very different if Haast’s eagle was
still alive. Haast’s Eagle was a large raptor
with a wingspan of up to three meters. It
preyed on moa, which more than twice its
size. It would probably prey on children
nowadays. Even though there are positive
effects, extinction has and will have severe
negative impact on humans. One of the main
reasons is the loss of biodiversity. Biodiversity
is defined as the variety of life on earth. It is
important because as mentioned previously, if
Figure 4: Haast’s Eagle hunting moa
one organism dies the whole ecosystem could
go down. Biodiversity also provides a wide
range of biological resources to develop new medicines and creates a wider range of life for research. 640
billion dollars are in the market for pharmaceuticals based off of biodiversity, and that is not even
including the market for biotechnology. Once certain species are gone, we as a human race will never gain
the benefits. Also, we rely on plants to provide oxygen, and certain plants and animals for food. We need a
variety of crops to grow in different conditions to survive. If they are gone, we as a species might go
extinct.
Human Efforts to stop Extinction
It’s Happening: The Cost of Convenience
Despite humans being the cause of much extinction through hunting, destruction of habitats,
pollution, and climate change, there are many efforts to try to save and conserve species. As mentioned in
a case study in the decline of Amphibian populations and extinction, one of the more important things
that we as humans do is classify
how much danger a species is
of becoming extinct. The
classification of species is called
the IUCN Red List of
Threatened Species. This way
the proper resources can be
given to the species that need it
most. The data on the wiki
shows how the status of
different species fluctuates on
the list. Some of the changes
are due to population changes,
and some are due to having
better information about the
population. There is an overall
Figure 5: The IUCN ranking of species endangerment
increase in numbers through all
of the populations due to those
two factors. Humans are also trying to use breeding programs and zoos to bring populations back from
the brink of extinction. An example is the California least tern. It is a type of bird that was first hunted for
its feathers, and then went towards the brink of extinction for unknown reasons. In 1970 there were only
225 nesting tern pairs found in California. After predator regulation and beach protection programs, the
population increased to 6,568 birds in 2006. More ways to stop extinction includes raising money for
conservation efforts and cutting down on hunting, pesticide use, and habitat destruction. There are even
efforts to bring back extinct species, such as sequencing genomes to possibly clone species. Read the full
case study on the wiki to find out more about conservation efforts for amphibians. All of these things
help, but since climate change is one of the main reasons for extinction; possibly one of the best ways for
humans to stop extinction is to stop causing climate change.
Note: The data, video, lab, and model are on the wiki.
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Glossary
Extinction-The death of an entire species or population
Mass Extinction-extinctions that happen over long periods of time and wipe out most of the life on Earth
Keystone Species-species that are necessary to the structure of an ecosystem
Biodiversity-the variety of organisms in a certain area
Citations for photos in order:
Arnold, Peter. Triceratops and Tyrannosaurus Rex. Digital Image. Mass Extinctions:What Causes Animal Die-Offs.
National Geographic. Web. 18 May 2014.
Raup, David M., and J. John Sepkoski, Jr. 1982. "Mass Extinctions in the Marine Fossil Record," Science
215:1501-03.
Macdowell, Kate. Rabbit with Gas Mask. Digital Image. Scribol Art and Design. 28 May 2011. Web. 18 May
2014.
Megahan, John. A Haast’s Eagle Attacks A Pair of Moa. Digital Image. New Zealand’s Long-Lost Giant Raptor.
National Geographic. Web. 16 May 2014.
Red List Structure of Categories. Digital Image. IUCN Red List Criteria for Endangered. The Encyclopedia of
Earth. 12 October 2009. Web. 18 May 2014.
Citation for Case Study
Croteau, Emily, and Cy L. Mott. "Saving Endangered Species: A Case Study Using Global Amphibian
Declines." Knowledge Project. The Nature Education, 2011. Web. 20 May 2014.
Citation for Data
“Table 2: Changes in numbers of species in the threatened categories (CR, EN, VU)
from 1996 to 2013 (IUCN Red List version 2013.2) for the major taxonomic groups on
the Red List)”. IUCN Red List Version. 2013.
<http://cmsdocs.s3.amazonaws.com/summarystats/2013_2_RL_Stats_Table2.pdf>.
Citation for Video
It’s Happening: The Cost of Convenience
SciShow. “Mass Extinctions.” YouTube. 21 May 2012. Web. 18 May 2014.
Citations for Sources and Suggested Reading
"110 Success Stories for Endangered Species Day." On Time, On Target. Center of Biological Diversity,
2012. Web. 19 May 2014.
Di Silvestro, Roger. "Can Lynx Survive Global Warming?" National Wildlife. National Wildlife Federation,
1 Dec. 2004. Web. 19 May 2014.
"extinction." Dictionary.com Unabridged. Random House, Inc. 20 May. 2014.
Hoffman, Hillel J. "The Permian Extinction—When Life Nearly Came to an End." National Geographic.
Web. 19 May 2014.
Kolbert, Elizabeth. The Sixth Extinction. New York: Henry Holt, 2014. Print.
Maas, P.H.J. Stop Extinction! How Can You Help?, The Sixth Extinction Website.
<http://www.petermaas.nl/extinct>. Web. 19 May 2014.
"Mass extinction." The American Heritage® New Dictionary of Cultural Literacy, Third Edition. Houghton Mifflin
Company, 2005. 20 May. 2014.
Shah, Anup. "Why Is Biodiversity Important? Who Cares?" Global Issues. 19 Jan. 2014. Web. 19 May 2014.
Switek, Brian. "New Zealand's Long-Lost Giant Raptor." Phenomena. National Geographic, 21 Dec. 2012.
Web. 18 May 2014.
"Why Do We Care About Endangered Species in North Carolina?" North Carolina Ecological Services. U.S
Fish & Wildlife Service. Web. 19 May 2014.
Citation for Picture on Wiki
http://www.yenra.com/dodo-bird/
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