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EXAMPLAR – OPINION PIECE
LEVEL 4
The Value of Wolves
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When Yellowstone National Park was first established in 1872, many grey wolves
lived in the park. Starting in the early 1900’s, people began to kill these animals for their
furs, and to protect cattle and other farm animals. In 1926, the last wolf was killed in
Yellowstone National Park. By 1970, environmentalists began to notice a change in the
ecosystem of the park. They then reintroduced 15 grey wolves from Canada to the park.
Many of the farmers believe that this was a poor decision because they knew that their
livestock was at risk for being killed. On the contrary, many environmentalists think that
this was the right choice. It was necessary to reintroduce wolves to Yellowstone National
Park because of the animals and plants that were being harmed, and the results on Isle
Royale when the same situation occurred there.
The wolf is known as a ‘keystone species’. This means that they are a vital animal in
the food chain. For example, the leftovers that wolves eat provide a quick meal for
scavengers such as ravens, eagles, magpies and bears. In the winter, it is critical for
wolves kill their prey and leave leftovers, as this is the main source of food for these
animals (Hayes, et. al., 2000). There has been known to have been up to 135 ravens feast
off of one wolf kill (Stahler, et. al., 2002). Without the wolf, the number of ravens started
to decrease in the park. In addition, the number of weasels and badgers increased
dramatically, while the number of fishers, bobcats, lynx, and red foxes dropped (Smith et
al., 2003). The animals that were affected the most by the lack of wolves were the
ungulates; the primary food source for wolves. The number of these animals, especially
elk, increased dramatically when the wolves were gone. As elk consist of 92% of a wolf’s
diet (Mech, et. al., 2001), once they were reintroduced, scientists from the university of
Wyoming predicted that the elk populations would increase by 15% to 25%. Other
predators of elk are cougars, grizzly bears and black bears. Before the reintroduction of
the wolf in Yellowstone National Park the number of cougar kills towards elk was twice
the amount as it was after (Crabtree and Sheldon, 1999). Also, since the reintroduction of
the wolves, 4 beaver colonies have been established in the Yellowstone area (Tyers, et.
al., 2000). As stated, many species have benefited from the reintroduction of wolves and
therefore, the choice to reintroduce wolves was a positive one for the food chain and
ecosystem of Yellowstone National Park.
Plants were greatly affected by the absence of the wolf. Ungulates are herbivores, as
they feed off of plants. When the wolves were not in Yellowstone National Park, the
population elk and other ungulates increase, as the number of willows and other plants
decreased (Ives. 2004). Cottonwood trees are food for elk, and they are vital to rebalance
stream ecosystems. The reintroduction of wolves tremendously impacted the quality of
the streams in a positive fashion, and they prevented the extinction of the Cottonwood
tree (Science Daily, 2003). Other plants in the stream ecosystem such as berry-producing
shrubs suffered when the wolves were not present. Their population decreased and
negatively affected the birds, insects and fish in that area (Science Daily, 2003). Another
plant that was affected was the Aspen tree. In some areas, there was up to a 90% decrease
of this tree (Ripple, et. al., 2001). Once wolves were present again, these plants could
multiply and grow taller, and this created a more balanced environment. The soil became
healthier and had more nutrients as many coniferous and deciduous trees had been
affected. These plants and trees are important for many species of birds, mammals,
beavers and moose. Due to the necessity for plants in to have a balanced ecosystem,
wolves play a large and positive role in Yellowstone National Park.
Isle Royale is an island that is completely isolated and the animals their have no way
of swimming to the shoreline of another land mass. On this island there is an ecosystem
of plants and animals, including wolves. At one time wolves were completely wiped out
and the island suffered greatly (Smith, et. al., 2003). There are some differences between
these two ecosystems. Isle Royal is a closed system (the wildlife is unable to move tom
difference areas to live), and it has about one third of the number of animals at
Yellowstone National Park. Yellowstone is an open system and they have a wider
variety if animals. The affects of no wolves on Isle Royale is much greater and it is a
good spot to see the affects with the lack of these animals (Haines, 1997). When there
were no more wolves in Isle Royale, the ungulate species greatly increases as well as the
plant species. (Allen 1979). In this case, wolves reintroduced themselves by crossing
Lake Superior in the 1940’s (Allen, 1979). The wolves helped with keeping the food
chain balanced, and they allowed the forest to recover from moose grazing. Although this
reintroduction helped, there are still many negative affects from when wolves were not
present. Since the many of the trees were not able to escape moose feedings, many of
these trees have still not been able to grow back (McLaren and Janke, 1996). Even after a
century has past, the forest at Isle Royale is not what it used to be. This would have been
similar results to Yellowstone National Park.
There are several reasons why the reintroduction of wolves was necessary for
Yellowstone National Park. The plant and animals were suffering greatly without their
presents. Also, the devastating affects of a similar situation on Isle Royale caused
concern, and showed the “cause and effects” for Yellowstone. Clearly, bring these
animals back to Yellowstone caused many positive effects. As of 2002, there were 14
packs (132 wolves) in Yellowstone (Boyce, 1993, Mack and Singer 1993). Considering
the above reasons, it has been shown that there should be a greater knowledge and
appreciation for the value of wolves.
Bibliography
Allen, D.L. 1979. The wolves of Minong; Their vital role in a wild community. Houghton Mifflin
Company, Boston. 499 pp.
Boyce, M.S. 1993. Predicting the consequences of wolf recovery to ungulates in Yellowstone
National Park. Pages 234-269 (In) Cook, R.S., (ed.) 1993. Ecological issues on
reintroducing wolves into Yellowstone National Park. Scientific Monograph NPS/
NRYELL /NRSM-93/22, USDI Nat. Park Serv., Denver, Colo. 328 pp.
Crabtree, R.L. and J.W. Sheldon. 1999. Coyotes and canid coexistence. Pages 127-163 (In) Clark,
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