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ECOLOGY
A New View of Species Extinction
Comparing the Value of Two Marine Mammal Species
Kali Pruss ‘14
W
e all hear about climate
change, species extinction,
and impending environmental collapse. We see commercials, books,
and films dedicated to inspiring action
to save endangered species. However,
species preservation is not as simple as
human goodwill – investing in saving
a species is an economic investment as
well. With the number of endangered
species climbing each year, it is not
economically plausible to pour money
into saving every single endangered
species (1). Many intelligent mammal
species receive more attention than
declining plant or insect species. For
example, whales have a “unique place
in conservation lore” – they have become a symbol of humanity’s capacity
for greedy overharvest (2). People also
simply find them fascinating; whales
have become the subject of successful
commercial movies, such as Free Willy,
and literature, such as Moby Dick. We
speak of “saving the whales”, but is it
reasonable to attempt to do so? Given
two marine mammal species, would
one be more valuable to save? Based
on ecologic, economic, and intrinsic
value and the potential for reestablishment, would killer whales or blue
whales be more worthwhile to sustain?
We may ask, “What difference will
it make if sharks or whales disappear?”
It is estimated that the ocean holds ten
million species–what’s the big deal
with losing one or two (3)? Some scientists believe that “many species, perhaps most, do not seem to have any
conventional value at all, even hidden
conventional value” (4). Others think
that biological diversity, the number,
variety and variability of living organisms in a given assemblage is the key
to life as we know it and “holds the
world steady” (3, 5). Whales are some
of the most voracious consumers in the
oceans due to their great abundance
and their large metabolic demands;
thus, they have the potential to play an
ecologically significant role in marine
ecosystems as important consumers in
food webs. Additionally, their carcasses can support more than 350 species
for 80 years (2). However, in his book
The Future of Life, Wilson argues that
every time humanity entered a virgin
environment, most of the megafauna
soon vanished (6). Humans routinely
eat their way down the food chain: Native Americans quickly hunted North
America’s largest mammals, such as
the Wooly Mammoth and the Giant
Sloth, to extinction. If megafauna vanish often, would the disappearance of
whales, or one species of whale, matter?
What are the ecological impacts of killer
whales and blue whales independently?
Killer whales have a large impact on their ecosystems. Bioenergetic analyses have been used to assess the caloric needs of average-sized
whales. A 2,800-kilogram female requires 193,000 kilocalories per day; a
4,733-kilogram male requires 287,000
Image courtesy of Peter Nijenhuis.
Orcas, also known as killer whales, play an important in eco-tourism and the entertainment industry as the symbol of SeaWorld’s “Shamu” business.
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Fig. 1: A simplified version of the Antarctic food chain. Krill provides the basic resource for many
large mammals (10).
kilocalories per day (2). Because orcas
are top predators in the food chain,
a cascade of effects may reverberate
through their ecosystem, often negatively impacting the species below
them. One example of this is from hunting of whales in Western Alaska, which
led to orcas switching their primary
prey to sea otters. Increased predation
by killer whales led to decline in sea otter populations (2). Sea otters feed on
sea urchins, so the urchin population
exploded with increased killer whale
predation. The increased sea urchin
populations have deforested many kelp
beds. The otter’s key role in the ecosystem was essentially eliminated by
killer whale predation (7). Kelp forests
are one of the most diverse and productive ecosystems in the world, and
deforestation has profound and lasting
impacts on many species (7, 8). Whale
hunting led to killer whales having a
negative impact on their ecosystems.
Blue whales, on the other hand,
have a less dramatic impact on their
ecosystems. The largest animal on
the planet, blue whales also have high
metabolic demands. Blue whales require between four and eight tons of
food per day (9). However, blue whales
feed almost exclusively on krill, a small
shrimp-like invertebrate. Krill abundance is crucial to blue whale populations. However, many other whale species also feed on krill as their main food
resource (10). As other whale populations increase, krill population levels
decrease, and as krill abundance decreases, blue whales may suffer. Commercial fleets also harvest krill and
may also compete with blue whales for
the resource (10). However, because
FALL 2011
krill is widely abundant and has a relatively stable population, a decrease or
increase in blue whale population will
have relatively little effect on krill populations and the ecosystem as a whole.
Krill have more predators than just
blue whales, as shown in Fig. 1. The size
of blue whale populations affects krill
population sizes less than vice versa.
Similar to the debated importance
of biodiversity in terms of the health of
ecosystems, the economic value of biodiversity is controversial. Many argue
that a true value cannot be placed on
the worth of biodiversity. Other economists calculate the total value of a species as the components that arise from
current use and expected future use (4).
“Use” may be commercial or noncommercial, such as the need for raw materials, aesthetic satisfaction or personal
experiences. Determining the economic value of a species is anthropocentric
because humans assign the values of
what is “worthwhile” and utilitarian
because different characteristics of a
species count to the extent that people
want them to (4). Whales may be economically valuable in many ways. Tourist activities, such as whale watching,
yield high revenue in many countries.
Countries around the world that have
invested in whale watching currently
host 13 million whale-watchers per year
(11). Starting whale-watching industries in countries that do not yet have
them could generate an additional 413
million dollars and 5,700 jobs. Doing
so would increase total benefits from
whale-watching to over 2.5 billion dollars per year at 19,000 jobs globally (11).
Killer whales are important in
eco-tourism and the entertainment
industry. Every year, thousands of
people travel to the Pacific North Coast
Integrated Management Area (PNCIMA) for opportunities to see orcas in
the wild. The overall economic value
of killer whales to the whale watching industry is millions of dollars
per year (12). Expenditures per person per day on eco-tourism for killer
whales were 472 dollars in 1986 and
530 dollars in 1989 (13). SeaWorld
has turned the killer whale image into
a multi-million dollar brand. “Shamu”
is SeaWorld’s largest business and
the company owns more killer whales
than anyone else in the world (14).
Blue whales yield less annual revenue than killer whales. Expenditures
per person per day on eco-tourism for
blue whales in 1986 and 1989 were only
between 62.50 and 70.40 dollars (13).
Blue whales are not used in the entertainment industry and are the subject
of fewer whale-watching expeditions
due to their lower densities than orcas.
In his 1973 paper “Profit Maximization
and the Extinction of Animal Species,”
Colin Clark argues in favor of the economic value of the total extermination
of blue whales (16). In historical human
exploitations of various populations,
Clark points out that a characteristic
pattern occurs. As harvests expand, exploitation increases, fears are expressed
for the survival of the population and
associated industry, and conservation
measures are considered, and sometimes implemented. However, it is a
reasonable possibility that the owner
of a resource would want to maximize
the present value of harvest (and discount the future revenues by doing so).
According to Clark, it is economically
preferable to kill every blue whale in
the ocean and to reinvest the profits
in growing industries rather than wait
for the long-lived species to recover to
the point of sustainable annual harvest.
It is impossible to assign a true
value to the intrinsic worth of a species
but still important to consider when
determining a species’ worth. According to Earle, most people feel immense
goodwill toward dolphins, whales, and
other marine mammals (3). The high
revenue that comes from killer whale
eco-tourism is a result of the powerful
aesthetic and intrinsic value humans
hold for killer whales (12). Humans value orcas’ social behavior, intelligence,
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and strength (12). Killer whales are
highly protective of their young, and
other adolescent females in a pod often assist mothers with infant care (9).
Killer whales are the largest of the dolphins and are one of the world’s most
powerful predators. Our fascination
with these creatures is evident in our
portrayal of them in literature throughout history: killer whales have been
the subject of ancient mythological
stories and current popular films as vicious monsters or as man’s best friend.
Humans value blue whales for different reasons than they value orcas.
Blue whales are the largest animals to
ever inhabit the earth. They are as long
as approximately three school buses
(70 to 90 feet) and weigh between 200
and 300 thousand pounds. The blue
whale has a heart the size of a small car
and a tongue that weighs as much as an
elephant (9, 15). These creatures leave
us in awe. However, we know relatively
little about blue whales. Unlike killer
whales, they usually travel alone or in
pairs and can hear each other from up
to 1,000 miles away (9). Their relatively low densities make it difficult
for researchers to learn about their
migration patterns and life histories.
Blue whales not only represent a marvel as the world’s largest animal, but
also present a potentially interesting or
important opportunity to learn more
about ocean organisms and ecosystems.
Killer whales have never been
hunted extensively by humans and as
of yet are not considered “endangered”,
but “threatened” (9). Second to humans, they are the most widely distributed species in the world (17). They are
not restricted to specific regions, a frequent characteristic of endangered species. Minimum worldwide abundance
estimates of killer whales are around
50,000 individuals (2). Blue whales, on
the other hand, are a highly endangered
species. Their numbers have dropped
significantly due primarily to whaling
in the 20th century. Of the 5,000 blue
whales which inhabited the North Pacific, only 1,200 are left; only a few hundred reside in the North Atlantic, and
of the 20,000 blue whales in the Southern Hemisphere, only 9,000 remain,
half of which are pygmy blue whales
(18). Because of their “preciously low
numbers”, blue whales are especially
vulnerable to habitat degradation and
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reduction of their main food source,
krill. According to the Save the Whales
foundation, due to the amount of time
it takes for blue whales to grow and reproduce, it may be too late for their recovery despite all efforts to save them
(18). Moreover, many blue whales have
trouble finding mates due to their low
densities. Mori and Butterworth claim
that after their protection in Antarctica,
the blue whale population there experienced an 8 percent per year increase
(10). However, Save the Whales asserts
that even though a few populations are
increasing slightly, overall, their numbers are too small for recovery (19).
While blue whales are a biological
marvel and present possible research
opportunities, killer whales have a
greater economic benefit and will be
easier to sustain. The loss of blue whales
is likely to have relatively low ecological
impact, and they may be beyond saving
already. The already low economic revenue from blue whales would decrease
greatly from the amount of resources
that would be invested in the conservation of this species, as they may already be beyond saving. Although killer
whales currently have many negative
impacts on their ecosystems, humans
could potentially change killer whales’
primary prey again by trophic manipulation to benefit the ecosystem. For
example, since we know killer whales’
predation on otters caused the elimination of many kelp forests, introducing
a new source of prey for killer whales
could allow kelp forests to recover. Of
course, we do not truly face an ultimatum between these two species, and
Many would never advocate allowing
the extinction of blue whales. However,
this type of model can reveal a way of
thinking about conservation that more
traditional approaches would overlook.
Most conservationists only consider
each species’ intrinsic value and seek
to restore every species to a sustainable
abundance. While considering intrinsic
value is important, this approach may
not be practical. Taking a more holistic
view by considering the benefit a species
has to its ecosystem, to humans, and
the amount of human resources which
would be required for the species’ recovery may present a method which is
difficult to accept but most pragmatic.
References
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3. S. Earle, The World is Blue: How Our Fate
and the Ocean’s are One (National Geographic,
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