Biodiversity – What is it?
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Definitions
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Contraction of “biological diversity”
Fundamental unit = species
What is a species??
A group of genetically similar organisms that
interbreed naturally and freely to produce viable,
fertile offspring, but do not share this behavior and
outcome with individuals of other species
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Problem: Some people consider this definition to be
inadequate. Why??
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Some natural interbreeding between species
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Not all species distinct and static; hybrid swarms
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Some exchange of DNA without interbreeding
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Genetic polymorphism; species flocks
Biodiversity – What is it?
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Definitions
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Components
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a.
b.
c.
Term “biodiversity” often used incorrectly or
incompletely
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Not synonymous with “species diversity”
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Encompasses three measures
Species Diversity
1) Species richness – Total number of species
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Often cited incorrectly as “biodiversity”
2) Evenness – Proportions of species in a community
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More difficult to determine (requires more complete
survey)
Genetic Diversity – Variety of genotypes
Ecosystem Diversity – Variety of habitat types
Biodiversity – What is it?
•
Definitions
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Components
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a.
b.
c.
Term “biodiversity” often used incorrectly or
incompletely
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Not synonymous with “species diversity”
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Encompasses three measures
Species Diversity
1) Species richness – Total number of species
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Often cited incorrectly as “biodiversity”
2) Evenness – Proportions of species in a community
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More difficult to determine (requires more complete
survey)
Genetic Diversity – Variety of genotypes
Keystone Species
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Ex: Sea otters in kelp forests
Biodiversity – Estimation
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Estimates of Biodiversity
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Described species ~ 1.8 million
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Insects > 1,000,000 species
Plants > 290,000 species
Probably an underestimate
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Only ~11,000 species of bacteria
Less conspicuous species studied less often
Estimates range from 3 – 100 million
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Around 6200 new eukaryote species described each
year
Recent estimate ~ 8.75 million (Mora et al. 2011)
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Still doesn’t capture microbial diversity (could
exceed all other diversity combined)
Biases
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Splitting of taxa more common than lumping
Tendency to increase number of described species
Cryptic species
Biodiversity – Estimation
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Biodiversity Hotspots
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Myers – Up to 20% of the world’s plant
species and more than 20% of the animal
species are confined to 0.5% of the land
surface
Biodiversity Hotspot – Area with high degree
of
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Biodiversity
Endemism
Risk of habitat degradation/loss
Concept originally intended for tropical and
subtropical areas
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Endemism less prevalent in temperate and polar
regions
Biodiversity – Value
A.
Value to Humans
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Economic
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Ex – Lomborg: $3-33 trillion annually
Biodiversity loss could lead to removal of species that
benefit humans but aren’t currently known to do so
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Ex – Chapin et al. (2002) suggested increase in frequency of
Lyme disease during 20th century may have been related to
increase in abundance of tick-bearing mice (once controlled by
food competition with passenger pigeons)
Species extinction reduces potential pool of species
containing chemical compounds with pharmaceutical or
industrial applications
Problem – Benefits may not be obvious
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Difficult to convince people that it’s important to preserve
something with no immediately apparent value to them
Ex – Economic value of viral resistance added to commercial
strains of perennial corn through hybridization with teosinte
(Mexican wild grass) is ~ $230-300 million/year
Biodiversity – Value
B.
Ecosystem Value
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1.
Biodiversity can have large effects on ecosystem
stability and productivity
Benefits of biodiversity
a.
b.
c.
Productivity
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Halving species richness reduces productivity by
10-20% (Tilman)
Nutrient retention
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Loss of nutrients through leaching is reduced when
diversity is high
Ecosystem stability
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Ex – Higher diversity (unfertilized) plots of native
plant species maintained more biomass during
drought than lower diversity (fertilized) plots
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Ex – Higher diversity plots of native plant species
had greater resistance to fungal diseases, reduced
predation by herbivorous insects and reduced
invasion by weeds
Biodiversity – Value
B.
Ecosystem Value
2.
Considerations
a.
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b.
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Species richness vs. evenness
Simple species richness may be deceptive as an indicator of
biodiversity and ecosystem stability
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Evenness usually responds more rapidly to perturbation
than richness and may have important ecosystem
consequences
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Richness is typical focus of studies and policy decisions
Importance of individual species
Charismatic megafauna: What about non-charismatic species?
Different species affect ecosystems in different ways (keystone
species vs. non-keystone species)
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Ex – Sea otters/Sea urchins/Kelp forests in eastern Pacific
Ocean
Question: How many species are required to maintain “normal”
ecosystem function and stability?
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No magic number
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Losing one ant species in a tropical forest may have less
immediate impact than losing one species of fungus that
is crucial to nutrient cycling in the soil
Biodiversity – Factors
A.
Nutrient Availability
1.
Oligotrophic
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2.
Dominated by a few species able to survive on limited
nutrients
Low diversity, Low biomass
Mesotrophic
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3.
Support greater numbers of species
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Rapid colonizers held in check by nutrient limitation
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Less aggressive species capable of surviving
High diversity, Medium biomass
Eutrophic
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Dominated by a few species able to grow and/or
colonize rapidly with abundant nutrients
Low diversity, High biomass
Biodiversity – Factors
B.
Selective Mortality
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Predation
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Ex – Birds with colorful plumage
Ex – Sea urchins (sushi)
Species-specific diseases/pests
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Ex – Dutch elm disease
Ex – Bark beetles
Biodiversity – Factors
C.
Habitat Disturbance
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Non-selective habitat disturbance has
potential to increase diversity
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Prevents competitive exclusion
Intermediate disturbance  Maximum
diversity
Biodiversity – Factors
C.
Habitat Disturbance
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Fire and fire-dependent species
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Ex – Peter’s Mountain Mallow (Iliamna corei)
Discovered in 1927 (50 plants)
Endemic to meadow in western Virginia
1986 - Three plants remaining
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Not setting seed
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Listed as endangered
Research on seeds indicated importance of fire
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Cracks hard seed coat, aiding germination
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Removes competing vegetation
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Had been suppressed in the area
Controlled burns in 1992 and 1993 led to
appearance of 500+ seedlings
Biodiversity – Factors
D.
Habitat Fragmentation/Destruction
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Most significant factor causing species loss
Smaller habitats support fewer species and
smaller populations than large habitats
Population sizes tend to fluctuate more in
smaller habitats than large habitats
Reduced population  Lower genetic
diversity
Behavior of territorial species changes in
fragments
Fragments may not support self-sustaining
populations
• Mount Hood
National Forest,
Oregon
• Patches due to
timber removal
Biodiversity – Factors
D.
Habitat Fragmentation/Destruction
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Most significant factor causing species loss
Smaller habitats support fewer species and
smaller populations than large habitats
Population sizes tend to fluctuate more in
smaller habitats than large habitats
Reduced population  Lower genetic
diversity
Behavior of territorial species changes in
fragments
Fragments may not support self-sustaining
populations
Biodiversity – Factors
E.
Exotic Species
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Species invasions may profoundly affect
ecosystems
Detrimental exotic species usually are
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Superior competitors
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Ex – Argentine ants, starlings, zebra mussels
Effective predators
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Ex – Nile perch, mongeese
Biodiversity – Factors
E.
Exotic Species
1.
Zebra mussel
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Competitor in Great Lakes and elsewhere
Transported from Europe in ballast water
Fouling organism
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Restricts movement of water through intake
pipes
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Colonizes boat hulls, pier pilings, buoys, etc.
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Fouls other organisms (clams, mussels)
Filter feeder – removes larvae and particulate
material
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Outcompetes native shellfish species for food
and space
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Removes larvae from water
Biodiversity – Factors
E.
Exotic Species
2.
Mongoose
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3.
Predator in Hawaii
Introduced in 1883 to combat rat population
Prey on native birds
Lionfish
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Venomous predator
Introduced in Caribbean/W Atlantic ca. early/mid
1990’s
Preys on 65+ spp. of fishes
No natural predators
Nile perch – Lake Victoria
Argentine ants - California
Brown tree snake - Guam
Caulerpa taxifolia - California
How might we justify a particular
environmental ethic?
1. Anthropocentrism
2. Moral extentionism:
zoocentrism/sentientism/psychocentrism, and
biocentrism
3. Novel features or entirely new approach such as
ecocentrism
Albert Schweitzer (1875-1965)
Reverence for Life
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A predecessor to later biocentric environmental ethics.
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Life is good in itself, inspiring, and deserving of respect: “I am life
which wills to live, in the midst of life which wills to live.”
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Schweitzer’s reverence for life can be interpreted as an attitude,
moral virtue, or character trait—environmental virtue ethics.
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But Schweitzer seemed to regard reverence for life as reverence for
life in and of itself, akin to an ethical norm or rule. This, however,
leads to “Schweitzer’s paradox.”
“On Being Morally Considerable” (1978)
Kenneth Goodpaster
What makes something morally considerable?
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Animal ethics people correctly argue that it is arbitrary to stop at
something like rationality and that sentience is morally considerable
because, in part, rationality presumes sentience.
But why stop at sentience?
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Sentience presumes something more basic: that something is alive.
Goodpaster: To avoid arbitrary distinctions, we should
ground morality in a life criterion: anything
alive is morally considerable.
Respect for Nature:
A Theory of Environmental Ethics (1986)
Paul W. Taylor
Another Biocentric Environmental Ethic
Gary Varner
Varner develops a psycho-biological theory of individual
welfare.
And Another Biocentric Environmental Ethic
Nicholas Agar
Agar develops a theory based on living things having biopreferences.
And Still Another
Biocentric Environmental Ethic
James Sterba uses liberal justice to ground a biocentric environmental ethic:
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An organism has a good of its own if it can be harmed or benefited.
If an organism has a good of its own, it is wrong to harm it unless we
have a good reason for doing so.
There are no non-question-begging reasons to assume that human
interests always override the good of a nonhuman organism.
An organism that has a good of its own has moral standing and is thus
subject to the same fundamental principles of justice that govern human
relationships.
Liberal justice—a balancing of liberty and equality—is the most
defensible principle of social justice to guide human-nonhuman
relationships.
Sterba argues that species and ecosystems can also be said to have goods of
their own. Sterba’s EE thus bridges biocentrism and ecocentrism.
Aldo Leopold’s Land Ethic
Ecocentrism
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Ecocentrists believe that anthropocentrism, zoocentrism, and
biocentrism are all inadequate because of their individualist focus.
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From ecology: We cannot fully understand an organism without
also examining things such as:
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its species
its interaction within species populations
its relationship with ecosystem processes
what it eats
what eats it
etc.
Ecocentrism: We cannot fully understand the value of an organism
without also locating value in holistic entities, and probably also in
processes and relationships.
Ecocentrism
The central feature of ecocentrism is its holism.
Three kinds of holism:
1.
Epistemological or methodological holism: We cannot understand
something or have knowledge of it without taking into account
holistic entities, processes, and relationships.
2.
Metaphysical holism: Holistic entities really exist.
3.
Ethical holism: holistic entities (and probably processes and
relationships as well) have noninstrumental value.
Three Problems for Ecocentrism
1.
Getting its ecology right
2.
Naturalistic fallacy: Trying to derive values straight
from facts, or prescriptive norms about what we should
do straight from descriptive, factual statements
3.
Ecofascism
“Animal Liberation: A Triangular Affair”
(1980) by J. Baird Callicott
Ethical Humanism (Anthropocentrism)
Humane Moralism
(Animal Liberation)
Leopold’s Land Ethic
(Holistic Ecocentrism)
Callicott’s Conclusions
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Animal liberationists fail to make a distinction between domestic and
wild animals, but this distinction is crucial.
From the perspective of Aldo Leopold’s land ethic, many domestic
animal species ruin nature.
Domestic animals have no natural behavior.
We cannot “liberate” animals back to the wild; if left alone, many
domesticated species might go extinct.
It is wrong to prevent pain (sentientism) because pain provides
important information for nervous systems.
Animal liberation denies our natural participation in nature through
activities such as hunting.
“Animal Liberation versus the Land Ethic”
(1981) by Edward Johnson
Johnson replies to Callicott:
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Animal liberation is directed toward individual animals that can be
liberated; there is no direct concern with species.
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The sentientist point about pain is that pointless pain is morally
wrong.
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Natural participation with nature? What’s this?
Tom Regan pours fuel on the fire between
animal ethics and environmental ethics
(1983)
“The implications of [Leopold’s] view include the clear prospect that the
individual may be sacrificed for the greater biotic good, in the name of ‘the
integrity, stability, and beauty of the biotic community.’ It is difficult to see
how the notion of the rights of the individual could find a home within a
view that…might be fairly dubbed ‘environmental fascism.’ To use
Leopold’s telling phrase, man is ‘only a member of the biotic team,’ and as
such has the same moral standing as any other ‘member’ of ‘the team.’ If,
to take an extreme, fanciful but, it is hoped, not unfair example, the
situation we faced was either to kill a rare wildflower or a (plentiful) human
being, and if the wildflower, as a ‘team member,’ would contribute more to
‘the integrity, stability, and beauty of the biotic community’ than the
human, then presumably we would not be doing wrong if we killed the
human and saved the wildflower.” (pp. 361-362 from The Case for Animal
Rights, 1983, bold and underline added)
“Animal Liberation and Environmental
Ethics: Bad Marriage, Quick Divorce” (1984)
Mark Sagoff:
1.
If animal liberationists such as Singer are committed to
minimizing the suffering of animals, logically they should be
committed to intervening in wild nature to lessen suffering. This
could lead to many proposals and policies such as killing
predators.
2.
But these kinds of proposals and policies will strike an
environmentalist as being absurd.
Thus, a holistic environmental ethic cannot stem from the interests of
individual animals.
A Possible Utilitarian Response
1.
Utilitarian intervention to minimize suffering in the lives of wild
animals might damage ecosystems, resulting in a lower quality of
life for animals in the wild (and possibly a lower quality of life for
people).
2.
Removal of animals from the wild to minimize suffering might
likely lead to unhappier lives for the now captive animals.
Thus, leaving wild animals alone might be our best policy to minimize
animal suffering. This could result in a habitat ethic that might be
compatible with holistic environmental ethics.
A Possible Animal Rights Response
1.
A wild animal’s right to life is a right not to be killed by moral
agents (who have a duty to respect rights), but this doesn’t imply
a duty on the part of moral agents to protect the animal from
being killed by non-moral agents such as other wild animals.
2.
We should manage human wrongs and not wild animals.
Thus, respecting the rights of wild animals simply means letting them
be, with as little human interference as possible.
“Animal Liberation is an
Environmental Ethic” (1998) by Dale Jamieson
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Sentient humans and animals have primary value, while nonsentient entities have derivative value. But in some cases derivative
value should trump primary value.
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Animal liberation and environmental ethics can be likened to a
Hollywood romance:
1. They can complement each other—there are good animal
ethics and good environmental ethics reasons to not eat meat.
2. We can value non-sentient nature intrinsically and intensely.
3. An animal ethic can give us a habitat ethic that is
indistinguishable from a biocentric or ecocentric
environmental ethic