Biodiversity

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• Biodiversity Definitions and Assessment
• Definitions
• Components of Biodiversity
• The term biodiversity often is used incorrectly
  or incompletely
• Not synonymous with species diversity
• Encompasses three measures
• Species Diversity
• Species richness Total number of species
• Often cited incorrectly as biodiversity
• Fairly simple to estimate from rarefaction curves
• Evenness Proportions of species in a community
• More difficult to determine (requires more
  complete survey)
• Genetic Diversity Variety of genotypes
• Ecosystem Diversity Variety of habitat types

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• Biodiversity Definitions and Assessment
• Definitions
• Components of Biodiversity
• The term biodiversity often is used incorrectly
  or incompletely
• Not synonymous with species diversity
• Encompasses three measures
• Species Diversity
• Species richness Total number of species
• Often cited incorrectly as biodiversity
• Fairly simple to estimate from rarefaction curves
• Evenness Proportions of species in a community
• More difficult to determine (requires more
  complete survey)
• Genetic Diversity Variety of genotypes
• Keystone Species

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• Biodiversity Definitions and Assessment
• Estimates of Biodiversity
• Described species 1.8 million
• Insects gt 1,000,000 species
• Plants gt 290,000 species
• Probably an underestimate
• Only 5000 species of bacteria
• Less conspicuous species studied less often
• Estimates range from 5 30 million
• Around 300 new species described each day
• Average estimate 17.5 million
• Splitting of taxa more common than lumping
• Tendency to increase number of described species
• Cryptic species

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• Biodiversity Definitions and Assessment
• Estimates of Extinction Rates
• Geological history
• Periods of extinction followed by periods of
  rapid speciation (every 26 million years)
• How do we estimate rates of extinction??
• Problems
• Difficult to know when a species is extinct
• Ex Coelacanth, ivory billed woodpecker, giant
  lemur
• Species distributed unevenly (patchy
  distribution)
• Species affected unevenly by habitat loss
• Extinctions may not happen immediately
• Short-lived species show effects rapidly
• Long-lived species may appear to be unaffected
  for long periods of time
• Biologically extinct Populations not
  self-sustaining
• Living dead - Janzen
• Uncertainty about number of species in an area
• Wilson No precise estimate can be made of the
  numbers of species being extinguished in the rain
  forests or in other major habitats, for the
  simple reason that we do not know the numbers of
  species originally present

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• Biodiversity Definitions and Assessment
• Estimates of Extinction Rates
• Estimation Methods
• Area-species relationship (MacArthur Wilson)
• Estimate biodiversity for a small area
• Extrapolate estimate to area of habitat
• Species Area0.25 (0.15-0.35)
• Increase area 10X ? Increase species 2X
• Estimate rate at which ecosystem area is being
  reduced
• Calculate extinction rate based on predicted
  reduction in species richness from reduction in
  habitat area
• Current estimate 17,500 species year-1
• 1 out of every 1000 species on Earth each year
• Background rate from fossil record
• 1 out of every 1-10 million species on Earth each
  year

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• Biodiversity Definitions and Assessment
• Estimates of Extinction Rates
• Estimation Methods
• Area-species relationship (MacArthur Wilson)
• Estimate biodiversity for a small area
• Extrapolate estimate to area of habitat
• Species Area0.25 (0.15-0.35)
• Increase area 10X ? Increase species 2X
• Estimate rate at which ecosystem area is being
  reduced
• Calculate extinction rate based on predicted
  reduction in species richness from reduction in
  habitat area
• Current estimates 17,500 species year-1
• 1 out of every 1000 species on Earth each year
• Myers 40,000 year-1
• Lomborg 1033 documented from 1600 1998
• The Skeptical Environmentalist
• Background rate from fossil record
• 1 out of every 1-10 million species year-1

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• Biodiversity Definitions and Assessment
• Estimates of Extinction Rates
• Point Estimates may be unreliable and thus
  invalid
• No action should be taken until biodiversity loss
  is demonstrated and shown to be harmful
• Counterpoint Wilson Projections using
  area-species relationships in tropical settings
  (where most of biodiversity loss currently is
  happening) are conservative
• Tropical species have localized distributions
  that make them especially vulnerable to habitat
  loss
• Damaging loss of genetic diversity may occur,
  even if outright extinction of a species doesnt
  happen

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• Biodiversity Definitions and Assessment
• Biodiversity Hotspots
• Myers Up to 20 of the worlds 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
• Biodiversity
• Endemism
• Risk of habitat degradation/loss
• Concept originally intended for tropical and
  subtropical areas
• Endemism less prevalent in temperate and polar
  regions

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• Biodiversity Factors
• Nutrient Availability
• Oligotrophic
• Dominated by a few species able to survive on
  limited nutrients
• Low diversity, Low biomass
• Mesotrophic
• Support greater numbers of species
• Rapid colonizers held in check by nutrient
  limitation
• Less aggressive species capable of surviving
• High diversity, Medium biomass
• Eutrophic
• Dominated by a few species able to grow and/or
  colonize rapidly with abundant nutrients
• Low diversity, High biomass

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• Biodiversity Factors
• Selective Colonization/Mortality
• Colonization
• Excellent colonizers (r-selected) may dominate
  newly available habitats
• Mortality
• Predation
• Ex Birds with colorful plumage
• Ex Sea urchins (sushi)
• Species-specific diseases/pests
• Ex Dutch elm disease
• Ex Western bark beetles

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• Biodiversity Factors
• Habitat Disturbance
• Non-selective habitat disturbance has potential
  to increase diversity
• Prevents competitive exclusion
• Intermediate disturbance ? Maximum diversity

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• Biodiversity Factors
• Habitat Disturbance
• Fire and fire-dependent species
• Ex Peters Mountain Mallow (Iliamna corei)
• Discovered in 1927 (50 plants)
• Endemic to meadow in western Virginia
• 1986 - Three plants remaining
• Not setting seed
• Listed as endangered
• Research on seeds indicated importance of fire
• Cracks hard seed coat, aiding germination
• Removes competing vegetation
• Had been suppressed in the area
• Controlled burns in 1992 and 1993 led to
  appearance of 500 seedlings

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• Biodiversity Factors
• Habitat Fragmentation/Destruction
• 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, esp. when territory size fragment
  size
• Fragments may not support self-sustaining
  populations (rely on immigration from outside)

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• Mount Hood National Forest, Oregon
• Patches due to timber removal

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• Biodiversity Factors
• Habitat Fragmentation/Destruction
• 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, esp. when territory size fragment
  size
• Fragments may not support self-sustaining
  populations (rely on immigration from outside)

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• Biodiversity Factors
• Habitat Fragmentation/Destruction
• Fragmentation increases edge effects
• Positive effects
• Increased light to plant species at edges
• Negative effects
• Increased predation by animals foraging at
  habitat edge
• Ex Nesting success among migratory birds in
  Midwestern forests lower in fragments due to
  increased nest predation and parasitism by
  cowbirds

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• Biodiversity Factors
• Exotic Species
• Species invasions may profoundly affect
  ecosystems
• Detrimental exotic species usually are
• Superior competitors
• Ex Argentine ants, starlings, zebra mussels
• Effective predators
• Ex Nile perch, mongeese

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• Biodiversity Factors
• Exotic Species
• Zebra mussel
• Competitor in Great Lakes and elsewhere
• Transported from Europe in ballast water
• Fouling organism
• Restricts movement of water through intake pipes
• Colonizes boat hulls, pier pilings, buoys, etc.
• Fouls other organisms (clams, mussels)
• Filter feeder removes larvae and particulate
  material
• Outcompetes native shellfish species for food and
  space
• Removes larvae from water

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• Biodiversity Factors
• Exotic Species
• Mongoose
• Predator in Hawaii
• Introduced in 1883 to combat rat population
• Prey on native birds
• Lionfish
• Venomous predator
• Introduced in Caribbean/W Atlantic ca. early/mid
  1990s
• Preys on 65 spp. of fishes
• No natural predators

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Nile perch Lake Victoria
Brown tree snake - Guam
Argentine ants - California
Caulerpa taxifolia - California
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• Biodiversity Value
• Value to Humans
• Economic
• Ex Lomborg 3-33 trillion annually
• Biodiversity loss could lead to removal of
  species that benefit humans but arent currently
  known to do so
• Ex Chapin et al. suggest increased frequency of
  Lyme disease in 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
• Counter Many pharmaceutical companies now use
  directed design to search for new drugs

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• Biodiversity Value
• Value to Humans
• Problem Benefits may not be obvious
• Difficult to convince people that its important
  to preserve something with no immediately
  apparent intrinsic value to them (charisma?)
• Ex Economic value of viral resistance added to
  commercial strains of perennial corn through
  hybridization with teosinte (Mexican wild grass)
  is 230-300 million
• Ex Weedy tomatoes from Peru
• Discovered in 1962 during search for potatoes
• Seeds sent to researcher at UC Davis who used
  plants to breed with other tomatoes
• In 1980 after nearly 10 generations of crossing
  and backcrossing, new strains were produced with
  larger fruit, improved pigmentation and increased
  concentrations of sugars and soluble solids

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• Biodiversity Value
• Ecosystem Value
• Biodiversity can have large effects on ecosystem
  stability and productivity
• Benefits of biodiversity
• Productivity
• Halving species richness reduces productivity by
  10-20 (Tilman)
• Average plot with one plant species is less than
  half as productive as a plot with 24-32 species
• Question Can these results be extrapolated to
  other systems and time/space scales?
• Nutrient retention
• Loss of nutrients through leaching is reduced
  when diversity is high
• Caveat Studies to date have focused on low
  diversity communities (Why?) can those results
  be generalized?

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• Biodiversity Value
• Ecosystem Value
• Benefits of biodiversity
• Ecosystem stability
• Mechanism
• Multiple species within a trophic level compete
  for resources
• If abundance of one species declines due to
  perturbation, competing species may increase in
  abundance
• Individual species abundances may vary, but
  community as a whole is more stable with more
  species
• Consequences
• High diversity doesnt guarantee that individual
  populations wont fluctuate
• Ex Higher diversity (unfertilized) plots of
  native plant species maintained more biomass
  during drought than lower diversity (fertilized)
  plots
• High diversity may confer greater resistance to
  pests and diseases
• Ex Higher diversity plots of native plant
  species had greater resistance to fungal
  diseases, reduced predation by herbivorous
  insects and reduced invasion by weeds

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• Biodiversity Value
• Ecosystem Value
• Considerations
• Species richness vs. Species evenness
• Simple species richness may be deceptive as an
  indicator of biodiversity and ecosystem stability
• Evenness usually responds more rapidly to
  perturbation than richness and may have important
  ecosystem consequences
• 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)
• Ex Sea otters/Sea urchins/Kelp forests in
  eastern Pacific Ocean
• Question How many species are required to
  maintain normal ecosystem function and
  stability?
• No magic number
• 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

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• Biodiversity Management
• Strategies outlined in Convention on Biological
  Diversity
• Developed between 1988 and 1992
• Opened for ratification at UN Conference on
  Environment and Development (Rio Earth Summit)
• Ratified by 168 nations went into force in Dec
  1992
• Objectives the conservation of biological
  diversity, the sustainable use of its components
  and the fair and equitable sharing of the
  benefits arising out of the utilization of
  genetic resources
• Articles 8-9 specify a combination of in situ and
  ex situ conservation measures
• Primary use of in situ conservation
• Use of ex situ measures as a complement