Conservation Biology

1
Conservation Biology

• Lecture 10
• Campbell (Fifth Edn.), pp 1154-1175
• www.ent.orst.edu/jepsonp

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The Biodiversity Crisis

• Extinction is a natural phenomenon
• The rate of extinction underlies the biodiversity
  crisis
• The actual rate is not known, but could be as
  high as 1000-10,000 the background level of 1
  species per million per year

3
Extinction rates

• Most accurate for well known taxa e.g. birds
• Species/area relationships are used to make
  estimates
• A rule of thumb 50 of species lost if 90 of
  habitat is lost
• Examples
• 11 of 9040 known bird species are endangered
• 680 of 20,000 known US plant species are in
  danger of extinction
• 20 of known fresh water fish are endangered or
  threatened
• There are many undiscovered species, particularly
  amongst the arthropods, nematodes, fungi and
  prokaryotes
• Even the list of known mammals has grown by 15
  in the last decade

4
Threats to biodiversity

• Habitat destruction
• agriculture, urban development, forestry, mining,
  pollution etc.
• Competition by exotic species
• rates of introduction have increased
• displacement by introduced species is at least
  partially responsible for 68 of listings for
  rare and endangered species
• Over-exploitation
• over-fishing
• harvesting of non-target species

5

• Invasion by the fire ant (Solenopsis invicta)
• Accidentally imported in 1918 at the port of
  Mobile
• Fire ants displace native ant species (15 down
  to 5 spp in one part of Texas

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The significance of biodiversity

• Biophilia
• Sources of crops, fibers and medicines
  ecosystem services
• 25 of US pharmaceuticals contain substances
  discovered from plants
• Loss of genetic potential

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Conservation strategies

• Preservation setting aside an area to be free of
  development
• Resource conservation e.g. multi-use and
  multi-purpose management of lands by BLM in USA
• Evolutionary/ecological view preservation of
  populations, communities and functions to
  maintain a healthy biosphere

8
The geographic distribution of biodiversity

• Correlations with geographic gradients
• e.g. clines in distribution correlated with
  latitude (with maxima in the tropics)
• Energy availability increased solar
  radiation/primary productivity in the tropics
• Habitat heterogeneity greater local disturbance
  in the tropics (treefalls, floods and
  hurricanes), greater patchiness
• Niche specialization Tropical climates may
  facilitate narrower niches and greater resource
  partitioning
• Population interactions Greater diversity
  reduces the likelihood of species becoming
  dominant
• The relative importance of these as explanatory
  mechanisms may vary with latitude

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Bird species density in Central and North America
100
50
200
150
250
500
650
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Biodiversity hot-spots

• A small area with exceptional concentrations of
  species
• Species often endemic (30 of bird species
  endemic, and found on 2 of the land area)
• 70 of bird species are found in 221 hot spots
• 76 of bird hot spots are in the tropics
• There are 18 vascular plant hot spots, 0,5 of
  the earths area, with 50,000 (20) vascular
  plant species
• six of these 18 have lost gt90 of their area
• also therefore, hot spots of extinction
• Island faunas are under particular threat, as are
  migratory species where more than one habitat
  requires conservation

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Tropical forest and dry shrub lands contain
biodiversity hot spots for vascular plants
Tropical Forest Hot Spots
Chaparral Hot spots
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Conservation at the population and species levels

• Much of conservation at the species level (e.g.
  endangered species act).
• How do we account for genetic diversity and
  differences between populations?
• Habitat fragmentation and the dynamics of
  sub-divided populations
• Metapopulations a network of sub-populations in
  habitats that vary in quality. Persistent
  sub-populations may act as a source for
  populations in low quality patches
• metapopulations are maintained by dispersal

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• Bull trout (Salvelinus confluentus)
  metapopulation structure
• Sub-populations with differing life histories
  are requirements are now isolated, preventing
  gene flow, reducing population size and
  threatening extinction

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5
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Egg laying sites in mountain streams
Regular dispersal and gene flow
Clear-cut (logged) areas
Irregular, infrequent dispersal and minimal gene
flow
Roads
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Source-sink dynamics

• Reproduction exceeds mortality for dispersive
  individuals in source habitats
• Mortality exceeds reproduction in sink habitats
• Source habitats may only harbor a small of
  individuals
• Wild-sub populations of peregrine falcon (Falco
  peregrinus) in S. California (sink habitat) now
  preserved by conservation efforts in N.
  California (source habitat) populations

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Population viability analysis (PVA)

• Incorporates information on genetic variability
  and life history (sex ratios, are at first
  reproduction, fecundity, birth rates and death
  rates)
• Also details of predation, parasitism,
  inter-specific competition and habitat
  disturbance
• Predicts likelihood of survival over a number of
  generations, using specific details of
  metapopulation sub-habitats

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Minimum Viable Population Size (MVP)

• MVP The smallest number of individuals needed to
  perpetuate a population, sub-population or
  species
• Minimum dynamic area the area required to
  sustain the MVP
• Estimates of MVP require knowledge of Effective
  Population Size (Ne)
• Ne 4NmNf/Nm Nf
• where f and m represent females and males that
  successfully breed
• Populations must retain sufficient genetic
  diversity to be evolutionarily adaptable

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Analyzing viability in nature

• Only a small number of species can be analyzed in
  detail
• Models are abstractions of reality
• Models for a limited number of species guide
  broader conservation strategies

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• Plant species threatened with extinction that
  have been subjected to MVP analysis
• urbanization, fragmentation and harvest for food
  threaten both
• MVPs are 170 for ginseng and 300 to 1030 for
  leek
• only 20 ginseng populations are known to have
  gt170 individuals

Wild ginseng
Wild leek
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Conservation at community, ecosystem and
landscape levels

• Landscapes are regional assemblages of
  interacting ecosystems landscape ecology is a
  new and evolving discipline
• Edges and corridors are important elements of the
  landscape
• edge effects limit species distributions
• edges can have unique communities they can
  promote or decrease local biodiversity
• corridors can promote dispersal and sustain
  metapopulations

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Nature reserves

• Zoned reserve systems may offer a manageable
  solution to the problem of providing extensive
  nature reserves
• Some areas can be intensively managed
• Restoration ecology rebuilds damaged habitats and
  may involve the bioremediation of toxins
• Sustainable development, and the Sustainable
  Biosphere Initiative, exploit ecological ideas in
  the development of economic, social and
  environmental policy

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Zoned reserves in Costa Rica
National parks
Buffer zones
Urban, industrial