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Ecosystems, ecosystem management, ecosystem health

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Title: Ecosystems, ecosystem management, ecosystem health


1
  • Ecosystems, ecosystem management, ecosystem
    health
  • Alternative stable states
  • Resilience-resistance

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  • Alternative stable states when an ecosystem can
    exist in two (or more) different forms under the
    same environmental and climate conditions
  • Small disturbances can cause large changes
  • Changes in ecosystems can happen quickly

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Vegetation, nutrients, and water clarity in
shallow lakes
More vegetation Less vegetation
Turbid
Clear
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Vegetation reduces turbidity
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Grazing in black grama grasslands
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  • Today
  • Ecosystems under stress
  • Ecosystem vs. traditional management

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  • Stress an external force that causes changes to
    an ecosystem (disturbance)
  • can be natural or human-caused
  • Four types of human-caused stressors
  • physical restructuring (land use, clearing)
  • introduction of exotic species
  • pollution
  • harvesting organisms

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  • Symptoms of stress
  • Changes in nutrient cycling
  • movement of nutrients from living things into
    soils
  • transport of nutrients out of ecosystems

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  • pollution can reduce decomposition, causing
    litter to accumulate
  • nutrients from soils run off into streams,
    rivers, lakes

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  • Changes in primary productivity
  • aquatic systems usually show increased
    productivity with stress
  • algal blooms
  • red tides
  • eutrophication

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  • terrestrial systems stress reduces primary
    productivity

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  • Changes in species diversity
  • stress usually reduces diversity
  • can increase diversity if habitat heterogeneity
    is increased

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Freshwater mussels
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  • Retrogression
  • the opposite of succession shifting to an
    earlier successional stage

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  • Changes in size distribution of species
  • largest species tend to be smaller in stressed
    ecosystems

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Ecosystem Management
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  • Traditional View of Management
  • Narrow view
  • small scale
  • manage one species at a time
  • Based on equilibrium world view (no alternative
    stable states)
  • Goal was to facilitate extraction of natural
    resources
  • Rely on tight controls

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  • Ecosystem Management a new approach to
    maintaining entire ecosystems for long-term
    sustainability

37
  • Scale of Management
  • Traditional approach manage single species in
    small areas
  • Ecosystem approach manage on multiple levels,
    potentially over large areas

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  • Different Scales in Ecosystem Management
  • Populations of critical organisms
  • Indicator species represent a larger group of
    species or a habitat type
  • Keystone species have a disproportionately
    large effect on their community or ecosystem

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  • Umbrella species require large blocks of
    habitat species requiring less habitat fall
    under their umbrella
  • Vulnerable species threatened with extinction
  • Economically important species have monetary
    value

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  • Ecological processes
  • goal is to maintain processes like flooding,
    fire, herbivory, and predation

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  • Landscape structure
  • manage for landscape structure that will maintain
    community

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  • Today
  • Finish ecosystem management
  • Final exam
  • Tearful farewell

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  • Traditional View of Management
  • Narrow view
  • small scale
  • manage one species at a time
  • Based on equilibrium world view (no alternative
    stable states)
  • Goal was to facilitate extraction of natural
    resources
  • Rely on tight controls

49
  • Stability in ecosystems
  • Traditional approach assumed ecosystems were
    stable and reached equilibrium
  • Ecosystem approach embraces variation

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  • Where stability matters
  • Predator-prey cycles
  • Climax vs. earlier successional stages
  • Effects of diversity in food webs

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  • Resistance the degree to which an ecosystem is
    avoids changing following a disturbance
  • Resilience the capacity to recover after a
    disturbance
  • if disturbance exceeds the ecosystems
    resilience, it can switch to an alternate state

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cold spell
high resistance
N
low resistance
time
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cold spell
high resilience
N
low resilience
time
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  • When the range of natural variation in a system
    is reduced, the system loses resilience

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  • Variation and resilience Examples
  • Increased genetic variation makes populations
    more resilient to environmental change
  • stocking one fish genotype -gt no resilience

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  • Natural resource management should strive to
    maintain types and ranges of natural variation in
    ecosystems.

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  • Resource extraction
  • Traditional approach based on maximizing
    harvest
  • Ecosystem approach values biodiversity for
    itself

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  • Control over Ecosystems
  • Traditional approach command and control over
    ecosystems
  • Ecosystem approach ultimately, we are not in
    charge

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  • How to manage in the face of uncertainty and lack
    of control?
  • Adaptive management treat management as an
    experiment
  • try different techniques
  • evaluate performance
  • use knowledge to improve management

65
  • Exam Thursday, May 11th, 8am
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