Ecosystems, ecosystem management, ecosystem health

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• 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

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• 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

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• 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

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• Exam Thursday, May 11th, 8am