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Transcript
Populations and ecosystem
management
Species concepts
• Policy/debate centers on species.
• Consider six categories currently used.
Species Categories
• Keystone species: effect greater than
biomass. Beavers
• Indicator species: Indicative of conditions
good or bad: stoneflies, diptera larve
• Umbrella species: If secure, provide
habitat for many: Grizzly bear.
Species Categories
• Flagship species: Elicits emotional
feelings: Whales, tigers, koala
• Vulnerable species: susceptible to
extinction: Black-footed ferrets.
• Economically important species: positive
or negative consequences: elk zebra
mussels.
Species categories
• A species can be in more than one.
• Used in debates over species
conservation.
• Use to prioritize.
Species management
• Single species management
Metapopulations
• Most survival models , e.g. PVA and MVP,
good for overall assessment.
• Fail to incorporate spatial population
complexity that can affect survival
• Metapopulation model tries to incorporate
spatial complexity.
What is it?
• Not all populations homogeneous.
• Subdivided into semi discreet clusters or
subpopulations.
• Size and distance among them varies
• Probability of extinction related to
subpopulation size.
• Probability of re-colonization related to
distance.
Structure
• Small populations tend to go extinct more
often (deaths > births): SINKS
• Larger ones tend to persist AND provide
emigrates (births > deaths): SOURCES
• Rescue effect
Structure
Metapopulation Model
• Size important for source vs sink
• Distance and juxtaposition important for
rescue.
• Conceptual but does not include much
about matrix in which they exist.
• Dispersal (essential for maintenance)
mediated by habitat quality so distance is
not only factor.
Landscape-level Issues.
• Logical extension upward from
species/population considerations.
• Dealing with real organisms living in real
space in real time.
• Must live within landscapes.
• Landscapes determine health
of species populations.
Landscape issues
• So what are some of the landscape
issues?
• Basically issues that affect species
persistence
1) Habitat loss
2) Habitat Fragmentation*
3) Matrix quality
Habitat fragmentation
- Conversion of contiguous area of native
vegetation into pattern of remnant
patches within matrix of altered habitat.
Example
Example??
• Is this fragmentation??
• Natural vs
• Man-made??
• Key is altered!
Process
• Different forms
• Perforation:
3
- isolated altered
patches.
• Internal:
- Roads
- Gradual process.
2
1
Process
How does it happen? Example
Edge effects
• One of the major results of fragmentation.
• Principle quite simple: Use in chemistry!
• Smaller the fragments, greater the edge
area.
• Why important?
Impacts of edge
• Many species evolved within large
unfragmented habitat (edge sensitive).
• Conditions along edges.
• Abiotic.
- Sharp change in: temperature, relative
humidity, sunlight, etc.
• Affect conditions for energy capture of
species not adapted to these changes.
Impact of edges
• Biotic factors.
- increased predation by edge generalists
- Crows, brown-headed cow birds, blue
jays, etc.
• Buffer effects.
-edge effect not just a pencil line around
patch.
Buffers
• Hostile conditions will extend into patch.
• Distance depends on variety of factors:
- vegetation, aspect, etc., species.
- Functional fragment size determined by
fragment shape.
Examples
Example
Increased Isolation
• As Fragment habitat, fragments can
become more separated.
Increased Isolation
•
•
•
•
How does it affect?
Create metapopulation structure
If dispersal-sensitive, can be problems.
How dispersal-sensitive?
- Morphology: seed dispersal, tortoises.
- Physiological: Heat stress
- Behavioral: Not used to open areas,
Landscape Mosaic
• Spatial characteristics of all natural and
human-created aspects of environment.
• Shape
• Size
• Type
• Juxtaposition.
• Etc.
Landscape Mosaic
• How all elements are embedded in real
space.
• Two points important:
• 1) Mosaic not static, can change:
• 2) components not isolated:
interconnected.
Landscape Matrix
• Most extensive, most connected or
most influential landscape element in
an area.
• Can be man-made or natural
• Influences ecological processes
• Helps manager determine conservation
issues.
A tale of two matrices
Real Life Examples
Managing biodiversity across
landscapes
• Most effective way to protect diversity is
in-situ.
• Reasons:
- Cost of ex-situ
- Lose of natural selection
- remains part of natural landscape
How to protect biodiversity?
• Historically via protected areas.
- can be well planned to represent
ecosystems.
- most cases represent “popular” ones.
Tall Grass Prairie National Park?
• Can we protect enough?
- 5% of land mass in US is fully protected
- 5 % under some type of protection.
How do we protect the
“unprotected’?
• What ecosystem management is about.
• Integrate conservation with sustainable
development (ecotourism, grazing, forestry
practices, etc.)
• Blend need of biodiversity and humans.
Considerations: Protected
areas.
• Starting point:
• Given we want to protect a species or an
ecosystem within a protected area, what
do we focus on?
• Area, Shape, and Isolation important.
Area
• Area: matter of scale again.
- Larger the better: know that!
- Larger the area, harder to agree on
protecting!
- Usually size of area we can protect:
Doubt if we can set aside another
Yellowstone Park!
Example Mapimi
• Core or Nuclear
area.
• Differing levels of
Use.
Shape
• Shape is important
• How use in protected area scheme?
1) avoid long narrow areas (buffer and
edge effect).
Amount of edge important:
2) Strive to reduce edge
Example
• Changing use patterns of an area.
Isolation
• So few protected areas, often separated
by large distances.
• Review reasons why isolation important
• How reduce this isolation?
• Main tool is Corridors
Corridors
What is a Corridor?
Are there different types of corridors?
Does it have to be linear?
Will all wildlife use a corridor?
What are corridors?
• Strips of ecosystem that facilitate
movement of species between larger
landscape patches.
• What kinds of movements?
1) Natal dispersal
2) Density-dependent dispersal.
3) Seasonal migrations
Today 4:00
Illick 5
• The ecology of Fear: A unifying paradigm
in ecology??
• Dr. John W. Laundré
Types of corridors
• Book initially had “linear” strips of ….
• Idea that corridors are usually linear in
shape.
• Many are: riparian habitat.
• Some habitat remnants: fence lines
• Some are “waste land” Unusable for
human purposes.
• Some are actually planned!!
Types of Corridors
• Corridors can also be viewed as
spatially discrete habitat patches
- ie stepping stones along a migratory
pathway
Example: planned, why?
•
•
•
•
Many for roads.
Roads fragment
Roads isolate
Roads kill
Roads
• Impact all but amphibians
and reptiles affected the
most.
Do they work?
Fig. 3. Wolf paths through the study area
one winter prior to (left) and two winters
following (right) corridor restoration
here
Do they work?
• The answer is Yes!
• Most times!
• What makes a good \
corridor?
Developing corridors
• How to begin?
• Select species of concern.
- Limits focus to manageable level.
• Identify sites you want to connect.
- Sources/sinks
• Map corridor and evaluate features.
- Identify ownerships, human elements.
• Design and implement monitoring system.
- Opportunity to learn
Rules of thumb?
• Some considerations of features.
1) Gaps
-- Limited by species ability to cross
-- Day use vs night use
2) Width
3) Length
Corridor Width
• Width depends on.
1) Surrounding land.
More similar/narrower
2)Scaled with corridor length: longer/wider
- average width of home range
3) Habitat quality in corridor
Home range width
• Varies with body mass
• Larger species
= wider corridors.
Considerations:
• How mobile
• Human domination
• Corridor length
Corridor length
• Depends on mobility:
1) More mobile animals can move through
longer corridors
2) How will function: just day travel, multiple
days, generational movements.
Potential Disadvantages of Corridors
- Most corridors are linear edge habitat,
some species will not utilize and subject
to increased mortality risk.
- Don’t fully understand what species do
and do not utilize corridors
- Use as a band-aid approach to a larger
problem.
Potential Disadvantages of
Corridors
• Dispersal of invasive species
• Ironically, success of movement of
invasive species indicates that corridors
CAN be successful!
• Filtering becomes important.
Summary
•
•
•
•
Corridors have their place
Well planned ones seem to work
Indeed may be band-aides but necessary
others