Transcript Objectives

Objectives
• Conservation approaches:
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populations/species
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entire habitats
• Habitat destruction/fragmentation causes much
extinction
• Conservation biology relates to landscape
and community ecology
• Plans for preserves
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Size, number, shape, pattern
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Stepping stones, corridors
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Preserve community structure
Conservation Biology IB 451 Spring 2011
Landscape Ecology NRES 465 Spring 11
Conservation Planning: Approach 2
• Preserve habitats/areas,
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especially ‘biodiversity hotspots’
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high species number
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high endemism
Endemic species:
restricted to small geographic area;
especially prominent on islands
Deterministic causes of extinctions:
the ‘evil quintet’
1 habitat destruction and fragmentation
(67% of cases)
2 overkill (overexploit)
3 chains of extinction
• introduced species
• emerging diseases
Habitat changes caused by human land use
limit conservation strategies.
Habitat reduction and fragmentation
lead to endangered species
Habitat reduction and elimination
• Some habitats are eliminated altogether.
• Fragmentation causes other problems:
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reduced total area
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reduced interior/edge ratio
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reduced habitat heterogeneity
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reduced connectivity
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greater inter-fragment distance
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unable to migrate with changing climate
Smaller fragments support fewer animals.
Figure 1
*** What is the pattern? What explains it?
Figure 2
Which size
of area is
needed?
Will a park be
Sufficient?
Principles for design of nature preserves:
If create preserve from large expanse of
uniform habitat:
• larger is better than smaller
• SLOSS: single large or several small?
• one large area is better than several small
that sum to same size
• add corridors or ‘stepping stones’
• circular is better than elongate with more
edge
Why are larger areas better?
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support more species by reducing
likelihood of stochastic extinction
promote genetic diversity
buffer populations against
disturbance
avoid ‘edge effects’
offer freedom to migrate
***Summarize two major results.
Corridors enhance migration between patches
and maintain population cohesion.
Figure 3
***What are advantages of corridors?
• Are there disadvantages?
If creating preserve out of diverse
habitat:
• Several small in different habitats better
than one large in uniform habitat
• Plan for migration --->
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use corridors
stepping stones to link habitats
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bridge roads and pipelines that impede
movement
Consider community structure
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Top-down control of trophic abundances
Cascade effects: indirect effects extended
through multiple levels
Can have chain of extinctions if highly
dependent
Keystone organisms must be preserved
Non-redundant species, key species
that maintain stability/diversity
How does species (and functional) diversity
affect community response to disturbance?
Population models assume: large size
(> minimum viable population size);
no variation in average birth and death rates.
• In reality, randomness affects populations,
especially small ones:
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Catastrophe
Variation in environment
Stochastic (random sampling) processes
• Chance events may cause
small populations to go extinct.
• Minimum viable population size = >500
Probability of extinction increases over time;
increases with smaller initial population size.
Small populations are more likely to go extinct
due to random fluctuation in population size.
Figure 4
***Summarize the two main results. Provide a
reason for each result.
What traits enable a population to rescue a
small population from extinction? Figure 5
Rescue effect:
• Immigration from a large subpopulation
can keep a declining subpopulation from
inbreeding and going extinct.
• Can produce positive densitydependence: survival of subpopulations
increases with more subpopulations.
Mainland-island model:
Source provides emigrants to sink.
source
sinks
Figure 6
Sample exam ?
You are asked to design a national park system for a
tropical country.
1) How will the concept of ‘hot spots’ of diversity
influence your choice of areas to conserve?
• You have defined your locations. What are 4
principles that you will consider in the next
phase: their spatial design?
1) What specific attributes of parks are needed to
accommodate specific flora or fauna?
2) What general criteria related to preserve size
must be met to ensure long-term survival of
species? (assume habitat requirements are met)
Restoration Ecology
• Basic principles of ecology have practical
use for solutions to human problems
• Use research
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to better understand ecological processes
within highly disturbed ecosystems
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to enhance their complexity and long-term
persistence
NRES 420 Restoration Ecology
Objectives
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How blend science into practice
Important ecological principles for restoration
Population
Community
Landscape
Ecosystem
Practice of restoration
Illinois in Need of Restoration
• Clearly a need –
– Remaining habitat:
• 0.01% prairie
• 9.9% wetland
• 31.4% forest
– U.S. Rank:
• Indiana 48
• Illinois 49
• Iowa 50
Which level(s) of ecology are applicable?
POPULATION
ECOLOGY
COMMUNITY
ECOLOGY
RESTORATION ECOLOGY
ECOSYSTEM
ECOLOGY
LANDSCAPE
ECOLOGY
Goals:
Improve the ecology of a disturbed
area by:
– increasing diversity in highly disturbed system
– reestablishing characteristic species and community
structure/function
– reintroducing ecosystem function
(productivity and nutrient cycling)
– may have to start restoration from scratch
van Diggelen, Grootjans & Harris (2001)
Must apply ecological principles within a social
context…
POLICY
POPULATION
ECOLOGY
SOCIETY
COMMUNITY
ECOLOGY
ECOLOGICAL RESTORATION
ECOSYSTEM
ECOLOGY
LANDSCAPE
ECOLOGY
POLITICS
ECONOMICS
What aspects of Population Ecology
are relevant to Restoration Ecology?
• Species survival depends on
• maintaining minimum viable population levels
(>500).
• maintaining genetic diversity.
• using locally adapted genotypes.
• having a metapopulation structure with strong
source subpopulations to rescue sink ones.
What aspects of Community Ecology
are relevant to Restoration Ecology?
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Species-area relationships
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Island biogeography theory
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Problems with fragmented habitats
Intermediate disturbance hypothesis
Succession & community assembly
Diversity-stability theory; community
structure
How is the Species-Area curve relevant?
S = c + z log A
S = c Az
log S = log c + z log A
Figure 1
How is Island Biogeography Theory
relevant?
Immigration
Extinction
Small
Large
Near
Number of Species
Far
Figure 2
Patch relationships:
What are 2 take-home messages?
Figure 3
(From Forman, 1995)
Ecological Disturbance: What are its
dimensions? How relate to restoration?
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Figure 4
(D.T. Krohne, ‘General Ecology’)
Intermediate Disturbance Hypothesis:
at which level does disturbance aid
restoration? Why?
Competitive
exclusion
Disturbance Rate
Small
species
pool
Figure 5
Selected Natural & Anthropogenic
Disturbances: reversible vs. permanent
change?
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Natural Events**
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Fire
Disease epidemic
Flood
Herbivory
Drought
Hurricane, tornado, windstorm
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Avalanche, landslide
Volcanic eruption
Ice storm
** Entries
Anthropogenic Events**
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Residential development
Road, trail, railroad line
Telephone line, electrical
power line
Dam, water diversion, canal
Commercial development
Modern agriculture
Mining
Logging
Grazing
in italics connote reversible disturbances; others
represent long-term or permanent conversion of habitat.
Succession
• an orderly change in relative abundances of
dominant species in a community following a
disturbance until a stable community (‘climax’like predisturbance) results
Succession: Species-Species Interactions
How do these interactions influence community
development?
– Facilitation – early species make environment less suitable for
themselves, but more suitable
for later species -- nurse crops
- Tolerance - early species make environment less suitable for
recruitment of similar early species, but they neither help nor
hinder later species
- Inhibition - early species make environment inhospitable to laterarriving species
Early prairie reconstructions overly dominated by warm season
grasses
Community Assembly
• development of the ecological community
• determined by:
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random variation in species' colonization
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subsequent species interactions
Which orientation to follow?
Succession vs. Community Assembly
• Succession
– Deterministic
– Internal interactions & environment determine outcome
• Assembly
– Stochastic
– Supply of propagules determines outcome
– Multiple stable assemblies
How can succession be managed
to aid restoration?
General causes
Contributing processes
Modifying factors
Site availability
Disturbance
Size, severity, time, dispersion
Species availability
Dispersal
Landscape configuration, dispersal agents
Propagules
Land use, time since last disturbance
Resources
Soil, topography, site history
Ecophysiology
Germination requirements, assimilation rates,
growth rates, genetic differentiation
Life history
Allocation, reproductive timing & mode
Stress
Climate, site history, prior occupants
Competition
Competition, herbivory, resource availability
Allelopathy
Soil chemistry, microbes, neighboring species
Herbivory
Climate, predators, plant defenses & vigor,
community patchiness
Species performance
Restoration: Managing Succession
Designed Disturbance
Managing
Succession
Controlled
Colonization
Controlled Species
Performance
Managing Succession: in Practice
Designed Disturbance
Controlled Colonization
Controlled Species Performance
Burning
Burning
Burning
Bulldozing, Scraping, Topsoil Mixing
Broadcast seeding, Drill seeding,
Direct planting
Cabling
Cabling
Cutting
Grazing, Excluding grazers
Chopping, Clipping
Grazing
Fertilization, Reducing soil fertility
Flooding & draining
Fertilization, Herbicide spraying
Herbicide application
Herbicide application
Irrigation, Water level change
Mowing, Selective cutting
Plowing
Topsoiling & live soiling
Irrigation, Water level change
Solarization (thermal shock)
Rotovating
Soil compaction
Scraping
Soil fabrics
How can community structure influence
stability of restored community?
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Top-down control of trophic abundances
Cascade effects: indirect effects extended
through multiple levels
Can have chain of extinctions if highly
dependent
Keystone organisms must be preserved
Non-redundant species, key species
that maintain stability/diversity
How can Diversity Complexity Stability
be enhanced?
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An increase in the structural diversity of
vegetation increases species diversity.
Full restoration of native plant communities
sustains diverse wildlife populations.
A high diversity of plant species assures a
year-round food supply for the greatest
diversity of wildlife
Landscape Ecology
• How does the landscape context of the restoration
influence everything discussed earlier?
Spatial
Principles
• Large areas sustain more species than small areas.
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Many small patches in an area will help sustain regional
diversity.
Patch shape is as important as size.
Fragmentation of habitats, communities, and ecosystems
reduces diversity.
Isolated patches sustain fewer species than closely
associated patches.
Species diversity in patches connected by corridors >
than for disconnected patches.
A heterogeneous mosaic of community types sustains
more species & is more likely to support rare species
than a single homogeneous community.
Ecotones between natural communities support a variety
of species from both communities & species specific to
the ecotone.
Minimum Dynamic Area in Restoration
Design
 Largest patch
size
 Patch
longevity
 Disturbance
frequency
 Habitat
requirements
How is Ecosystem Ecology relevant?
• Interactions between the biotic & abiotic components
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affecting: flow of energy and cycling of matter