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:

- isolated altered

patches.

• Internal:

- Roads

- Gradual process. 1

23

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 4:00Illick 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

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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

Do they work?

• The answer is Yes!

• Most times!

• What makes a good \

corridor?

here

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