Conservation Biology- Habitat Fragmentation and Edge Effects

What is habitat fragmentation?

It is the process whereby a large, continuous habitat is both reduced in are and divided into two or more fragments that are often isolated from each other. It is the emergence of discontinuities in an organism's preferred environment.

What does fragmentation do?

It eliminated habitats for those species requiring large unbroken blocks of habitat such as a bear and large cats.

What are the causes of fragmentation?

Urbanization
Agriculture
Deforestation
Resource Extraction
Fences
Roads
Flood Control and Hydroelectric Dams
Oil and Gas Pipelines

What activities create a mosaic of forested and unforested areas in many regions that were once completely covered with forests?

Clear-Cutting

What is an avenue for invasion by humans and exotic species?

Roads

What are barriers for dispersal?

Dams and Roads

What reduces the amount of habitat and habitat type available?

Habitat Loss

What does fragmentation result in?

It results in the pieces of habitat increasing in insularity with larger edges as well as a loss of total habitat.

What are its effects?

Initial Exclusion
Isolation
Island Bio geography
Edge Effects

What are the three important ways habitat fragments differ from the original habitat?

- Fragments have a greater amount of edge per area of habitat and a greater exposure to edge effects
-The center of each habitat fragment is closer to an edge
-A formerly continuous habitat hosting large populations is divided into pieces, with smaller populations

Remember that size matters!

Larger patches have more interior habitat and smaller patches have less or no interior habitat.

When are populations typically more stable and sustainable and less susceptible to local extinction?

In large patches

What is the effect of having more edge habitat and less interior space?

Edge species increase and interior species decrease.

What is one of the best documented effects of fragmentation?

Edge Effects

Edge Effects do what?

They bring changes in species composition with invasion of exotic species.

What happens near the edges?

Predation can be significantly higher as the densities and movements of animals are higher.

Habitat fragmentation greatly increases the amount of edge habitat and also changes the micro environment at the fragment edge including what?

Altering Light
Temperature
Wind
Humidity
Incidence of fire

These edge effects can effect species in the ecosystem by?

Microclimates changes
Increased Incidence of Fire
Interspecies Interaction
Potential for disease

What increases the incidence of fire?

Increase wind
Lower humidity
Higher temperatures

Road edges represent what for invasive species?

The dispersal route

What is a major source of mortality?

Animals attempting to cross roads and coming into contact with motor vehicles.

To deal with this mortality what are highway officials doing?

They are building animals underpasses and overpasses (AKA Wildlife Corridors)

What is a Corridor?

A natural or artificial connection between two pieces of fragmented habitat.

What do corridors facilitate?

Everyday home range movements, seasonal and breeding migrations, dispersal, and range shifts in response to environmental and climatic changes.

What is immigration?

Moving into an area

What is emigration?

Moving out or exiting an area

What happens when a habitat is fragmented?

Species are confined to a single habitat fragment and may be unable to migrate over their normal range in search of that scarce resource.

What do barriers to dispersal do?

They restrict the ability to widely scattered pieces to find mates, leading to the loss of reproductive potential for many animal species.

Habitat fragmentation may cause what?

population decline and extinction

What are smaller populations more vulnerable to?

Inbreeding depression
Genetic drift
other problems associated with small population size

Connecting the fragments may be the key to what?

maintaining populations