Habitats & Fragmentation

Question 1

What kind of geophysical processes does habitat heterogeneity often arise from?

Answer 1

Volcanism
Geological formation
Erosion
Fire

Question 2

What kind of human impacts affect spatial structure on ecosystems?

Answer 2

Resource harvesting
Pollution
Land clearance: Agriculture, industry, Residential

Leads to habitat loss and habitat fragmentation.

Question 3

How have human population explosions affected habitat?

Answer 3

Caused Large-scale deforestation

Question 5

How does patch size affect population size?

Answer 5

The smaller a patch is, the fewer species it will support.

Question 6

What is the threshold effect? And what are the four main hypotheses?

Answer 6

Linear - Biodiversity increases in a linear trend.

Fragmentation threshold - Biodiversity increases on a non-linear trend in response to changes in the total amount of forest in the landscape.

Forest+abundance -
Biodiversity increases in response to changes in the total amount of forest landscape and to an increase in bat abundance

Null -
Biodiversity does not vary in function of the amount of forest.

Question 7

What are the key concepts of habitat loss and fragmentation?

Answer 7

1. Patch size - smaller habitats contain fewer species than big patches.
2. Patch isolation - Theory of island biogeography.
   - No. of species determined by rates of immigration and extinction.
3. Crowding effects
4. Change in edge and center ratios.
5. Local and regional extinctions.

Question 8

How does an increased ratio of patch edge to patch area in highly fragmented ecosystems?

Answer 8

• Reduced average density recorded over a collection of fragments
• Increased risk of predation/ parasitism

Question 9

How do cascading effects, affect habitat islands?

Answer 9

When an area is too small, this will cause large carnivores to move out allowing the herbivores to increase.

With an increased herbivore pressure, this lowers the standing ground vegetation.

Question 10

What sort of species are vulnerable to fragmentation?

Answer 10

-Endemic species
-Wide-ranging species
-species with low fecundity
-Species with short life cycles
-large patch of interior species
-species subject to human
-exploitation/ persecution.

Question 11

How do edge effects, affect habitats and species?

Answer 11

An ecological trap - more likely to go extinct
Greater structural contrast - greater edge effects.
Lack of core.

Question 12

What can fragmentation be?

Answer 12

• A part of habitat loss
• As a change in habitat configuration.

Question 13

Can fragmentation be good?

Answer 13

Fragmentation effects may become severe when total habitat has been reduced (20-30%)

Question 14

How is fragmentation good?

How can dividing the same amount of habitat into smaller pieces affect species?

Answer 14

Persistence of predator-prey systems
refuge for prey
competitive species coexistence
stabilize single species systems

This is an important role of species among patches.

Question 15

What is habitat loss the main driver of?

Answer 15

species extinctions
Habitat loss often results in in habitat fragmentation.
Effects of habitat loss outweigh habitat fragmentation.