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Habitat Fragmentation

Explore the process of breaking contiguous habitats into smaller pieces, leading to altered community and ecosystem processes. Understand the impacts on species' abundance and distribution, reproductive success, and formation of "islands." Delve into how different species are affected by fragmentation and edge effects, with a focus on area-sensitive and ground-nesting species. Discover how rare, wide-ranging, and interior-dependent species may be more vulnerable to habitat fragmentation.

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Habitat Fragmentation

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  1. Habitat Fragmentation • Process of breaking contiguous unit into smaller pieces; area & distance components

  2. Habitat Fragmentation

  3. Habitat Fragmentation • Process of breaking contiguous unit into smaller pieces; area & distance components (includes habitat loss?) • Leads to:

  4. Habitat Fragmentation • Community & Ecosystem processes altered

  5. Habitat Fragmentation • First-Order Effects: fragmentation leads to change in a species’ abundance and/or distribution

  6. Habitat Fragmentation • Higher-Order Effects: fragmentation indirectly leads to change in a species abundance and/or distribution via altered species interactions • Altered community-level interactions – relates to 1st order effects

  7. HABITAT FRAGMENTATION Predators - Abundance - Distribution - Foraging Behaviors + Ground-Nesting Birds - Abundance - Distribution – – – Avian Competitors Avian Prey Brood Parasites + + Parasites - Abundance - Distribution REPRODUCTIVE SUCCESS

  8. Formation of Terrestrial “Islands”

  9. Patch size #patches Patch isolation Edge

  10. Implications with Diseases

  11. Theory predicts that small populations > P(extinction) by random fluctuations in demography and loss of genetic diversity through genetic drift

  12. Isolation effects

  13. Carnivores & Reserves Area of Reserve (km^2) (A) black bear (F) lion (I) African wild dog (J) grizzly bear

  14. Habitat Fragmentation • area-sensitive species: species that require minimum patch size for daily life requirements • Edge effects:

  15. 250 m 250 m 31% 64% Total Area = 1 km2 250 m 14% Total Area = 5 km2 Total Area = 0.5 km2 Edge Effects

  16. 250 m 250 m 31% 64% Total Area = 1 km2 250 m 14% Total Area = 5 km2 Total Area = 0.5 km2 Edge Effects

  17. Edge Effects

  18. Edge Effects • Habitat surrounding a patch can: • change abiotic conditions; e.g., temp. • change biotic interactions, e.g., predation • Example of nest predation = edge effect of approximately 50 m into forest patch

  19. Carnivores & Reserves Area of Reserve (km^2) (A) black bear (F) lion (I) African wild dog (J) grizzly bear

  20. Habitat Fragmentation: Species-Specific Sensitivity? • Rare species = more vulnerable • Wide ranging species = large-area requirements • Species with reduced mobility = more vulnerable • Species with low fecundity (related to rarity?) • Species with short life cycle (or multi-stage life cycle?)

  21. Habitat Fragmentation: Species-Specific Sensitivity? • Ground-nesting birds may be more vulnerable (30-60% reduction in last 25 yrs) • Interior-dependent species • Species vulnerable to human exploitation or disturbance • Specialist species?

  22. Habitat Fragmentation: Species-Specific Sensitivity? • Generalizations are a good start • (= hypotheses?), but a little more complex than that……

  23. Swihart et al. 2003. Diversity and Distributions 9:1-8.

  24. Differential Sensitivities to Habitat Alteration • Niche breadth (diet & habitat) – inverse relation • Range periphery = more sensitive (W & N) • Body size = mobility (allometric relation) • Social and territorial behavior (limited K) Swihart et al. 2003

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