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Habitat Fragmentation

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

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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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