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Habitat Fragmentation and Loss

Habitat Fragmentation and Loss. Habitat fragmentation = the breaking apart of continuous habitat 1. reduction in the total amount of original habitat (i.e. habitat loss) 2. subdivision of the remaining habitat into fragments, remnants, or patches (i.e. habitat fragmentation)

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Habitat Fragmentation and Loss

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  1. Habitat Fragmentation and Loss

  2. Habitat fragmentation = the breaking apart of continuous habitat • 1. reduction in the total amount of original habitat (i.e. habitat loss) • 2. subdivision of the remaining habitat into fragments, remnants, or patches (i.e. habitat fragmentation) • 3. introduction of new forms of area-use to replace lost habitat

  3. Stages of Landscape Change • 1. Intact landscapes • 2. Variegated landscapes • 3. Fragmented • 4. Relict landscapes McIntyre and Hobbs (1999)

  4. Species-Area Relationships • Relationship between the size of a habitat (or “island”) and the number of species present • Generally, for every 10x increase in habitat area you can expect a doubling in species abundance

  5. Theory of Island Biogeography • Preston (1962) and MacArthur & Wilson (1963, 1967) • Proposed that the number of species on an island is in a dynamic equilibrium between immigration and extinction

  6. Island Biogeography: Area Effect

  7. Island Biogeography: Distance Effect

  8. Island Biogeography and Conservation • Areas of application: • How large should preserves be? • How does isolation affect species number in reserves? • What kinds of species will survive if area is reduced?

  9. Fragmentation and its Effects on Community Structure • Loss of species richness • Changes in species interactions • Changes to trophic levels • Loss of foundation species

  10. Edge Effects • High perimeter length to area ratio • Greatest effects occur in small remnant areas and those with complex shapes

  11. Deterministic and Stochastic Processes • Deterministic = factors that are not necessarily a direct consequence of habitat fragmentation but arise from land uses typically associated with it. • Stochastic (chance) = natural factors related to demographics, genetic variation, environmental fluctuations, catastrophic events

  12. Effects of Isolation • Impairs regular movements of organisms • Impairs seasonal/migratory movements • Impairs dispersal movements

  13. Metapopulations • Local populations interconnected by movements of individuals between them

  14. Salt Marsh Habitat Fragmentation, Degradation and Loss

  15. Problems Facing Salt Marshes • Agriculture • Channelization • Flood control/Levees • Roadways • Development

  16. http://gallery.usgs.gov/search/ Case Study: Louisiana

  17. Case Study: Louisiana

  18. Seagrass Habitat Fragmentation, Degradation and Loss

  19. Prop Scars!

  20. Coral Reef Habitat Fragmentation, Degradation and Loss

  21. Mangrove Habitat Fragmentation, Degradation and Loss

  22. Conservation in Fragmented Seascapes • Protect and expand the amount of habitat • Enhance the quality of the habitat • Manage across the entire seascape • Increase connectivity • Plan for the long-term • Learn from current and previous efforts

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