Download Habitat Reserves - Conservation Biology - Lecture Slides | ECOL 406R and more Study notes Conservation biology in PDF only on Docsity! Habitat Reserves • What are they? • Why do we need them? • How do we design them? Objectives • Know the definition of a habitat reserve. • Know what habitat fragmentation is. • Know what the species-area curve looks like and the reasons underlying it. • Now some of the general rules for designing reserves, and the reasons underlying them. • Know how the “focal species” approach to reserve design works. • Know how disturbance regimes and external influences can affect habitat reserves. Metapopulation = a group of populations maintained by the interchange of individuals Strategies for Habitat Conservation • Set aside land and protect it – effective, but only 3-6% of the earth is under some form of protection. • Attempt to soften the effects of human use and combine human use of lands with habitat conservation. Design Considerations for Habitat Reserves • How much land do we need to set aside? • How big should the patches be, if the reserve is to be divided? • How should the patches be distributed relative to one another? • How can the reserve be maintained over time? Species-Area Relationship Size of Area Sampled (log) Number of Species Number of species increases as area sampled increases – WHY? • Environmental diversity and complexity • Minimum area requirements • Small population problems • Colonization rates Bigger is better than smaller better than Connect patches when possible. better than Arguments for and against this rule Advantages of Corridors • Potentially increases movement among patches • Potentially creates habitat for wide-ranging species • Potentially maintains habitat within corridors Disadvantages of Corridors • Potentially spreads problems (diseases, exotic species, fire) • May not be effective for some species • Cost can be high How much habitat is needed? Population Viability Analyses (PVA) • PVA models estimate population size, or rate of change (lambda = ). • PVA models can be deterministic or stochastic • Most complex PVA models are spatially explicit PROCESSES AFFECTING POPULATIONS POPULATION STATE VARIABLES Population size Age structure Sex ratio Productivity Survival POPULATION PERSISTENCE Demographic stochasticity Genetics Population regulation (dispersal) Environmental stochasticity (habitat quantity and quality) Management plan for the Northern Spotted Owl is an example of the focal species approach • PVA indicated that 1,500 breeding pairs would have a high likelihood of persistence over the long term. • Old-growth forests on public lands sufficient to support 1500 pairs were identified. • The patches were large enough to support at least 20 pairs/patch. • Patches were no more than 11 miles apart (distance young, emigrating spotted owls were capable of moving)\ • Matrix was maintained in a condition that would facilitate movement.
