Habitat Fragmentation

1. Habitat Fragmentation • Anthropogenic disturbances and habitat fragmentation are the greatest threat to biodiversity. • The end result is a patchwork of small, isolated natural areas in a sea of disturbance. • Disturbed habitat favors Aweedy species@.

2. Landscapes are Naturally Mosaics • As a result of patchiness, habitat quality for species varies spatially. • Persistence of metapopulations depends on the efficiency of dispersal of individuals and/or propagules from one patch to another. • The number of species on an island represents a balance between immigration and extinction.

3. The Fragmentation Process • gaps are formed within a vegetative matrix • as gaps grow, the connectivity of the original vegetation becomes broken. • a tenfold decrease in habitat area typically cuts the species richness in half

4. Biological Consequences of Fragmentation • species may survive in a matrix of human land use e.g. White-tailed Deer • species may survive by maintaining a viable population within individual fragments e.g. Plethodonouachitae, Rich Mountain Salamander • being highly mobile may allow a species to incorporate several patches into a home range e.g. Pileated Woodpecker. • initial exclusion • barriers to migration/isolation • crowding • edge effects- edge may be an ecological sink. • changes in species composition • increase in exotic invasions

5. Source and Sink Populations

8. Conclusions/Recommendations • all landscapes should be managed as shifting, interconnected mosaics. • it may be better to surround habitat fragments with highly dissimilar habitats; a low- contrast matrix may draw species into sink habitats. • avoid further fragmentation • identify natural wildlife migration routes. • maintain native vegetation along streams.