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Habitat Fragmentation

What is habitat fragmentation?
How does fragmentation occur?
How does fragmentation affect wildlife?
What do "edge effects" do to the habitat itself?

Habitat Fragmentation is the disruption of a habitat by breaking it into smaller and more isolated fragments. Roads, dams, water pollution, fences, and land sprawl can all break up various natural areas such as grasslands, wetlands, forests, etc. This process, can result the separation of a species so that they may not be able to disperse itself or continue reproducing, and this disrupted species may eventually die off locally or even globally.

Fragmentation occurs in a series of stages. In a forest, for example, in an effort to create field space, patches of cleared land appear within a once continuous forest. Next, as regional and agricultural development occur, more forested land is cleared of its trees to facilitate the expansion of agriculture. The enlarged, widening patches now start to coalesce into large open areas of land, so that patches of forested land now exist within a large agricultural landscape. Although the state is mostly forested, Pennsylvania's forests are highly fragmented with less than half remaining forests in core or interior forest type cover. Wildlife that depend upon contiguous forest have declined within the state.

Fragmented land becomes more exposed to more wind and more sunlight. Patch edges become more accessible to predators and parasites that may be present in adjacent fields or developed areas. The reduction of the total habitat area may directly reduce the total population size. As a population attempts to disperseitself to other patches, individuals have to cross relatively inhospitable terrain and expose itself temporarily to harsh environmental conditions, starvation, and predators. If a prey species wanders too close to the edge of their protective habitat, they can be quickly captured and eaten. Other species may be excellent competitors deep within their own specialized habitat, but are less successful against species found at the edge of their habitat that are more habituated to the wide variety of conditions found between two different habitats.

Edge effects occur when these separations change the surroundings wilderness. Temperatures and wind patterns may change as a result of fragmentation. Many habitats have such an impact on the physical environment that they can create their own microclimate. For example, dense forests tend to be shadier, more humid, and less windy than adjacent unforested land, and this pattern becomes more pronounced deeper into the forest.

For more information on habitat fragmentation, visit the following site: http://www.dcnr.state.pa.us/wlhabitat/execsummary.htm
http://www.nrdc.org/cities/smartGrowth/pwild.asp