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Fragmentation, or the loss or breaking apart of previously intact natural covers (forest, meadow, shrubland), into smaller and disconnected pieces, threatens habitat for wildlife, particularly species that rely on large tracts of forest or meadow.
Fragmentation is the breaking apart of a previously contiguous natural cover (forest, grassland, meadow, shrubland), into smaller, disconnected pieces. Fragmentation results from clearing land for development or agriculture, strip-mining, or putting in place roads, utility rights-of-way (ROWs), or hedgerows where they cut through natural communities.
For natural areas it is important to limit fragmentation and the resultant increase in edge effects in order to maintain interior species habitat. Interior habitat in forest, grassland, or meadow is necessary to support healthy populations of many wildlife species of conservation concern. Interior species depend on interior habitat—the part more than 100 meters (305 feet) from the edge of any contrasting cover type—to meet their specific needs of microclimate, food, shelter, secure nesting sites, and protection from predators. Many forest-dwelling plants also benefit from forest-interior habitat. Edge areas expose them to increased wind, light, and heat, decreased humidity, and increased competition from invasive plants.
Forest fragmentation facilitates invasive species establishment. Edges allow light and wind to penetrate a forest stand, both of which help invasive species colonize and proliferate. The shape of a cover-type fragment affects the severity of fragmentation impacts. The higher the edge-to-area ratio, the greater the fraction of the total area an invasive species can overrun in a single growing season, speeding their spread. The shape with the lowest edge-to-area ratio is a circle; narrow shapes and branching shapes have the highest edge-to-area ratio and can even result in a forest stand or grassland/meadow area having no interior at all.
When fragmentation occurs, the amount of interior habitat drastically decreases and interior species have fewer resources to support their populations. The situation is worst when the same habitats on neighboring properties also decrease in size. Many species are limited in their ability to move across significantly different types of habitats. Resources in each fragment become scarcer as those species deplete them and can no longer access additional food or breeding areas.
Fragmentation can be avoided by protecting existing areas of natural cover and preventing development, conversion to lawn, or incursion of roads and ROWs as much as possible. Previously cleared areas can also be restored to natural cover to increase the size of habitat areas and decrease fragmentation. Grasslands and meadows fragmented by hedgerows can be made habitable for grassland/meadow-interior species by removing the hedgerows. In landscapes that are a patchwork of both forest and grassland or meadow, judicious selection of areas to be converted from one to the other can increase the interior area of the cover type assigned higher priority, or of both.