Habitat fragmentation is the breaking up of a large area of uninterrupted habitat into smaller, isolated habitats. It can result from natural events such as volcanic eruptions, changes in the courses of rivers, forest fires, and climate change. It can also result from human activity, including deforestation, damming of rivers, draining wetlands, road building, the introduction of alien species, agriculture, and urbanization.
Habitat fragmentation can contribute to the endangering or extinction of some or many species and thus a reduction in biodiversity. One reason is that some species need large areas of habitat in order to obtain sufficient food and find mates. Fragmentation can also make it easier for harmful invasive species to enter habitats. In addition, it can reduce genetic diversity of a species because of the difficulty of animals moving among the fragmented habitats due to such factors as lack of food, lack of protection from predators that their native habitats provide, danger from crossing roads, and physical barriers. This results in more inbreeding and thereby reducing the resistance of the species to diseases and predators.
Habitats worldwide have experienced extreme fragmentation during the past several centuries as a result of human activity, and thus few large, undisturbed habitats remain, particularly in the northern latitudes. This has been a result an emphasis on business and economic goals (such as obtaining timber and expanding agriculture) and political considerations together with, until recent decades, a lack of understanding of the importance of maintaining habitats intact. Habitat fragmentation and loss is a major factor in the mass extinction that the earth is currently experiencing.
One proposed solution is the creation of wildlife corridors between fragmented habitats that allow species to move among them. For example, in some places underpasses or bridges have been constructed below or above busy roads to allow animals to move unimpeded between habitats. These have often been useful for helping protect some species, such as larger animals with great mobility such as wolves and mountain lions. However, they are much less useful for animals with low mobility, such as the giant panda and sloths as well as most plants.
In order to fully stop and begin to reverse habitat fragmentation and loss, however, much more needs to be done. This includes providing tax and other economic incentives, establishing region-wide zoning, creating large-sized wilderness areas, and promoting education to create greater awareness on the part of the general public, businesses and governments.