The situation when a continuous habitat has become divided into separate, often isolated small patches interspersed with other habitats. Small fragments of habitats can only support small populations of fauna and these are more vulnerable to extinction. The patches may not even be habitable by species occupying the original undivided habitat. The fragmentation also frequently obstructs species from immigrating between populations.

Habitat fragmentation stems from geological processes that slowly alter the layout of the physical environment or human activities such as land clearing, housing, urban development and construction of roads or other infrastructure. Adverse effects sometimes are not immediately noticeable and sufficient habitats may ostensibly be maintained. However inbreeding, lack of territories and food shortage are some of the problems small populations can encounter. Fragmentation of habitats is therefore expected to lead to losses of species diversity in the longer term.