Plants and animals rely on connected patches of habitat to move around their territories, find mates, hunt, forage, and reproduce. In connected riparian areas, animals can move easily between different areas, each providing something the organism needs. Humans can impact habitat connectivity by building roads and clearing vegetation for houses and crops. This breaks the landscape up, or fragments it, separating quality habitat areas from each other with areas that are paved or otherwise developed. You can see what happens when an area is fragmented by looking at the difference between the two animations below.

When a riparian area becomes fragmented, it can prevent some wildlife species from finding other members of their kind. As their habitats become smaller because of development or land clearing, the distance between members of a species increases. The developed areas can become barriers if species are unwilling to cross them or if they are killed when they try to cross.

Population effects of isolation will occasionally lead wildlife populations living in small patches to die off in that immediate area. Causes include: the inability to access required habitats, disease, disturbance, increase in predators or competitors, and fluctuations in birth and death rates.

By creating small and isolated patches of natural space, fragmentation can divide a once large wildlife population into smaller, more vulnerable populations. Small wildlife populations are more likely to succumb to random events that can harm them than large populations. If a population of red-backed voles, say, dies off in a small riparian patch because of a fire or disease outbreak and there is not another population in a nearby patch, the species cannot re-establish a new population.

Wildlife populations can be susceptible to a number of genetic effects from isolation as well. Close relatives are more likely to mate as populations become isolated. Common results of breeding between relatives are increased juvenile mortality, decreased fertility, and reduced overall ability of a species to survive.

Small populations are likely to become more genetically similar — the potential for change and adaptation is lost. A species may lose a rare genetic trait that could help it survive under different circumstances.

In most species, some individuals will disperse away from their natal population to ensure genetic diversity. In fragmented landscapes, dispersal is not possible, and so there is no opportunity for outside individuals to bring new genes to a population with declining genetic diversity.