Barrier Impacts–
Population Fragmentation & Isolation

To the extent that road crossings act as barriers to animal passage, they can fragment and isolate populations. Smaller and more isolated populations are vulnerable to genetic change and extinction due to chance events. Genetic changes may result from sampling error (“genetic drift”) that occurs in small populations, or via inbreeding depression in very small populations. Local extinctions can result from demographic chance events (e.g. change in sex ratio), natural disturbances, or human impacts. As road crossings contribute to population fragmentation and isolation they undermine the viability of animal populations.

Example of fragmentation and isolation