The Conservation Value of Peripheral Populations: the Supporting Science

Traditionally, populations at the periphery of the geographic range of a species have been regarded as having little value in conserving biodiversity. This view developed from the expectation that populations at the edge of their geographic range are more vulnerable to extinction than populations in the central portion of the range. Conservation biologists have also assumed that the genetic diversity of a species is greatest near the center of its geographic range. This low regard for peripheral populations has been incorporated into guidelines for conserving biodiversity. Conservation practitioners are told to direct limited conservation resources to conserving central populations because peripheral populations have little chance of survival and are genetically impoverished. These expectations and their related guidelines have caused officials at many governmental levels to question including species at the periphery of their distribution in lists of protected species. Despite the often uncritical acceptance of the low conservation value of peripheral populations, recent research suggests that peripheral populations may play an important role in conserving declining species. Contrary to expectations, in species that have undergone large range contractions, peripheral populations persist significantly more often than do the central populations. In addition, examinations of the genetic diversity of populations across the geographic range of a species are beginning to call in to question the assumption of higher central diversity. Furthermore, studies on both persistence and genetics suggest that the distinction between central and peripheral populations may not be an important distinction for conserving biodiversity. Thus, conservation plans should include populations found both near the center and the periphery of a species' distribution.