Global Ecology and Conservation (Jun 2023)
PVA-based assessment of resiliency, redundancy, and representation in an imperiled freshwater turtle
Abstract
Conservation decisions benefit from projections about the future condition of a species as generated using population viability analysis (PVA) or other analytical techniques. For listing decisions made under the US Endangered Species Act, future projections contribute to the Species Status Assessment process and are evaluated using the concepts of resiliency, redundancy, and representation (the three Rs). Although the use of PVA is widespread, explicit linkage of PVA outcomes to the three Rs is rare. To demonstrate this linkage, the status of the Blanding’s turtle (Emydoidea blandingii), an endangered species in Illinois, was evaluated using the three Rs. PVA was used to evaluate resiliency using the conservation target that, in the absence of catastrophes, projected population extinction risk be ≤ 5% over 100 years. By this criterion, populations of ≥ 50 adults, occupying ≥ 100 ha of protected habitat, and possessing demographic characteristics consistent with stable or increasing numbers have high resiliency. PVA was used to evaluate redundancy based on the conservation target that, in the presence of catastrophes, metapopulations were projected to retain ≥ 95% of initial genetic diversity over 100 years. By this criterion, regions with intermediate and high resiliency subpopulations totaling ≥ 200 adults have high redundancy. Information from genetic analyses, natural division and watershed boundaries, and the historic distribution of Blanding’s were used to identify five representation units in Illinois. Currently, there are few high resiliency populations, only one high redundancy unit, and statewide Blanding’s turtle representation is low. PVA projections using current estimated population sizes indicate that without effective management, resiliency and redundancy will continue to decline and representation will remain low. The methods used here hold promise for evaluating the three Rs in species of conservation concern more generally.
