Creating Successful Vernal Pools: A Literature Review and Advice for Practitioners

Abstract

Vernal pools provide critical breeding habitat for amphibians adapted to temporary waters, but they seldom receive the same level of protection as permanent wetlands. In response to continued degradation and loss of pools, managers often attempt to mitigate losses through pool creation or restoration. However, mitigation efforts often fail to provide suitable aquatic habitat for vernal pool amphibians. We review the literature on pool creation in northeastern and central North America, highlighting how and why constructed pools often fail to support amphibian related objectives. We recommend that practitioners consider the complex ecology of pool ecosystems and the historical and current distribution of pools and other wetlands in their local context before designing pool mitigation projects. Using vernal pool creation as a mitigation option should be a last resort (i.e., when elimination of natural pools is unavoidable). Monitoring should be target specific and conducted for at least 5 years. Topographic, geologic, and other local factors affecting pool hydrology and ecology vary regionally; pool creation remains an imperfect science that will only advance by documenting failures and successes. We recommend an adaptive management approach to vernal pool creation in which the effectiveness of techniques is evaluated and refined based on research.

Using spatial demographic network models to optimize habitat management decisions

“…The reasons for ringed salamanders failing to breed in nearly half of the wetlands in the Focal Area are varied, and are unknown in many cases. The presence of fish and short or ephemeral hydroperiods are 2 of the primary reasons that ringed salamanders fail to breed or successfully recruit from a pond (Peterman et al , Anderson et al , Semlitsch et al ), both of which can be modified through direct management (Walston and Mullin , Calhoun et al ). It is important, however, to carefully assess all relevant structural habitat features to ensure that restoration efforts provide more than partial remediation.…”

Using performance standards to guide vernal pool restoration and adaptive management

“…A more recent study on the classification of vernal pools in California determined that performance standards were lacking standardization as to what plant community attributes are measured, had variable lengths of monitoring time following project implementation, and metrics intended to evaluate ecological parameters were not ecologically relevant (Barbour et al ). A 2014 review of vernal pool creation projects in the northeastern United States provides a similar critique of performance standards, noting that they are insufficient indicators of restored habitat function, particularly with regard to the maintenance of faunal communities (Calhoun et al ).…”

“…Barbour et al () provide a series of useful suggestions for clarifying and improving the De Weese () vegetation performance standards including measurable definitions of vigor (biomass accumulation) and reproductive activity (seed production), criterion to address exotic species, and several new criteria that are community oriented rather than species oriented. Similarly, Calhoun et al () do not recommend the use of species richness as a performance standard because richness may reflect a high number of exotic species, and does not necessarily relate to vernal pool health. Rather, community composition is a suggested standard that can provide a more ecologically relevant measure of success (Calhoun et al ).…”

“…Similarly, Calhoun et al () do not recommend the use of species richness as a performance standard because richness may reflect a high number of exotic species, and does not necessarily relate to vernal pool health. Rather, community composition is a suggested standard that can provide a more ecologically relevant measure of success (Calhoun et al ). Lastly, Barbour et al () suggest deleting the De Weese () criterion of VPE species dominance, as they contend it does not promote heterogeneity of constructed pools.…”

“…In addition, it is assumed but worthy to note that performance standard guidelines should be based on a comparison of restored pools to appropriate, naturally occurring reference pools that are regionally relevant (both within and outside of the site if possible) (Barbour et al ; Bauder et al ). To create appropriate performance standards, data collection from reference pools should take place over time rather than in one season to account for system dynamics (which are highly variable for vernal pools) and similarly, restored pool monitoring should take place over a different seasons (De Weese ; Bauder et al ; Calhoun et al ).…”