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Assessing impacts of wetland restoration and hydrological management on amphibians

This project builds on a 2017 CREOi amphibian research project, and will focus on baseline monitoring for amphibian presence, diversity and abundance as well as habitat characteristics (hydrology, water quality, and vegetation) in a series of seasonal and permanent ponds and wetlands in the study area. This study area is 480 acres of seasonally wet agricultural land and associated wetlands that is slated to be enhanced to benefit waterfowl, fish and agricultural usage as part of a project led by Ducks Unlimited and funded by U.S. Department of Fish and Wildlife. The planned enhancement work is designed to maintain winter flooding over wetlands and agricultural fields, thereby providing salmon and waterfowl with highly productive winter habitat, and then to facilitate spring drainage allowing farmers to access agricultural fields. Additionally, riparian and pond-side areas will be planted with native vegetation to create wildlife movement corridors, improve habitat structure, and shade waterways.

While these activities are gauged to enhance fish and waterfowl habitat, the impacts of this altered hydrology on amphibians are still uncertain. Maintenance of late winter flooding may increase the availability of oviposition habitat for native amphibians, and more complete spring drawdown could reduce bullfrog presence in some seasonally flooded areas, also benefiting native amphibians. However, too-rapid drawdown could reduce survivorship of egg masses of native species in shallowly ponded areas. Increases in riparian vegetation cover, while generally desirable, could have complex impacts as well. Additional tree and shrub cover may provide overwintering habitat for tree frogs and northwestern salamanders, and may even make these habitats suitable for red-legged frog, a locally declining species which has not been observed in these relatively open ponds. However, excessive shade could make sites less optimal as oviposition habitat for some species. An amphibian monitoring program at this site will allow us to evaluate the impacts of this kind of hydrological intervention on amphibians and assess whether increasing native vegetation improves conditions for these species.  ($15,000)