In 2012, District staff and then-board chair Jane Hartline (an enthusiastic volunteer) identified nine different landowners with potential to improve wildlife habitat at their 10 Sauvie Island ponds, which total 6.5 acres. The project began with a turtle study, paid for with District funds, to see which sites were already being used by turtles and which held the most promise for turtle habitat. Staff and volunteers assessed baseline conditions and took surveys in late winter-early spring of amphibian egg masses in order to determine which frog and salamander species were using the ponds. Additional site visits were conducted with various specialists, including local wildlife biologists, an OSU Extension aquatic invasive species and watershed health specialist, a seasoned botanist, and a Xerces Society aquatic invertebrate (insects, snails, etc.) expert. We considered water quality as well as plant and wildlife habitat features and species at each pond.
Project participants conferred on what changes might be made at each pond, where they found various dragonflies, fish, snails, water beetles, and desirable plants such as native wapato and spatterdock. The style of pond management varied among landowners. The next stage of the project was to make recommendations that matched landowner objectives and budgets and to prioritize sites and actions. Conservation actions can include felling trees into the ponds to add basking areas for turtles and dragonflies; adding native aquatic vegetation, which is both food for turtles and other small wildlife, and structure for egg laying, hiding and perching; controlling invasive species such as purple loosestrife and reed canary grass; adding or managing vegetation to get the right balance or shade and sun and improve wildlife access; and changing strategies for algae and mosquito control.
Starting in late 2013, the District partnered with one Sauvie Island landowner who had a 1/3 acre pond to kill the aggressive reed canary grass and plant approximately 800 native wetland trees and shrubs over the course of two years. Because of the exceptionally wet conditions in spring of 2014, some of the plants in the 15 foot band around the pond drowned and we needed to re-plant in later winter / spring of 2015. In the fall of 2015, the District increased biodiversity by sowing native grasses and wetland seed, as well as wapato and sneezeweed seed collected locally on the island. The District took advantage of areas with sparse vegetation or bare soil — including under the native beggar’s tick plants and on ground unearthed by moles — around the pond. Grass seeds were made up of native riparian species such as tufted hairgrass, and our wetland mix included American sloughgrass, western mannagrass, spreading rush and slough sedge.
Staff is also improving habitat in ponds and other wetlands beyond Sauvie Island. One site in the Rock Creek watershed, where staff assisted on a larger conservation and livestock manure management project, has 4 ponds heavily used by red-legged frogs, a designated “sensitive species.” The ponds were improved by adding diversity to the riparian and aquatic vegetation in the form of native wetland seed and plant plugs. Various sedges and rushes were included in the mix.