The presence of invasive species within the woodland areas of the Easter Lake Watershed has caused the contribution of abnormal amounts of sediment into Easter Lake. The 891 acres of woodland within the watershed are estimated to contribute 36 tons of sediment and 125 pounds of phosphorus each year into Easter Lake decreasing water quality.
Historically land within the Easter Lake watershed was predominantly prairie with woodland areas in what is now Easter Lake and Ewing Parks. These areas included native trees, oak savannas, and even an old apple orchard that was planted by early residents to the area.
Invasive species such as honeysuckle, multiflora rose, buckthorn, oriental bittersweet, and others have taken over the woodlands. Native vegetation including oak trees and grasses have been choked out resulting in poor wildlife habitat, increased soil erosion into Easter Lake, and have made woodland areas inaccessible for public use.
Erosion is a serious concern which happens in these areas when invasives like honeysuckle block out sunlight in the tree understory taking away the chance for native vegetation to grow. Bare soil then easily washes away into the Easter Lake and Yeader Creek decreasing water clarity and increasing the potential for algal blooms.
Using the universal soil loss equation (USLE), it has been estimated annual soil loss could be reduced from 2.4 tons/acre to 0.7 tons/acre if invasive species are removed and native vegetation reestablished. To realize these reductions, Polk County Conservation Board and the City of Des Moines have developed an aggressive plan to restore the woodlands back to a natural healthy ecosystem.
Since spring 2014, the City and County have utilized forestry mowers to clear areas allowing sunlight to reach the ground and give native oak trees the room they need to grow. Additionally, volunteers have regularly helped in Easter Lake Park and Ewing Park to clear invasive species. After initial invasive species removal, these areas will continue to be revisited with strategic pesticide applications and controlled burns to manage species resprout.
As of early fall 2018, the City of Des Moines and Polk County Conservation Board with the help of volunteers have removed invasive species from over 130 acres of woodland areas in Easter Lake and Ewing Parks.