White Clay Creek State Park is frequently visited by hikers, cross-country runners and nature enthusiasts. The park is also home to over 100 species of animals, whose habitat depends on access to native plants. These naturally-occurring plants evolved with the surrounding ecosystem, providing food for insects, which in turn provide food for various creatures.
However, invasive plant species, which are not native to the region, cripple the White Clay Creek ecosystem. Non-native plants are considered invasive because they are aggressive, easily propagate and the wildlife that normally controls the plant’s population in its native environment is not there.
“Our parks and natural areas are often choked with invasive plants,” Susan Barton, a plant and soil sciences professor at the university, said. “The problem with invasives is they outcompete the native plants and create a monoculture.”
Biodiversity, or a variety of life in an ecosystem, is a major factor in the health of an ecosystem. A wide range of animals, plants and microorganisms are necessary for plant pollination, soil health and carbon absorption. Even if some native species are negatively impacted by human activity, biodiversity can still be maintained. However, once invasive species develop a monoculture, an area with no plant diversity, entire ecosystems collapse.
“Because the invasives are outcompeting the natives, our native insects which are specialists cannot rear their young or reproduce,” Barton said.
The loss of native plants has both secondary and tertiary effects. For example, once the invasives overtake the natives, insects are forced to migrate to find a new habitat, resulting in birds not having the needed insects to feed their young.
Lawson Schultz is president of the Native Species Initiative, a registered student organization at the university. Schultz, along with 15 other members of the organization, volunteer their time to remove invasive species from the Judge Morris Estate section of White Clay Creek State Park.
Their volunteer work “revolves around removing invasive plants and planting natives, but before we can plant natives, we have to completely clear the area of invasive species,” Shultz said.
Through their volunteer efforts, members of the Native Species Initiative have removed over a dozen different invasive species, according to Schultz.
In the early afternoon of a chilly Sunday in October, volunteers arrived at Judge Morris Estate and formed a circle to discuss the day’s objective. Terri Tipping, a master naturalist, explained that the volunteers will split into two groups: one designated to plant native species and the other to continue removing invasives. The meeting concluded and volunteers from their respective groups wielded native plants or pruning loppers.
John Enderle, the team lead for the removal group, instructed volunteers to remove viburnum, an invasive shrub with green leaves and red berries. Before entering the forest, Tipping said to the volunteers that “roughly 30% of plants in the forest are invasive” – just because they are green, does not mean that they are native.
For two hours the pruning team cut the viburnum close to the ground, followed by Enderle applying a herbicide to prevent the viburnum from regrowing. Several waist-high piles of viburnum began to accumulate.
About 50 yards away, in an area already clear of invasives, the planting team was hard at work only stopping briefly to rest a hand on their shovel and catch their breath. The volunteers were digging holes, loosening roots and placing the natives in their new homes. When it was time to pack up for the day, 100 native plants were added to the Judge Morris Estate section of White Clay Creek State Park.
Restoring native ecosystems is a financially difficult process, according to Schultz.
“The park is only able to plant natives if they receive grants”, Schultz said. “The removal of invasives is no-cost through volunteering, but the natives have to actually be purchased.”
State legislators have tried to proactively halt the purchase and sale of invasive species with Senate Bill No. 22. The recent bill took effect in July of this year and “prohibits the import, export, sale, transport, distribution, or propagation of any plant identified by the Secretary of the Department of Agriculture, with the advice of the Delaware Native Species Commission, as an invasive plant.”
Barton said that the bill covers invasives like “Japanese stilt grass, which nobody buys to purposefully propagate.” But, more importantly, invasives like “Norway maple, winged burning bush, Japanese barberry and the three big ground covers, Japanese pachysandra, vinca minor and English ivy are now on the banned list.”
The plants listed are more likely to be found in residential suburban neighborhoods, according to Barton. Although these non-natives are well maintained by homeowners, does not mean the local ecosystem remains unscathed.
In a 2009 study titled “Impact of Native Plants on Bird and Butterfly Biodiversity in Suburban Landscapes,” researchers found that suburban landscapes that had native trees and shrubs supported significantly more caterpillars and greater bird abundance and diversity, compared to non-native landscapes. Additionally, regional bird species were eight times more abundant in native landscapes, according to the study.
Schultz has been a part of the Native Species Initiative for three years and has noticed substantial improvements to White Clay Creek State Park.“Every week we go to the park to volunteer, and I can definitely see a difference,” Schultz said. “Overall, the volunteering is a nice opportunity to just actually contribute and to see your contributions to the park.”
Members of the public can volunteer to assist the forest restoration effort at White Clay Creek State Park by signing up at DNREC’s State Park Volunteer Calendar online. Check out the calendar and sign up! It’s very satisfying to remove invasive plants and see what you can accomplish in two hours. A lot!