This post was contributed by Emily Zefferman, Research Associate in Urban Ecological Restoration at the University of Tennessee, and a 2014 PhD graduate from the University of California Davis Graduate Group in Ecology.
Urban forests and greenways are increasingly-valued oases in cities across the United States and globally. These areas offer recreational opportunities to city dwellers, improve water and air quality, and provide important habitat for native species. However, many such areas suffer from a prevalence of exotic species, due to their high levels of disturbance and close proximity to intentionally introduced species.
Knoxville, Tennessee’s “Urban Wilderness” is no exception. This collection of private and public parks and land easements comprises approximately 1000 acres of forested land along the southern edge of the Tennessee River. While featuring scenic vistas, unique geologic features, shaded trails, and historical landmarks like former mining sites and Civil War-era forts and battlefields, the Urban Wilderness harbors a growing threat to the area’s native habitats: a massive infestation of invasive plant species. Among the worst are privet (Ligustrum spp.), honeysuckle (Lonicera spp.), English ivy (Hedera helix), multiflora rose (Rosa multiflora), and winter creeper (Euonymus fortunei), which cover much of the understory. These invasives displace native plants, cause irritation and injury to hikers (e.g. multiflora rose), and could impact native birds, insects, and other animals that use native plants as food and habitat.
In many areas of the Urban Wilderness, the understory is dominated by non-native shrubs like honeysuckle (Lonicera spp.), privet (Ligustrum spp.), and multiflora rose (Rosa multiflora). In this photo, taken in early spring, almost everything green is invasive.
While these invasive plant infestations have been well known to local land managers, no one had documented their extent throughout the Urban Wilderness—a crucial initial step for beginning to tackle the problem. Nor had there been a comprehensive effort to document the native biodiversity in the Urban Wilderness, to better understand the areas that need greatest protection. To begin to understand these ecological assets and challenges, a group of regional stakeholders began an effort in spring 2015 to create an “Ecological Inventory” of Knoxville’s Urban Wilderness. This project is led by researchers at the University of Tennessee Knoxville, with the help of a diverse group of partner organizations: the City of Knoxville, Legacy Parks Foundation, Discover Life in America, and the Tennessee Exotic Pest Plant Council. Coordination between stakeholders with different types of experience and expertise will benefit the overall project by allowing resources and knowledge to be shared and put towards a common goal. Cooperation is essential for managing an assemblage of parcels with different owners in a holistic, united way. This is a great model for other multi-stakeholder, grassroots conservation and recreation projects.
University of Tennessee students identify winter creeper (Euonymus fortunei) and bush honeysuckle (Lonicera sp.) during a volunteer invasive plant mapping event on March 28, 2015 at River Bluff Park in Knoxville.
The first step of the Ecological Inventory was to map invasive plants throughout the Urban Wilderness. Because there was only a small amount of funding and staff support for this daunting effort, a creative solution was required. Citizen-scientists were recruited to conduct the surveys, using a mapping technique based on the methodology of the Early Detection and Distribution Mapping System. Volunteers who had experience with plant identification led teams of 2-4 University of Tennessee undergraduate students and other participants in mapping patches of invasive species in designated zones of the Urban Wilderness. Over six work days, a total of 85 different volunteers helped map almost 500 acres of land. The data are being entered into a geodatabase that will allow managers to see the spatial extent of different invasive species and begin to plan invasive plant removal and restoration projects. For example, information about where invasive plants occur will be used in planning a volunteer-based “Weed Wrangle” event in Knoxville in 2016. The geodatabase will also allow researchers to answer questions about why certain species may occur in particular areas.
In addition to creating valuable data that will be used to guide management, these citizen science events helped educate students about plant identification, invasive plant impacts, local ecosystems, and ecological survey methods. Many students said they had fun, and came back multiple days. Invasivore editor Sean Hoban attended, and reports, “I learned to identify invasive plants, and can now pass that skill on to others. I also learned firsthand that invasive species’ cover in our urban wilderness is very heterogeneous- some areas are invaded heavily while others are mostly native, and certain invasives do better in some places than others. Surveys like these can be the base for a lot of good invasive plant ecology work. I hope to participate again!”
The Ecological Inventory of Knoxville’s Urban Wilderness is a great example of how readers of this blog can be involved in studying and controlling invasive species. If you are interested to know more, please contact Emily Zefferman at email@example.com.
Knoxville’s Urban Wilderness is a recreational asset for local residents and visitors.
Periwinkle (Vinca sp.) is a beautiful but invasive plant that is prevalent in many areas of the Urban Wilderness. Photo credit: Wes Charlton