Jun 24

Managing invasive plants in Knoxville’s Urban Wilderness

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.

forest of invasives

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.

citizen science

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 ezefferm@utk.edu.


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

Jun 19

Friday Feast! June 19, 2015

Eating invasive species news and notes from around the internet!

Jun 05

Friday Feast! June 5, 2015

Eating invasive species news and notes from around the internet!

Jun 01

Lessons learned eating insects

Make eating insects awesome, not altruistic. This is the message presented by Ophelia Deroy of the University of London Centre for the Study of the Senses in the latest issue of Nature. Deroy explains that although eating insects has been praised as nutritionally and environmentally beneficial, and despite the fact that historical records show insects have long been represented in human diets (a practice that continues in some regions to this day), Western policies and perspectives have generally viewed consumption of insects not as novel, but rather nauseating. However, Deroy argues that to improve perceptions of eating insects, rather than emphasizing a socially-conscious lifestyle, eating insects will need to be made fun.

As I read Deroy’s article and chewed on the topic of eating insects, I began to wonder if similar strategies might benefit the consumption of invasive species. Indeed, at invasivore.org, we’ve promoted dandelions and purslane as “gateway” invasives that can be harvested from personal gardens as a fun way to enter the world of invasivory. Furthermore, the popularity of events such as lionfish derbies provide evidence that hunting exotic species can be great fun. Anecdotaly, adding an element of fun to the harvest and consumption of invasive species seems to be a recipe for success.

However, critics rightfully argue that eating invasive species must not be all fun and games. Unlike the case of eating insects as a sustainable source of protein, there is nothing to be gained from separating the act of eating invasive species with the ecological goals of reducing target populations and increasing overall awareness about biological invasions. Furthermore, decoupling the consumption of invaders and the goal of reducing their impact carries the substantial risk of encouraging invasive species desirability and cultivation, thereby further spreading harmful species. A successful overall strategy for managing invasive species requires that we keep biological invasions on our minds as well as on our plates.

Nevertheless, there are lessons about palatability and fun from eating insects that could benefit the current experiment in consuming invasive species (and likely similar mutually beneficial exchanges of ideas to be had between locavores and other eco-conscious food movements). However, not all movements have the same goals and challenges- a key factor to remember as lessons and data are exchanged between such experiments. Just as Deroy concludes in her discussion of consuming insects, the many various eco-conscious food movements will all benefit from cooperation between food scientists, chefs, psychologists, invasivores, locavores, and more.

Invasivore editors Matt and Andy enjoy mealworm Rice Krispies treats

Invasivore editors Matt and Andy enjoy mealworm Rice Krispies treats

May 29

Friday Feast! May 29, 2015

Eating invasive species news and notes from around the internet!

May 18

Genetics helps reveal invasion histories

(Text modified from Press Release from NIMBioS)

New tool could help in controlling biological invasions, such as the emerald ash borer, the Asian beetle which is now advancing on the East Coast after having wiped out up to 80 percent of ash trees in the Midwest. USDA

Asian carp. Hemlock woolly adelgid. Destructive pests that raise the hackles of fisherman, farmers, and wildlife managers everywhere they invade.

But how do they establish themselves and take over non-native species so effectively and efficiently?  Specifically, what is happening early on in invasions, before we take notice of them?

Knowing answers to these questions could help experts manage and control invasive species.  And genetic data from invasives can help reveal the answers.

In research from the National Institute for Mathematical and Biological Synthesis (NIMBioS) and the University of Ferrara, Italy, scientists have devised a new method for investigating the factors that contribute to biological invasions of non-native species.

In the new study, published in the journal Heredity, researchers used genetic data to analyze multiple waves of a single biological invasion. Tested on simulated data across a large range of realistic invasive situations, the study’s method was able to successfully use genetic data to correctly distinguish a two-wave invasion from a single-wave invasion. The method also correctly estimated the number of individuals that were introduced, and to some degree, the timing of introductions.  These are key variables of the early process of invasions that would be hard to know without genetic data, because invasions start small and sometimes take a long time to really get going.

Understanding these factors could advance ecological understanding of biological invasions, such as why many non-natives take a long time before rapidly increasing. Being able to differentiate between waves could also help in the management and control of them.  “Knowledge of whether second, or even third or fourth waves occurred in invading populations can help us better understand the dynamics of invasions. If second waves are common, managers could use this information to decide whether, how and when to isolate or eliminate small introduced populations,” said corresponding author and NIMBioS postdoctoral fellow Sean Hoban.

Prior to this work, some researchers had suggested it might not be possible to distinguish multiple waves from a single source. This study—the first to examine this type of invasion— shows otherwise.

In addition, the results have implications for plant and animal product inspection and interception of non-native species. According to the research, strict inspection could be important to continue even after first establishment to prevent further waves. For example, recent public messages from the Great Smoky Mountains National Park aim to prevent further waves of establishment of emerald ash borer by prohibiting people from bringing firewood into the park from outside.

In general, the authors emphasize that their approach could benefit much future invasive species work.

Citation: Benazzo A, Ghirotto S, Torres Vilaca ST, Hoban S. 2015. Using ABC and microsatellite data to detect multiple introductions of invasive species from a single source. Heredity. [Online]

May 08

Friday Feast! May 8, 2015

Eating invasive species news and notes from around the internet!

May 01

Friday Feast! May 1, 2015

Eating invasive species news and notes from around the internet!

Apr 24

Friday Feast! April 24, 2015

Eating invasive species news and notes from around the internet! 

Apr 17

Friday Feast! April 17, 2015

Eating invasive species news and notes from around the internet!

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