Population, Distribution, and Threats of American Ginseng (Panax quinquefolius L.) in Indiana and Illinois

Oliver, Leah, Amanda Treher, and Anne Frances. NatureServe, Arlington, VA. leah_oliver@natureserve.org

(Presented at The Future of Ginseng and Forest Botanicals Symposium, July 12-14, 2017, Morgantown, WV)

Abstract

American ginseng, Panax quinquefolius L., is one of the most iconic medicinal plants in North America. Although ginseng has been continuously collected over hundreds of years, more than a decade of research shows that it is currently facing increased threats from wild harvest, herbivory, and climate change. These increased threats have recently raised concern about ginseng’s conservation status and sustainable harvest practices. Indiana and Illinois are each one of the top ten states with the greatest legal export. In addition, large-scale illegal wild collection of ginseng root was recently documented from these states. Working collaboratively, botanists from NatureServe, the Indiana Natural Heritage Program, the Illinois Division of Forest Resources, independent companies, and the U.S. Geologic Survey collected current population and genetic data for ginseng in Indiana and Illinois in 2016. A total of 65 sites across 42 counties were surveyed; most sites were impacted by one or more threats, and many populations are considered small. Demographic data revealed that many populations had a higher ratio of juvenile plants to mature plants than expected. The observed pattern suggests harvest pressure, since most well-established ginseng populations have more mature plants than juvenile plants. Results from this study will inform the conservation status of ginseng in these states as well as nationally and globally, and inform future conservation efforts. The forthcoming genotype results will clarify whether the sampled ginseng plants originate from local or non-local seed sources.

Keywords: conservation, threats, Indiana, Illinois, demography, harvest, wild simulated seed, medicinal plants, NatureServe

Introduction

American ginseng (Panax quinquefolius L.) is native to forests in the eastern United States. Ginseng is a widespread species that has been continuously harvested for its medicinal use for hundreds of years. Despite having a large range with many occurrences, NatureServe considers American ginseng to be Globally Vulnerable (G3) to extinction, primarily due to numerous threats and a declining trend (2005). The direct and indirect consequences of harvest are of great concern for the conservation of the species. Wild-collected ginseng is harvested throughout its range for export to international markets; however, collection is illegal in Canada. Among U.S. states, Indiana ranks 5th and Illinois ranks 8th in the amount of ginseng harvested for export.

Knowledge of a species’ distribution and the health of its populations are fundamental to assessing its extinction risk. Assessing the conservation status of native plants, animals, and ecological communities is central to the NatureServe Network’s mission. The NatureServe network, a partnership of 80 natural heritage programs or conservation data centres across North America, conducts field surveys of species’ populations which are used to evaluate the extinction risk or conservation status of each species. Conservation status assessments are conducted at subnational (state or provincial), national, and global scales, with a ranking system indicating the relative level of imperilment on a scale from one to five (Faber-Langendoen et al. 2012). These ranks are used by government agencies in the United States and Canada to prioritize species for conservation.

Rarity, threats, and trends are the three factors that underpin conservation ranks. Rarity is generally quantified through population size and number of occurrences, both of which are obtained through field surveys. While ginseng has a broad distribution comprised of many populations, research suggests that ginseng populations have been steadily decreasing. Documented threats to ginseng populations throughout its range include harvest pressure, deer herbivory, and habitat degradation. However, the impact of threats on ginseng has not been comprehensively evaluated throughout its range.

The impact of certain harvesting practices on ginseng populations is a significant conservation concern. Most collectors follow the long-honored tradition of leaving seed in harvested populations, which ensures future harvest. The concern is not over the practice of leaving seed behind, but rather the source and geographic origin of the seed being planted. Rather than leaving seed from the original population during harvest, collectors sometimes leave ‘wild-simulated’ seed instead. Wild-simulated seed originates from farmed populations typically grown in Wisconsin. Mixing wild-simulated seed with true wild populations can decrease the genetic vigor of the true wild populations. This is because introducing genes that are not adapted to local environmental conditions can reduce a population’s ability to adapt to those conditions. If the practice of using wild-simulated seed is occurring on a large scale, it could impact ginseng’s long-term viability.

In Indiana and Illinois, the state ranks (Sranks) indicate that ginseng is vulnerable, ranked S3 and S3?, respectively, though the Sranks have not been reviewed in more than 15 years. An S3 indicates that a species is vulnerable due to a restricted range, relatively few populations or occurrences, recent and widespread declines, or other factors making it vulnerable to extirpation (Master et al. 2012). The goals of this project were 1) to collect current population data on Panax quinquefolius in Indiana and Illinois to inform the conservation status ranks for these states, and 2) to gather genetic samples that will inform studies on the impacts of wild simulated seed. Genetic samples were collected to leverage funding for the field surveys, but additional funding is needed to process the samples.

Methods

We surveyed 37 sites in Indiana and 28 sites in Illinois from August to October of 2016. Given the time and resource limitations, we focused on sites documented having robust ginseng populations in the past, and that represent wide geographic areas within each state. Site selection was a highly collaborative effort with the Indiana Natural Heritage Program, the Illinois Ginseng Coordinator, and field biologists. We obtained necessary permits and permission to access all sites.

We surveyed populations to determine whether ginseng met the description of S3 as follows: “vulnerable … due to a restricted range, [with] relatively few populations or occurrences, recent and widespread declines, or other factors making it vulnerable to extirpation” (Master et al. 2012). We collected site information including name, ownership, geographic coordinates, habitat characteristics, and associated species. The Indiana Special Plant Survey form was used at each site in both Indiana and Illinois (Appendix 1).

We collected data on ginseng populations such as phenology, number of individuals, population extent, and age class. We documented age classes according to how many palmately compound leaves, or ‘prongs’ were observed on an individual plant. Plants with a single stem and three leaflets were categorized as seedlings, plants with one to two prongs were categorized as juveniles, and plants with three to four prongs were categorized as adults. Although seedlings were noted at some sites, these data were not consistently collected throughout the study because it was difficult to distinguish ginseng seedlings from other similar looking species.

Threats to ginseng were recorded and described in field forms. Threats were recorded at all sites, even when ginseng was not found. At sites where ginseng was absent, herbivory was recorded when other plant species at the site were disturbed. Wild collection was documented through evidence of freshly dug holes and other human disturbances around plants, (e.g., flagging, litter, paths). In some cases, wild collection was documented by law enforcement officers or landowners with recent first-hand reports of poachers digging ginseng at study sites.

We categorized small populations as those with 20 individuals or fewer, based on a study by Souther and McGraw (2014) that calculated 20 individuals to be the quasi-extinction value within 70 years. Using population viability analyses, the study detected genetic degradation and population decline leading to extinction in populations of 20 or fewer individuals. For this study, using a threshold of 20 individuals to categorize populations as small is conservative considering that many of these populations are predicted to become extirpated within a short timeframe.

Genetic samples were collected using Whatman FTA™ plant saver cards following a protocol designed to capture genetic material from leaves with minimal damage to the plants (Young 2014). FTA cards allow genetic material to be transferred from the leaves and fixed to the cards for long term storage. FTA cards were placed in plastic bags with desiccant and stored in the freezer.

Results

Ginseng was present at 22 of 37 sites in Indiana and 25 of 28 sites in Illinois (Fig. 1). In Indiana, there were 8 populations with 1-20 plants, 10 populations with 21-50 plants and 4 populations with 51-165 plants.  In Illinois, there were 14 populations with 1-20 plants, 20 populations with 21-50 plants, and 13 populations with 51-165 plants. There were 15 sites in Indiana, and 3 in Illinois where surveyors failed to find ginseng. The timing of the surveys coincided with the beginning of senescence of ginseng plants, so it is possible, though unlikely, that early senescence led to an overestimate of sites where surveyors failed to find ginseng. Of the inventoried sites with ginseng present, 29% were represented by small populations, as defined by 20 or fewer plants.

Invasive species and herbivory were the most pervasive threats (Fig 2). Invasive species were present at 68% of sites in Indiana and 80% of sites in Illinois. The most frequently encountered invasive species were Lonicera mackii (Japanese honeysuckle), Rosa multiflora (Multi-flora rose), and Alliaria petiolata (Garlic mustard). Herbivory by deer or rabbits was observed at 73% of sites in Indiana and 44% of sites in Illinois. Insect damage was observed on many plants but only appeared to cause superficial damage. Wild collection was documented at 5% of sites in Indiana and at 24% of sites in Illinois (Fig 2).

Fig 1. Sites surveyed in Indiana and Illinois in 2016. American ginseng was present at 22 of 37 sites in Indiana and 25 of 28 sites in Illinois. Circle size indicates population size with small circles indicating populations with 20 individuals or fewer, medium circles with 21 to 50 individuals, and large circles indicate populations of greater than 51 individuals. Empty plus symbols indicate sites where surveyors failed to find ginseng (18).

Fig 2. Threats to sites surveyed for ginseng. Invasive species are the most common threat, followed by herbivory. Wild collection was observed at more sites in Indiana (a) than Illinois (b) where ginseng was present.

We analyzed population demography of sites with more than 20 individuals. Of these, we found that 38% of sites in Indiana and 56% of sites in Illinois were comprised of more than 50% juveniles (Figs. 3 and 4). While results from both states indicate high numbers of juveniles within each population, more populations in Illinois had high numbers of juveniles in populations compared to Indiana (Figs. 3 and 4).

Fig 3. Population demography of 13 sites in Indiana with more than 20 plants. White indicates the percentage of juveniles (1 and 2 pronged plants) and black represents the percentage of mature individuals (3 and 4 pronged plants).
Fig 4. Population demography of 18 sites in Illinois with more than 20 plants. White indicates the percentage of juveniles (1 and 2 pronged plants) and black represents the percentage of mature individuals (3 and 4 pronged plants).

Discussion

The primary objective of this study was to survey ginseng populations in Indiana and Illinois to inform the conservation status of the species in those states. Although limited by a one-time, single visit to each site, we were able to summarize threats, estimate population demography, and identify potentially extirpated sites. Here we relate the results of this study to ginseng conservation throughout its range, focusing on the main factors impacting ginseng population health in Indiana and Illinois. We found that ginseng is significantly threatened by herbivory, invasive species, and potentially unstainable harvest. Nearly 30% of populations in this study were considered so small (20 or fewer individuals) that they are expected to be extirpated within the next 70 years. Many populations were comprised of higher percentages of juveniles than adults suggesting the effects of harvest pressure. Lastly, while this study did not measure trends, it is noteworthy that ginseng was not present at 18 sites where it was previously known.

Threats are a key factor in determining a species’ risk of imperilment in both NatureServe’s and the IUCN Red List’s conservation status assessments (Master et al. 2012, IUCN 2017). In this study, invasive species and herbivory were the predominant threats. Invasive species were pervasive at most field sites in both Indiana (68%) and Illinois (80%). Similarly, Wixted and McGraw (2008) documented invasive species at 63-70% of ginseng populations surveyed across multiple states. Rosa multiflora was the most frequent invasive species encountered in this study as well as in the Wixted and McGraw (2008) study. Another commonly encountered invasive was garlic mustard (Alliaria petiolata). The presence of garlic mustard has been associated with increased ginseng mortality, perhaps due to allelopathy (Wixted and McGraw 2009). It is highly likely that invasive species are negatively impacting ginseng in Indiana and Illinois by altering landscape condition and degrading habitat.

Herbivory was documented at most sites surveyed in both Indiana and Illinois. This is not surprising as deer-browse is considered a widespread threat to ginseng (McGraw et al. 2013). While herbivory does not immediately kill plants, it does cause decline in population growth over time (Farrington et al. 2009, McGraw and Furedi 2005). Using life history models, Farrington et al. (2009) predicted that deer-browse alone would decrease ginseng’s population growth rate by 2.9% over 7 years. In West Virginia, deer-browse resulted in a 2.7% decline in ginseng populations (McGraw and Furedi 2005). Based on the high percentage of deer-browse in Indiana in this study (73% of sites), it is likely that herbivory has contributed to declines in ginseng population growth. While deer-browse was less frequent in Illinois (44% of sites), it is also likely to be contributing to declines in ginseng population growth.

Wild collection or harvest was documented at 24% of Illinois and 5% of Indiana sites where ginseng was present. Wild collection was documented at each site based on the observation of freshly dug holes and reports from conservation officers. However, documenting this threat based on one site visit was challenging. All our field surveys took place in late summer and early fall, coinciding with the start of the ginseng harvest season. Harvest that occurred after our surveys was not documented in this study. Interpreting the wild collection in this study would require more information on the factors impacting collection such as timing of field work in relation to harvest and differing harvesting regulations by state.

Population size and demography

We documented many small populations in both Indiana and Illinois. This result is consistent with previous research indicating that most naturally occurring ginseng populations are less than 150 individuals (McGraw et al. 2013). Small populations are of conservation concern because they are at greater risk of extirpation. Once ginseng populations are reduced to 20 individuals they are considered quasi-extinct because Allee effects and demographic stochasticity lead to population degradation (Souther and McGraw 2014). In their study, Souther and McGraw (2014) also found that population extinction risk was 65% when populations of 140 plants were threatened by climate change and harvest.  If we assume that small populations will eventually become extirpated (per Souther and McGraw (2014), nearly 30% of the sites surveyed in the present study will not persist over the next 70 years. Even the largest population in this study (165 individuals) would be considered small in the context of long-term viability, based on ginseng population viability models. For example, one population viability model showed that 172 ginseng plants are needed to maintain a population for the next 100 years, considering stochastic events (McGraw et al. 2013). Another study from West Virginia concluded that 800 individuals are required for a population to remain extant for 100 years under current deer browsing pressure (Furedi and McGraw 2005). Based on the threats documented for Indiana and Illinois, most populations surveyed in this study would not be expected to persist for more than 100 years.

Many populations had a high proportion of juvenile to adult plants, a pattern connected with overharvest. In Indiana, 38% of sites and 56% of sites in Illinois were comprised of more than 50% juveniles. The demographic pattern detected in this study was coined as the “fingerprint” of harvest pressure by Mooney and McGraw (2009), substantiated by other studies. For example, a study by Sanders-Cruse and Hamrick (2004) concluded that harvested ginseng populations in had a higher ratio of juvenile to adult plants than ginseng populations protected from harvest through regulations. The reduction of reproducing adults leads to a decline in population growth and regeneration. If this is repeated over many growing seasons, populations will ultimately decline.

The observed demographic pattern of a high number of juveniles shows harvest-induced evolutionary change, one that mirrors exploited fish stocks (Mooney and McGraw 2009). Data collected by the U.S. Fish and Wildlife Service for CITES (Convention on International Trade of Endangered Species of Wild Fauna and Flora) show a decrease in the mass of harvested ginseng roots over time (Mooney and McGraw 2009). Harvest induced evolutionary changes in ginseng could result in a reduction in the size of mature plants since diggers often harvest larger plants. We observed the same demographic pattern in Indiana and Illinois, indicating that perhaps harvest-induced evolutionary change leading to smaller mature plants is occurring in Indiana and Illinois.

Acknowledgements

This project would not have been possible without the efforts of Cary Floyd, Indiana Ginseng Coordinator; Paul Diezman, Illinois Ginseng Coordinator, Shawna Meyer, Principal for Natural Resource Insight Inc.; Robert Jean, PhD, Senior Entomologist, Environmental Solutions and Innovations, Inc. and Amanda Treher, Research Botanist, NatureServe who worked together to identify and inventory field sites. We acknowledge Ron Hellmich, Coordinator for Indiana Heritage, for his support in the site selection process, and for acquiring the FTA plant cards needed for the plants in Indiana. Kudos go to United Plant Savers who generously funded the FTA plant cards for Illinois. We are grateful to John Young and Tim King of US Geologic Survey for providing the protocol for collecting genetic samples. We regret that Tim King passed away unexpectedly during the study and will not be able to learn of the results of the study. Pat Ford and Rose Gnam of the US Fish and Wildlife Service provided invaluable support throughout the duration of the study. Finally, this study was generously supported by the National Fish and Wildlife Association, Impact Directed Environmental Accounts (IDEA) program.

Appendix 1:  Indiana Special Plant Survey Form

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