Protecting wild populations and working landscapes: the case for transitioning to size-based criteria for federal regulation of American ginseng

Abstract

Overharvesting of wild medicinal plants threatens biodiversity, rural livelihoods, and the long-term sustainability of harvested populations worldwide. Wild American ginseng (Panax quinquefolius L.) is listed on appendix II of the Convention on International Trade in Endangered Species and, as a result, is regulated in the United States under a federally coordinated, age-based harvest framework intended to sustain natural populations. However, age-based criteria assume strong, consistent relationships between plant age, size, and reproductive capacity—relationships that do not hold up for many other plant and animal species, and have been questioned for American ginseng. We test whether size-based metrics provide a stronger and more practical basis for regulating ginseng harvest than chronological age. We measured age, aboveground traits, root biomass, and reproductive output for wild-simulated ginseng plants (5–10 years old) across four sites spanning substantial environmental heterogeneity. Leaf area, estimated from a simple field measurement, explained 75% of the variation in root dry mass, far exceeding the explanatory power of age (12%) or the combination of age and leaf count (36%), representing the current regulatory approach. Leaf area also strongly predicted the probability of reproduction and maximum seed production, with larger plants consistently outperforming smaller individuals, regardless of age. Our results demonstrate that age-based harvest criteria are weak proxies for the biological attributes most relevant to conservation and sustainability. A simple, field-measurable size metric better reflects ginseng performance and could underpin a transition to size-based regulation, analogous to widely used approaches in fisheries management.