| Echinacea angustifolia DC. (Asteraceae), a medicinal plant native to North American prairies, has a 100 year history of commercial harvest in Kansas. Medicinal plants are increasing in economic importance, yet basic demographic data needed to assess the sustainability of harvest are unavailable for most wild harvested species. Methods used by harvesters and the response of plant populations to harvest are seldom incorporated into demographic studies to assess the impact of harvesting. Echinacea provides a good example for testing such a combined approach to the study of medicinal plant harvesting because of its economic importance, long history of harvest, and concern for its conservation.; Ethnobotanical and historical information are combined with demographic data and modeling to assess the potential of Echinacea angustifolia populations to sustain commercial harvest. Harvest levels are moderate, as harvesters appear to use an optimal foraging strategy to maximize hourly yield of Echinacea roots. Populations appear to be resilient: 25–35% of the plants regrow after harvest, areas with long history of harvest still support E. angustifolia populations, and market demand is cyclical, allowing time for populations to recover from harvest.; Demographic models, presented as size-structured population projection matrices, show that E. angustifolia populations are approximately stable without harvest. Differences among both sites and years in populations' density, recruitment, and growth rate may be influenced by land management and climatic fluctuation as well as past harvest. Deterministic, density independent projections and stochastic, density dependent projections both predict that the annual rate of harvest that may be sustained by E. angustifolia populations is low. Harvest should not exceed 5% of the harvestable sized plants annually. Harvesters' practice of digging a higher proportion of plants and allowing the stand to recover for two or more years appears to be economically and ecologically viable. However, unregulated commercial harvest over long periods of high demand cannot be sustained and is predicted to lead to local extinction. Conservation measures for E. angustifolia include restoration and management, cultivation, and harvest restrictions by private landowners and public land managers. |
