Rapid inventory of wild medicinal plant populations in Sri Lanka

Abstract

Sustainable use of wild populations of medicinal plants (as with other non-timber forest products) requires robust assessment of the distribution and abundance of target species. Long-term population dynamics datasets are typically unavailable in many developing countries, and then perhaps only for one to few high profile taxa. Given the scale and urgency of sustainability issues, one-off inventories provide the only realistic means for assessing the population status and harvest potential of assemblages of target resource species. Quantitative examples of such assessments are very rare, and limited in scale. As part of a national programme focusing on developing sustainable usage of medicinal plants in five biogeographically representative Medicinal Plant Conservation Areas (MPCAs) in Sri Lanka, we describe the rapid appraisal methodology developed for, and substantive results derived from, a resource inventory undertaken at respective MPCAs to provide: (a) baseline assessment of the distributions, associated population structures and densities, and ecological requirements of medicinal plant species; and (b) an informed basis for ongoing in situ conservation, management, and harvest sustainability of defined priority medicinal plant species. The applied methodology comprised: (a) quantitative assessment of medicinal plant populations and habitat features at 898 inventory plots, located using a strict hierarchical stratification; (b) standard numerical classificatory procedures to define major habitat types; and (c) areal estimates of habitats based on available fine-scale topographic mapping, augmented with refined mapping derived from Landsat TM imagery. Over 1400 medicinal plant species (ca. 40% of the national flora) were sampled during the inventory, occurring in habitat conditions ranging from dense-canopied, relatively undisturbed tropical forest, to savanna. Most vegetation was of a secondary nature reflecting ancient and varied histories of chena (slash and burn) cultivation, grassland/savanna burning for pastoral purposes, and recent logging. Medicinal plant species density was significantly correlated overall with higher rainfall, higher elevation, deeper and more acid soils. Derived population estimates and structures, and the potential for sustainable harvest from the wild, are assessed for 34 priority medicinal plant species. Results demonstrate the very low resource base of most priority species, and the varied habitat and disturbance requirements of medicinal plants in Sri Lankan reserves. It follows that (a) greater attention needs to be given to ex situ propagation and farming of medicinal plant resources—although for many long-lived perennial taxa this is likely to be impractical; (b) there can be no one management prescription which caters for all component species; and (c) for effective conservation local communities need to be actively involved in managing natural vegetation habitats (albeit under regulated conditions), including imposition of various forms of small-scale disturbances such as harvesting and, where appropriate, fire management.