A framework for considering ecological interactions for common non-timber forest product species: a case study of mountain date palm (Phoenix loureiroi Kunth) leaf harvest in South India

Abstract

Many economically important non-timber forest products (NTFPs) come from widespread and common plant species. Harvest of these species often is assumed to be sustainable due to their commonness. However, because of the ecological roles of common species, harvest may affect and be affected by ecological interactions at broader scales, which are rarely considered when evaluating the sustainability of harvest. We use a case study of the mountain date palm (Phoenix loureiroi Kunth), harvested in South India to produce brooms, to present a conceptual framework illustrating how intensive harvest of a common species interacts with other anthropogenic management practices, plant-animal interactions and surrounding environmental conditions. We apply this framework to understanding the impacts of mountain date palm harvest in the southern Western Ghats regions of the Indian states of Tamil Nadu and Karnataka. We integrate data on the extent and levels of commercial harvest, local management practices, the ecological context in which harvest occurs, and research on harvest effects. We use this information to document the intensity and extent of mountain date palm harvest in the study area, identify the ecological implications of harvest, and demonstrate how a framework that considers harvest in the context of ecological communities and ecosystems is important for assessing the impacts of harvest of common NTFP species. We show that mountain date palm leaves are heavily harvested from natural areas in the southern Western Ghats but that harvest levels have declined in recent years. Mountain date palm management and harvest occur within a network of ecological interactions, linking human activities to population-, community-, and ecosystem-level processes. We demonstrate that understanding the effects of return interval of anthropogenic fire, herbivory by wild animals and livestock, as well as the light environment in which harvest occurs are critical to assessing the sustainability of mountain date palm harvest. By considering mountain date palm leaf harvest in the context of ecological interactions at multiple scales, our findings show that sustainability cannot be assessed only from a population-level perspective. This general framework highlights the need to incorporate ecosystem- and community-level properties and processes more frequently into assessments of the sustainability of NTFP harvest—especially for widespread and common species—to ensure that their important economic and ecological roles are maintained.