Sustainable harvesting of non-timber forest products based on ecological and economic criteria

1. Harvesting of highly valuable non-timber forest products (NTFPs) has been considered a win-win strategy where local people profit while conserving forest biodiversity ecosystem services. Nevertheless the sustainability of NTFP harvesting has been debated as the nature of NTFPs harvesting regimes scale of commercialization are highly heterogeneous, few studies have evaluated the cumulative ecological economic effects of such regimes. Here we assessed the medium-term (10 years) sustainability of NTFP harvesting using Chamaedorea palm leaves a major NTFP from Mesoamerica that is highly valued in the international floral industry as a case study. 2. We used an experimental ecological study and an economic assessment to analyse the sustainability of leaf harvesting in C. ernesti-augustii. A 4-year leaf removal experiment was conducted to assess effects of increasing levels of defoliation (0%, 25%, 50%, 75%, 100% leaf removal, biannually) on palm survivorship, leaf production and leaf quality. Results of this experiment were combined with estimations of harvest economic value to make projections of the availability of leaves and profit per unit area. Finally, we determined harvesting regimes that maximize profit while maintaining medium-term viability of exploited populations. 3. Palms tolerated up to 50% chronic defoliation, but higher defoliation levels reduced survivorship, leaf production and leaf quality. In the long term, this 50% defoliation level maximized harvest volume and profit without significantly affecting palm survival and leaf quality. Our results show that harvesters face the dilemma of either maximizing short-term income leading to rapid exhaustion of stocks, or maintaining exploited populations but maximizing income in the long term. 4. Synthesis and applications. Our study shows that intermediate harvesting levels (=50% leaf removal) are needed to achieve long-term sustainability of Chamaedorea palm leaves. Results of this study have an immediate application for the amendment of the official Mexican law, which enables higher harvesting intensities of Chamaedorea leaves, and for the design of sustainable management strategies. Applications of such strategies should consider communitybased management, fair markets, regulating norms, as well as a thorough communication among stakeholders. Key-words: Chamaedorea ernesti-augustii, defoliation, Mexico, plant demography, socioecological sustainability, tropical rain fores