Making business scents: how to harvest incense sustainably from the globally threatened lansan tree Protium attenuatum
2015
Daltry, Jennifer C. | Prospere, Alfred | Toussaint, Adams | Gengelbach, Jana | Morton, Matthew N.
Wild tree resins generate billions of dollars in revenue annually but many species face extinction. The lansan tree Protium attenuatum has disappeared across most of its range as a result of overexploitation for its valuable oleoresin, which is used as incense. This study in Saint Lucia aimed to determine whether lansan resin could be harvested sustainably. Over 34 months, 298 trees were tapped using 10 experimental methods, and compared with 74 controls. Significantly more resin was produced by tapping the same trees repeatedly, tapping trees with a wider girth, cutting the same part of the trunk repeatedly, and, in particular, spraying diluted sulphuric acid on the cut. Applying 5 and 30% sulphuric acid boosted yields by 58 and 134%, respectively, without negative impacts on tree growth, condition or mortality. In contrast, traditional methods used by local tappers were destructive, causing greater decay and infection, slower growth rates and increased mortality. Results show tappers can obtain more resin and maintain healthy populations by tapping mature trees of ≥ 20 cm diameter at breast height, using only one shallow cut per tree (refreshed every 2 weeks) and applying weak sulphuric acid solution. A blind survey found consumers could not distinguish between incense produced with or without this stimulant. A national management plan has been devised whereby tappers will be licensed and trained in the optimal method and granted their own forest coupes to manage under Forestry Department supervision. The methods and findings may guide the sustainable use and conservation of other resin-producing trees.
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