The multipurpose tamarind (Tamarindus indica L.) tree is important for people’s livelihood and considered as sacred in the Mahafaly region of south-western Madagascar. However, the ongoing overexploitation of this species has caused a decline of tamarind trees. In this study, the species distribution, changes in tamarind biomass and the role of traditional taboos for the conservation of this species were determined to identify opportunities and constraints for its conservation and appropriate land management planning. Semi-structured interviews (N=63) were conducted in 10 villages in the study region to obtain information regarding the utilization of tamarind trees. During field surveys, the diameter at breast height (DBH), height, wood volume and wood biomass were measured for already felled trees (N=25). Additionally, 318 trees were inventoried by measuring their DBH, height and GPS location. Using high resolution satellite images from 2004/2005 and 2012 the crown areas of all tamarind trees in six village areas were identified. Allometric equations were established to predict their wood biomass from DBH, crown surface and wood volume. Tamarind trees are mainly used as supplementary food, as well as for traditional ceremonies, charcoal production and medicinal purposes. Altogether, 0.06–0.35 trees ha-1 were observed. A regression analysis yielded high coefficients of determination for the relationships between DBH and wood biomass (r2=0.98), DBH and crown area (r2=0.72), and crown area and wood biomass (r2=0.71). From 2004/2005 to 2012, wood biomass losses of 12%–90% were caused by charcoal production and slash and burn agriculture. The traditionally sacred status of the tree has become insufficient to secure its conservation in the Mahafaly region.