Recently the role of customary local institutions in the conservation of biological diversity has become a topic of widespread interest. In this paper the conservation value of one such institution, traditionally protected forest, is studied with regard to its ecological representativity and institutional persistence. On the basis of a case study from Mozambique the paper concludes that traditionally protected forests do have a practical conservation value, especially as fire refuges and in the preservation of metapopulations of endangered species. However, it (...) is also important to recall their spiritual aspect, which is crucial for their continuing appreciation and upholding. Even though customary institutions are still strong in the study area, they are subject to power struggles at both local and national levels. In the present context of political transition, any outside interventions regarding such local institutions as sacred forests, which have high symbolic value, should be considered carefully. (shrink)