Ecological features benefiting sustainable harvesters in socio-ecological systems: a case study of Swiftlets in Malaysia

A major challenge in biodiversity management is overharvesting by unsustainable harvesters. If a scenario could be created where sustainable harvesters benefit more than the unsustainable ones, even in the short term, the issue of overharvesting would be solved. Everyone would then follow the lead of sustainable harvesters. However, creating such a scenario is not an easy task; the difficulty is intensified if the habitat is open access and there is no property rights system. Swiftlets in Sarawak, Malaysia, present a special case where sustainable harvesters are believed to be more beneficial than unsustainable harvesters. Edible nests built by adult Swiftlets are used as ingredients for a traditional luxurious soup in Chinese cuisine. A rise in nest prices has increased the instances of unsustainable harvesters wrongfully collecting nests along with the eggs and fledglings, which are then abandoned. Swiftlets live in caves and build nests on cave ceilings. It is known that Swiftlets escape from cave ceilings when these harvesters take the nests, never to return to the same place. This ecological feature appears to work as the Swiftlet's indirect punishment against unsustainable harvesters. This study constructs a stage-structured population model and examines the effect of property rights and the indirect punishment by Swiftlets on the population dynamics of the bird, and on the economic return of both sustainable and unsustainable harvesters. Our findings are as follows: the indirect punishment by Swiftlets provides sustainable harvesters a higher short-term return than unsustainable harvesters under the property rights system, as long as Swiftlets return to their original cave after escaping from the unsustainable harvesters. While previous studies regarding the management of the commons have stressed the importance of rules and regulations for sustainable harvesting without considering the ecological uniqueness of each species, this study suggests that ecological exploration and the discovery of ecological features are also essential for designing a sustainable framework.