Simulation of rattan harvests in Indonesia : different harvesting pressures and the resulting patterns

Sammanfattning: The objectives of this research were to determine whether the natural rattan resources in Sulawesi, Indonesia can cope with the strongly increased harvesting pressure that has occurred over the last centuries. I was furthermore looking for patterns in the rattan population dynamics that might give a hint on how the harvesting system could be improved to ensure a maximum sustainable yield. To answer these questions, I developed an individual-based model to analyse the dynamics of rattan growth in connection with rattan harvests by locals to identify sustainable levels of rattan harvests around villages in Sulawesi, Indonesia. Scenarios with different harvesting intensities were run to compare the change in harvest amount. For a given harvesting pressure, scenarios with a high number of harvesters and a low harvesting frequency had the same effect as scenarios with high harvesting frequencies and a low number of harvesters. Scenarios with a high harvesting pressure led to a rapid decline of the harvested rattan amounts. Simulations showed that a maximum sustainable yield can be obtained as long as a harvesting pressure of 1.13 harvesting actions per month in an area of 7.07 km2 was not exceeded. Comparing the current harvesting situation with the different scenarios from the model, a long-term sustainable harvest seems unlikely, especially when considering that there is an increasing worldwide rattan demand, for which specialized rattanharvesting groups intensify their harvesting actions. To avoid further overexploitation of Indonesia’s rattan resources there is a need to manage rattan harvests.