Effects of rubber cultivation on biodiversity in the Mekong Region.

Abstract In the Mekong Region, the expansion of rubber plantations is a major threat to the remaining natural forests and has led to a considerable degradation of biodiversity. The shift from traditional agriculture to rubber cultivation additionally reduced landscape and agricultural system diversity and with this, the availability of potentially useful habitat types for species originating from natural forest. In most cases, monoculture rubber plantations showed to harbour less than half of the species richness in various plant and animal groups compared with natural forest, and often it was found or being assumed that many of these species are unable to exist permanently in rubber plantations. There is clear evidence that the existence natural forest area is essential for the conservation of large portions of native forest species in rubber-dominated landscapes. Alteration of rubber monoculture land use can only contribute effectively to species conservation if natural forest plots remain. Furthermore, suggested restoration concepts such as the conversion of rubber plantations into forest on marginal sites and land-sharing approaches are currently only vaguely described, and their contribution to the conservation of native forest species remains uncertain. In addition, modalities of stakeholder involvement, economic compensation and ecologically reasonable implementation of such measures are still unexplained. As an ecologically reasonable and economically feasible method to improve species diversity in rubber monoculture plantations, we suggest the promotion of natural undergrowth vegetation to enlarge suitable habitat structures in connection with natural forest. This can be reached through the cease of weeding and herbicide application and potentially through the cultivation of useful wild plants.