Biodiversity in oil-palm plantations is approximately half that of nearby tropical rainforests, reports a study published this week in Nature Communications. Understanding how ecological communities change when natural habitats are cleared for agriculture could help identify ways to maximise both the commercial and ecological value of land.
Clearance of rainforests to make way for commercial oil-palm plantations is one of the most rapid sources of land-use change in the tropics. The extent to which these changes affect biodiversity is not well understood, but they are predicted to negatively affect the overall functioning of ecosystems. One way of assessing this is by measuring metabolic energy flow. Metabolic energy refers to the caloric energy that flows through an ecosystem, often beginning with solar energy absorbed by plants, which is transported to the herbivores that eat them and then on to apex predators, before ending with decomposers such as bacteria. While some loss in metabolic energy is expected (for example when energy is converted to body heat and radiated away), a large loss of energy indicates a reduction in the functioning of the ecosystem.
Ulrich Brose and colleagues sample invertebrate communities among different land-use types in Indonesia and find that oil-palm plantations are less biodiverse than commercial rubber tree plantations, and contain around half the number of species when compared to natural forests. Calculating metabolic energy flow within each habitat, the authors also find that the efficiency of oil-palm food webs is less than half of natural forests. This indicates that species loss can lead to a direct and proportionate loss in the functioning of an ecosystem. Although rubber tree plantations also displayed reductions in energy flow, the authors suggest that commercial exploitation of this resource presents a more ecologically valuable use of forest land for commercial purposes.