The tropical forests of Southeast Asia are famous for their rich biodiversity but are increasingly threatened by the growth of oil palm plantations. As the global demand for palm oil increases, the need for effective restoration practices in these areas becomes more urgent. A long-term study conducted by Göttingen University in Germany, along with IPB University and Jambi University in Indonesia, has looked into how ecological restoration can help recover biodiversity in oil palm plantations in Sumatra. Their results show that creating tree islands within extensive oil palm monocultures aids in the recovery of native tree species through natural regeneration. These findings were published in Science.
The international research team set up 52 tree islands of varying sizes and types of planted trees within a typical industrial oil palm plantation in Sumatra, Indonesia. This creative experimental approach offered valuable insights into how the initial choices made during restoration can impact biodiversity in areas dominated by oil palm. For example, conventional plantation practices often involve heavy use of herbicides and fertilizers to control undergrowth. Conversely, a variety of native species were able to successfully establish themselves in the tree islands, including trees that are unique to the Sundaland region. Within just six years, many of these trees have started to bear fruit, with some even reaching heights of over 15 meters. Notably, non-native species represented only ten percent of the natural regeneration observed in these restored areas.
The study emphasizes that tree islands facilitate the natural regeneration of native species, promoted by the arrival of seeds carried by wind or birds. This enhances both functional and evolutionary diversity, which are essential for creating resilient ecosystems that can endure climate change. Dr. Gustavo Paterno, a postdoctoral researcher at Göttingen University and the lead author of the study, states: “A key takeaway for plantation management is that larger tree islands, especially those covering over 400 m², are vital for endemic and forest tree species that find it difficult to locate suitable habitats in standard oil palm plantations.” He adds: “Increasing the area designated for restoration results in a surprisingly significant rise in diversity.”
The research revealed that starting with a greater diversity of native trees on each island can lead to a broader variety of ecological plant strategies taking root in the tree islands. “The more tree species you start with, the more functionally diverse the restored ecosystem will evolve over time,” explains Professor Holger Kreft, head of Göttingen University’s Biodiversity, Macroecology, and Biogeography research group. “Our study shows the potential for tree islands to convert biodiversity-poor agricultural areas into thriving ecosystems filled with diverse native plants.” However, the team also found that despite these positive outcomes, the biodiversity levels in the restored regions remain significantly lower than in untouched forests. This underscores the urgent need to protect existing forest patches, which hold invaluable conservation value.
This research was funded by the German Research Foundation (DFG) through the Collaborative Research Centre “Ecological and Socio-economic Functions of Tropical Lowland Rainforest Transformation Systems (EFForTS).”
