Ecological measures are not necessarily at the expense of yield: tree islands in palm oil plantations can increase biodiversity without reducing productivity over the entire area. This emerges from the results of a long-term test on the Indonesian island of Sumatra. Despite this economic opportunity for ecological upgrading, protection against further deforestation remains the top priority, the scientists emphasize.
Frying oil, cosmetics, energy sources... The golden substance from the pulp of the oil palm is suitable as a basis for the manufacture of many products. This led to an enormous cultivation boom: palm oil plantations now cover around 21 million hectares of our planet. In Southeast Asia in particular, huge areas of forest were transformed into monocultures. Where orangutans and co once shimmyed their way through species-rich natural paradises, hardly anything else grows now than the palm tree, originally from Africa. “Most ecological studies of palm oil are limited to noting biodiversity loss and ecosystem degradation. Our approach now goes one step further," says senior author Holger Kreft from the University of Göttingen.
Oases in monoculture
In order to find out to what extent the negative effects on the environment can be mitigated through ecological upgrading, he and his international colleagues have launched a long-term project: On the area of a 140-hectare oil palm plantation on the island of Sumatra, they have 52 tree islands of a medium size planted of 400 square meters. These mixtures of up to six local tree species and a few oil palms stood on a total of 2.4 hectares of the test area. In addition, the undergrowth in the tree islands was able to develop freely.
Over several years, the scientists analyzed how the tree islands affect the biodiversity of insects and other invertebrates, as well as plants, birds and bats. They also studied soil microorganisms and the effects of the tree islands in relation to ecosystem services, such as the regulation of material cycles and the microclimate. As might be expected, more of these natural entities favorably affected the factors studied. Accordingly, tree islands lead to a significant ecological upgrading of palm oil plantations by leading to more biodiversity and improved ecosystem services.
Ecologically and economically favorable
What was surprising, however, was the economic finding. Because the researchers had actually expected that the yields would deteriorate because the tree islands would have used up resources for their own development at the expense of the oil palms. The bottom line, however, was that this effect did not occur over the entire area, as the researchers were able to determine by working together with the operators of the plantation: Within five years, the tree islands increased the biodiversity of the farm without reducing the oil yield. Apparently, the oil palms were able to benefit from the favorable effects of the tree islands to such an extent that losses at the overall level in the plantation were offset.
“Our results show that industry can benefit from this measure. There is real potential to develop these ecological restoration practices on a large scale,” concludes lead author Delphine Clara Zemp from the University of Neuchâtel. Kreft continues: “Our approach is unique in the world because it takes place on a large scale against the backdrop of industrial-scale oil palm plantations. Now we can determine the optimal composition and size of the islands that will produce the best possible ecological recovery," says Kreft.
"On the basis of the work, guidelines for certification could also be developed," says co-author Ingo Grass from the University of Hohenheim. "This would give consumers a choice here in Europe too and they could use their market power to make palm oil cultivation more sustainable," says the researcher. In conclusion, however, the team emphasizes that avoiding deforestation continues to have top priority: "The encouraging results must not lead to the conservation of tropical forests, which are home to irreplaceable biodiversity, being endangered," the scientists warn.
Source: University of Göttingen, University of Hohenheim, specialist article: Nature, doi: 10.1038/s41586-023-06086-5