Reviewing Oil Palm Agroforestry Research – Group Activity

EFForTS BEE Results – Sub-Group B One Year After Establishment^[10]

Gérard et al.^[10]: Oil-palm yields in diversified plantations: Initial results from a biodiversity enrichment experiment in Sumatra, Indonesia

Overall, EFForTS BEE researchers found an initial increase in the oil palm yields inside the experimental plots and positive spillover effects for the yields of oil palms closest to the plots. They also found that although one would expect losses from the removal of oil palms, there is no significant trade-off – at least not during the initial phases of the biodiversity enrichment experiment.

Gérard et al.^[10]state – referring to other studies – that the increased yields are most likely associated with the thinning of oil palms, which leads to better lighting conditions, access to water and nutrients for the oil palms. However, the results also showed that thinning alone would not lead to a net-positive outcome and other factors are also involved. On the one hand, it is also discussed that, as other trees grow taller, the competition between the different tree species and the oil palms might reduce the oil palm productivity. On the other hand, further studies show that such tree enrichment measures can improve the ecosystem functioning within the oil palm plantation. The resulting diversification of crops could improve food security for the local people and make the local economy more resilient to changes in the environment or the global economy.

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Figure 13: These box-plots highlight the economic evaluation of the net yield changes that are the result of the experimental treatment. For their evaluation Gérard et al. calculated the estimated sum of the increased yield of oil palms inside and adjacent to plots and then subtracted the losses caused by thinning (meaning: increased yield inside plots + increased yield adjacent to plots – yield losses from thinning). The results are then shown for each of the differently sized experimental plots (X-Axis). The dashed line in this case symbolizes a net yield gain/loss of zero. The black bold line in each box again represents the median, while the “+” symbolizes the mean value.

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