Oil palm agriculture has become one of the economic mainstays for biodiversity-rich countries in the tropics. The conversion of native forests to oil palm monoculture plantation has caused unprecedented biodiversity loss in Southeast Asia. Little is known about the effects of oil palm polyculture farming on arthropod diversity. In this study, arthropods were sampled using pitfall traps at 120 sites in Peninsular Malaysia. We examined how arthropod biodiversity responded to different oil palm farming practices and local-scale vegetation structure characteristics. We found that the number of arthropod orders was significantly greater in polyculture than monoculture smallholdings. However, we did not detect a significant difference in arthropod order composition nor abundance between monoculture and polyculture practices. In situ habitat characteristics explained 16% of the variation in arthropod order richness, with key predictor variables including farming practice, height of oil palm stands, and number of immature palm. The findings of this study suggest that polyculture farming together with management for in situ habitat complexity may be a useful strategy in supporting biodiversity within in oil palm plantations.

No abstract

Monoculture farming is pervasive in industrial oil palm agriculture, including those RSPO plantations certified as sustainably managed. This farming practice does not promote the maintenance of farmland biodiversity. However, little scientific attention has been given to polyculture farming in oil palm production landscapes. Polyculture farming is likely to increase the floristic diversity and stand structural complexity that underpins biodiversity. Mist nets were used to sample birds at 120 smallholdings in Peninsular Malaysia. At each site, 12 vegetation structure characteristics were measured. We compared bird species richness, abundance, and composition between monoculture and polyculture smallholdings and used predictive models to examine the effects of habitat quality on avian biodiversity. Bird species richness was significantly greater in polyculture than that of monoculture smallholdings. The number of fallen and standing, dead oil palms were also important positive predictors of species richness. Bird abundance was also strongly increased by standing and dead oil palms and decreased with oil palm stand height. Our results indicate that polyculture farming can improve bird species richness in oil palm production landscapes. In addition, key habitat variables that are closely associated with farming practices, such as the removal of dead trees, should and can be managed by oil palm growers in order to promote biodiversity. To increase the sustainability of oil palm agriculture, it is imperative that stakeholders modify the way oil palms are currently planted and managed. Our findings can guide policy makers and certification bodies to promote oil palm production landscapes that will function more sustainably and increase existing biodiversity of oil palm landscapes.

The expansion of commercial oil palm crop has modified much of the natural landscape, subsequently leading to biodiversity loss in Southeast Asia. Aside from large-scale oil palm monoculture plantations, self-managed oil palm smallholdings are also becoming common in palm oil producing countries, but less is known about how management of the smallholdings affects faunal biodiversity. We argue that it is critically important to understand the role of habitat complexity at the local and landscape scales for maintaining faunal biodiversity in oil palm smallholdings. We used passive sampling methods to survey understory birds, fruit bats, and butterflies in oil palm smallholdings on the west coast of Peninsular Malaysia. We quantified the diversity in each taxon and measured in situ habitat quality and landscape metrics. We found that oil palm smallholdings located near rice fields supported fewer bird species. Proximity to roads can give rise to bird and fruit bat richness. Bird and fruit bat richness declined at sites with high crop density. Fruit bat richness declined, but butterfly richness increased, with the height of oil palm stands. Butterfly richness declined with distance from riparian habitats. Decreased coverage and height of ground vegetation also negatively affected butterfly species richness. We also found that the number of farm houses is positively related to bird, fruit bat, and butterfly species richness. Of the three taxa, only butterfly richness was positively influenced by crop diversity. We found that habitat complexity enables smallholdings to support a diverse community of birds and butterflies, but not fruit bats. These findings imply that oil palm smallholdings can be managed in a conservation agricultural matrix, as the smallholdings were able to maintain farmland biodiversity.

1 In many developing countries, commercial oil palm farming supports the livelihood of millions of small-scale farmers in the rural areas. However, forest conversion into oil palm monocultures has a major impact on tropical biodiversity. In existing oil palm production landscapes, little is known about how different oil palm agricultural practices affect farmland biodiversity, particularly insect biota. 2 We quantified fruit-feeding butterfly species richness and community composition in oil palm areas subject to polyculture and monoculture farming in Peninsular Malaysia.Polyculture smallholdings were predicted to support greater butterfly diversity than monoculture smallholdings because of the greater structural complexity and floristic diversity associated with crop diversity in polyculture smallholdings. 3 We also identified local-scale habitat attributes important for maintaining fruit-feeding butterfly species richness. 4 We found no significant differences in butterfly species richness, abundance and the composition of butterfly assemblages between polyculture and monoculture smallholdings. Local-scale habitat quality explained 32.1% of the variation in fruit-feeding butterfly richness in oil palm smallholdings. 5 We found that polyculture farming failed to increase fruit-feeding butterfly diversity as a result of a limited number of crop species in oil palm smallholdings. To improve current agricultural practices and maintain high levels of butterfly diversity, commercial growers should increase the number of crop species planted in oil palm smallholdings.