Exploring the ecological resilience of smallholder oil palm landscapes

Employing more sustainable farming practices could enhance the ecological resilience of tropical oil palm smallholder farms. Concerns about the environmental impacts of oil palm cultivation has led the Roundtable on Sustainable Palm Oil (RSPO) to develop more sustainable management practices. However, it is unclear whether the uptake of such practices will enhance ecological resilience. My study focuses on oil palm smallholdings in Sabah, Malaysian Borneo. Using questionnaire-led interviews with farmers and ecological surveys of their farms, I examined inter-relationships between farm management practices, oil palm yields and the biodiversity, ecosystem functioning, and ecological resilience of farms. Oil palm yields varied widely across smallholder farms (6.9–37.4 t ha−1 yr−1), but there was little evidence that less intensive management reduced farm yields. I surveyed ground dwelling ants on farms to assess species richness and functional diversity (richness and dispersion), and ant-mediated ecosystem functions (scavenging and leaf-litter decomposition). Ant species richness varied among farms (5-30 species), and there were positive associations between native and non-native species (which accounted for 0-40% of ant species on farms). Thus, native ant species persisting in oil palm habitats are resilient to invasion by non-native species, which maintain generalist ecosystem functions on farms. I used Structural Equation Models to investigate the inter-relationships between local factors (e.g., farm management) and wider landscape factors (e.g., proximity to roads and forest) on native and non-native species richness and functional diversity metrics, to make inferences about the ecological resilience of oil palm farms. Both local and landscape factors were important but native and non-native ant species were influenced by different factors. Compared with non-natives, native species contributed most to functional richness and dispersion, occurred on cooler farms, and were associated with higher oil palm yields. Thus, anthropogenic climate warming may reduce the ecological resilience of oil palm farms via its detrimental effects on native species, which may also impact crop yields. I conclude that more efforts should be made to enhance on-farm biodiversity and to develop management practices that support farmer livelihoods, enhance crop yields, and maintain the ecological resilience of oil palm landscapes.