Mitigating the impact of oil-palm monoculture on freshwater fishes in Southeast Asia

Abstract

Anthropogenic land-cover change is driving biodiversity loss worldwide. At the epicenter of this crisis lies Southeast Asia, where biodiversity-rich forests are being converted to oil-palm monocultures. As demand for palm oil increases, there is an urgent need to find strategies that maintain biodiversity in plantations. Previous studies found that retaining forest patches within plantations benefited some terrestrial taxa but not others. However, no study has focused on aquatic taxa such as fishes, despite their importance to human well-being. We assessed the efficacy of forested riparian reserves in conserving freshwater fish biodiversity in oil-palm monoculture by sampling stream fish communities in an oil-palm plantation in Central Kalimantan, Indonesia. Forested riparian reserves maintained preconversion local fish species richness and functional diversity. In contrast, local and total species richness, biomass, and functional diversity declined markedly in streams without riparian reserves. Mechanistically, riparian reserves appeared to increase local species richness by increasing leaf litter cover and maintaining coarse substrate. The loss of fishes specializing in leaf litter and coarse substrate decreased functional diversity and altered community composition in oil-palm plantation streams that lacked riparian reserves. Thus, a land-sharing strategy that incorporates the retention of forested riparian reserves may maintain the ecological integrity of fish communities in oil-palm plantations. We urge policy makers and growers to make retention of riparian reserves in oil-palm plantations standard practice, and we encourage palm-oil purchasers to source only palm oil from plantations that employ this practice.

Revealing the pathways by which agricultural land‐use affects stream fish communities in South Brazilian grasslands

“…Whereas our findings are consistent with previous studies demonstrating the effects of agricultural activities measured at multiple spatial scales on instream habitat and fish communities (e.g. Wang et al ., ; Iwata, Nakano & Inoue, ; Lorion & Kennedy, ; Giam et al ., ), we provide additional evidence on the different pathways by which agricultural activities at each scale likely affect fish communities. Our results suggest the mechanisms affecting aquatic communities may depend on the spatial scale used to evaluate human impacts.…”

Bottom‐up influences on tropical freshwater food web structure support the “environmental filtering” hypothesis

“…Here, lower DIC scores suggest greater parsimony. Further, we evaluated model fit using adjusted R 2 ( ) obtained via comparisons between model predictions and observed data (after Giam et al ). Pairwise data can sometimes result in the inflation of the likelihood of Type 1 errors (i.e., incorrect rejection of a true null hypothesis).…”

How Should Beta-Diversity Inform Biodiversity Conservation?

“…Using beta-diversity for conservation: metrics, opportunities, and pitfalls Diversity loss and spatial scaling Conservation planning requires detailed biodiversity data to inform actions 80 ranging from land purchases and management [31][32][33] to agricultural policy and international carbon payments [34][35][36]. However, our understanding of the magnitude of biodiversity loss (or gain) depends on the scale at which we measure it [37].…”