Limited evidence of biodiversity spillover from forest fragments into oil palm plantations in the Amazon

Oil palm expansion is a major driver of the biodiversity extinction crisis. Emerging frontiers of oil palm development in the Amazon risk major biodiversity loss. Spillover of biodiversity from adjacent forest fragments into plantations may reduce the loss of functional and phylogenetic diversity, but the extent of this effect remains unclear.

We surveyed bird communities in large forest fragments and oil palm plantations in the Brazilian Amazon during the dry seasons of 2012 and 2016. We assessed the loss of avian functional and phylogenetic diversity due to forest conversion, its impact on community structure, and whether the percentage of forest and proximity to fragments in oil palm points mitigate losses.

Compared to forest fragments, oil palm plantations exhibited lower phylogenetic and functional diversity. Conversion had a strong negative effect on functional structure, shifting communities from overdispersed to clustered, while phylogenetic structure remained largely unchanged. Trait composition also differed significantly between habitats, with shifts in the distribution of traits related to foraging behaviour, movement, and flight efficiency.

Surrounding forest cover did not mitigate the loss of functional and phylogenetic diversity in plantations. Although bird communities closer to forest edges showed higher mean nearest taxon distance (MNTD) and its standardized value (sesMNTD), the spillover effect was weak, as indicated by the low R² in our models.

Synthesis and Applications: Converting primary forest into oil palm plantations results in substantial biodiversity losses, highlighting the urgent need to preserve the few remaining large forest fragments in the area. Measures that enhance matrix permeability are essential to conserving the evolutionary and functional integrity of Amazonian landscapes and mitigating the negative effects of oil palm expansion.