Impacts of oil palm expansion on avian biodiversity in a Neotropical natural savanna

Abstract

The consequences of converting tropical rainforest to oil palm are well-documented, but the impacts of oil palm conversion on natural savanna landscapes remain little-known. Natural savannas in South America have been identified as fertile grounds for future oil palm expansion, partly due to perceived low biodiversity impacts relative to forest systems. We quantify the impacts of oil palm conversion for bird communities inhabiting natural savannas in the Colombian Llanos. Bird species richness and abundance were significantly reduced at sampling points in oil palm relative to adjacent natural savannas, with marked concomitant shifts in community composition. Aquatic, forest and grassland specialists all showed significantly lower abundances in oil palm habitat relative to savanna, as did migratory species and carnivorous/insectivorous dietary guilds. In both habitats, point-level species richness and total bird abundance increased with proximity to remnant forest patches. Within savanna, total bird abundance also decreased with proximity to adjacent oil palm, though species richness was not significantly affected. Within oil palm, point-level abundance increased with proximity to savanna, suggesting that communities in both habitats may be impacted by reciprocal edge or spill-over effects. Point-level abundance in oil palm also increased significantly with the presence of an invasive vine ‘kudzu’, a species introduced in some plantations as a soil protection measure, although species richness was not affected. Our work underlines the need for careful monitoring of further large-scale agro-industrial conversion in the Llanos. In particular, we suggest greater efforts to direct oil palm expansion towards already degraded lands (e.g. improved grassland areas currently used for intensive cattle grazing) to ensure remaining natural savannas are spared

Terrestrial mammal responses to oil palm dominated landscapes in Colombia

“…We hypothesize then, that oil palm can promote the presence of potential prey, such as lizards, frogs, small rodents, snakes, birds, and arthropods, which has been reported in oil palm ecosystems (e.g. [ 83 ][ 84 ][ 96 ][ 97 ][ 98 ]). In this way, these mesopredators could be acting as biological control agents for potential pest species [ 82 ] and thus potentially assisting plantation management.…”

Oil palm monoculture induces drastic erosion of an Amazonian forest mammal fauna

“…This general pattern is consistent with comparable results on the local avifauna surveyed within the same forest landscape, which showed that oil palm plantations were more impoverished in species composition than cattle pastures, secondary forests and primary forests within the same region[ 23 ]. In another study in natural savannas of the Colombian Llanos, species richness and abundance were severely reduced in areas converted into oil palm, and there were marked difference in species composition between habitats[ 24 ]. In contrast, a study in the Colombian Amazon showed that ants, dung beetles, and birds were more diverse in oil palm plantations than in pasture areas, and that oil palm could support a wide range of forest species[ 20 ].…”

“…Faunal diversity responses to these structural changes depending on both the landscape context of plantations and species ecological plasticity in terms of tolerance to a severely modified habitat[ 19 ][ 20 ][ 21 ]. Ecological studies addressing multiple taxa, including birds[ 20 ][ 21 ][ 22 ][ 23 ][ 24 ], reptiles[ 20 ], non-flying small mammals[ 25 ], bats, primates[ 26 ], butterflies[ 27 ], ants[ 28 ] and aquatic invertebrates[ 29 ], have all shown that oil palm plantations are significantly more depauperate than adjacent primary forests, even if these had been selectively-logged[ 12 ].…”

Land management strategies can increase oil palm plantation use by some terrestrial mammals in Colombia

“…30–33 ). Although, investigations into the potential impacts of oil palm production on Colombian fauna have recently increased 32,34–37 , there is still a paucity of information evaluating mammal species responses to oil palm plantations. This information is important, since the capacity of protected areas to function as a mechanism for biodiversity conservation in the long-term is limited, given the increasing rate of degradation occurring in these areas 38,39 , and the surrounding landscapes 40,41 .…”