Neotropical moth assemblages degrade due to oil palm expansion

Oil palm is one of the most rapidly expanding crops throughout the tropics, yet little is known about its impacts on Neotropical invertebrate biodiversity. Responses of insect assemblages to land conversion may substantially vary among taxa. We assessed geometrid and arctiine moth assemblages in a Costa Rican human dominated landscape, where oil palm plantations are now the second most common land cover. Moths were sampled during 6 months with automatic traps in the interior and margin of old-growth forests, young secondary forests and oil palm plantations in a 30 km² area. Our results show that richness and diversity of both taxa were severely reduced in oil palm compared to all other habitats. Geometrid abundance was highest in forest interiors and lowest in oil palm, while arctiine numbers did not differ between habitats. Dominance was highest in oil palm plantations, where one arctiine species and one geometrid species accounted for over 40% of total abundance in each of their respective taxa. Species composition was distinct in oil palm and forest interior sites, and depicted a gradient of habitat disturbance in ordination space that was strongly related to vegetation diversity and structure. This study demonstrates that oil palm plantations are not a suitable habitat for these moth taxa. Whilst some arctiine species seem adapted to disturbed habitats, geometrids were more dependent on old-growth forests, showing higher bioindicator potential. In the face of accelerated oil palm expansion, conservation strategies should focus on protecting old-growth forest remnants, as well as increasing species diversity and structural complexity of degraded habitats.     

Logged peat swamp forest supports greater macrofungal biodiversity than large‐scale oil palm plantations and smallholdings

Intensive land expansion of commercial oil palm agricultural lands results in reducing the size of peat swamp forests, particularly in Southeast Asia. The effect of this land conversion on macrofungal biodiversity is, however, understudied. We quantified macrofungal biodiversity by identifying mushroom sporocarps throughout four different habitats; logged peat swamp forest, large‐scale oil palm plantation, monoculture, and polyculture smallholdings. We recorded a total of 757 clusters of macrofungi belonging to 127 morphospecies and found that substrates for growing macrofungi were abundant in peat swamp forest; hence, morphospecies richness and macrofungal clusters were significantly greater in logged peat swamp forest than converted oil palm agriculture lands. Environmental factors that influence macrofungi in logged peat swamp forests such as air temperature, humidity, wind speed, soil pH, and soil moisture were different from those in oil palm plantations and smallholdings. We conclude that peat swamp forests are irreplaceable with respect to macrofungal biodiversity. They host much greater macrofungal biodiversity than any of the oil palm agricultural lands. It is imperative that further expansion of oil palm plantation into remaining peat swamp forests should be prohibited in palm oil producing countries. These results imply that macrofungal distribution reflects changes in microclimate between habitats and reduced macrofungal biodiversity may adversely affect decomposition in human‐modified landscapes.     

Oil palm expansion into rain forest greatly reduces ant biodiversity in canopy,epiphytes and leaf-litter

Oil palm cultivation is expanding rapidly into many of the world's most biodiverse tropical regions. One of the most functionally important and ecologically dominant animal groups in these environments is the ants. Here, we quantify the overall impacts of clear-felling lowland dipterocarp rainforest and conversion into oil palm plantation on ant diversity. At study sites in Sabah, Malaysia we collected ants from three microhabitats: 1 – the canopy, 2 – bird's nest ferns (Asplenium nidus complex, a common epiphyte in forest and oil palm), and 3 – leaf litter. We also measured temperature, humidity and light at collection sites to assess their impacts on ant community composition. Total ant species richness decreased from 309 to 110 (?64%) between forest and oil palm plantation. However, this impact was not the same across all microhabitats, with bird's nest ferns maintaining almost the same number of ant species in oil palm compared to forest (forest-oil palm, ferns: 36–35 (3% loss), canopy: 120–58 (52% loss), leaf litter: 216–56 (74% loss)). Relative abundance distributions remained the same for fern-dwelling ants, but became less even for oil palm ants in both the canopy and the leaf litter. These differences may be due in part to the ability of bird's nest ferns to provide a stable microclimate in hot, dry plantations. We also found that non-native ant species were more abundant in oil palm than in forest, and few forest ant species survived in plantations in any of the microhabitats. Only 59 of the 309 forest species persisted in oil palm plantations, corresponding to an 81% loss of forest species resulting from habitat conversion. Although oil palm supports many more ant species than has been previously reported, converting forest into plantation still leads to a dramatic reduction in species richness. The maintenance of forested areas is therefore vital for the conservation of ant biodiversity.     

Poor Prospects for Avian Biodiversity in Amazonian Oil Palm

Expansion of oil palm plantations across the humid tropics has precipitated massive loss of tropical forest habitats and their associated speciose biotas. Oil palm plantation monocultures have been identified as an emerging threat to Amazonian biodiversity, but there are no quantitative studies exploring the impact of these plantations on the biome’s biota. Understanding these impacts is extremely important given the rapid projected expansion of oil palm cultivation in the basin. Here we investigate the biodiversity value of oil palm plantations in comparison with other dominant regional land-uses in Eastern Amazonia. We carried out bird surveys in oil palm plantations of varying ages, primary and secondary forests, and cattle pastures. We found that oil palm plantations retained impoverished avian communities with a similar species composition to pastures and agrarian land-uses and did not offer habitat for most forest-associated species, including restricted range species and species of conservation concern. On the other hand, the forests that the oil palm companies are legally obliged to protect hosted a relatively species-rich community including several globally-threatened bird species. We consider oil palm to be no less detrimental to regional biodiversity than other agricultural land-uses and that political pressure exerted by large landowners to allow oil palm to count as a substitute for native forest vegetation in private landholdings with forest restoration deficits would have dire consequences for regional biodiversity.     

Migratory bird community structure in oil palm (Elaies guineensis) plantations and native forest fragments in southern Mexico

Oil palm (Elaies guineensis) plantations are among the fastest growing agroecosystems in the Neotropics, but little is known about how Neotropical birds use oil palm habitats. To better understand the potential value of oil palm as an overwintering habitat for migratory birds, we surveyed birds in oil palm and native forest remnants in Tabasco, Mexico, from 19 December 2017 to 27 March 2018. We collected data on bird abundance and vegetative structure and used generalized linear models and multivariate analysis to assess how oil palm development influenced migrant bird diversity, community assemblages, and abundance. We found that species richness of migratory birds tended to be higher in forest patches than in oil palm, that community assemblages of migratory birds differed between native forest and oil palm plantations, and that differences in migratory bird abundance, and subsequent changes in community assemblages were driven by differences between native forest and oil palm plantations in vegetative structure. The bird community of native forest was characterized by migrant species sensitive to forest loss that forage low in the understory and in the leaf litter, whereas the bird community of oil palm plantations was represented by generalist species that occupy a wider range of foraging niches. Our results suggest that most species of migrant birds responded positively to several forest structural features and that integrating more native trees and increasing the amount of understory vegetation in oil palm plantations may increase the value of working landscapes for migratory birds.     

Local and landscape drivers of arthropod diversity and decomposition processes in oil palm leaf axils

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Effects of Logging and Oil Palm Expansion on Stream Frog Communities on Borneo,Southeast Asia

The conversion of tropical rain forests to oil palm plantations is a major threat to Southeast Asia's rich biodiversity. Fostering forest species communities in secondary forests, agroforestry systems, and plantations is therefore increasingly becoming a conservation focus. This study uses standardized transect‐based sampling to compare species richness, density and community composition of stream anuran assemblages among primary forests, repeatedly logged forests and oil palm plantations in northern Borneo. In primary forest streams, we recorded an average of 19 frog species, compared to 15 species in logged forests and 11 species in oil palm plantation streams. However, the high percentage of canopy cover above the plantation streams mitigated this loss to some extent. This study corroborates numerous studies that oil palm plantations have mainly negative effects on the region's biodiversity. However, our results also demonstrate the high conservation value of logged forests for Bornean stream‐dependent anurans. We conclude that palm plantations have a largely unused potential to promote regional anuran biodiversity.     

Minimizing the biodiversity impact of Neotropical oil palm development

Oil palm agriculture is rapidly expanding in the Neotropics, at the expense of a range of natural and seminatural habitats. A key question is how this expansion should be managed to reduce negative impacts on biodiversity. Focusing on the Llanos of Colombia, a mixed grassland–forest system identified as a priority zone for future oil palm development, we survey communities of ants, dung beetles, birds and herpetofauna occurring in oil palm plantations and the other principal form of agriculture in the region – improved cattle pasture – together with those of surrounding natural forests. We show that oil palm plantations have similar or higher species richness across all four taxonomic groups than improved pasture. For dung beetles, species richness in oil palm was equal to that of forest, whereas the other three taxa had highest species richness in forests. Hierarchical modelling of species occupancy probabilities indicated that oil palm plantations supported a higher proportion of species characteristic of forests than did cattle pastures. Across the bird community, occupancy probabilities within oil palm were positively influenced by increasing forest cover in a surrounding 250 m radius, whereas surrounding forest cover did not strongly influence the occurrence of other taxonomic groups in oil palm. Overall, our results suggest that the conversion of existing improved pastures to oil palm has limited negative impacts on biodiversity. As such, existing cattle pastures of the Colombian Llanos could offer a key opportunity to meet governmental targets for oil palm development without incurring significant biodiversity costs. Our results also highlight the value of preserving remnant forests within these agricultural landscapes, protecting high biodiversity and exporting avian ‘spill‐over’ effects into oil palm plantations.     

Degraded lands worth protecting: the biological importance of Southeast Asia's repeatedly logged forests

Southeast Asia is a hotspot of imperilled biodiversity, owing to extensive logging and forest conversion to oil palm agriculture. The degraded forests that remain after multiple rounds of intensive logging are often assumed to be of little conservation value; consequently, there has been no concerted effort to prevent them from being converted to oil palm. However, no study has quantified the biodiversity of repeatedly logged forests. We compare the species richness and composition of birds and dung beetles within unlogged (primary), once-logged and twice-logged forests in Sabah, Borneo. Logging had little effect on the overall richness of birds. Dung beetle richness declined following once-logging but did not decline further after twice-logging. The species composition of bird and dung beetle communities was altered, particularly after the second logging rotation, but globally imperilled bird species (IUCN Red List) did not decline further after twice-logging. Remarkably, over 75 per cent of bird and dung beetle species found in unlogged forest persisted within twice-logged forest. Although twice-logged forests have less biological value than primary and once-logged forests, they clearly provide important habitat for numerous bird and dung beetle species. Preventing these degraded forests from being converted to oil palm should be a priority of policy-makers and conservationists.     

Replanting of first‐cycle oil palm results in a second wave of biodiversity loss

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Biodiversity of leaf-litter ants in fragmented tropical rainforests of Borneo: the value of publically and privately managed forest fragments

In view of the rapid rate of expansion of agriculture in tropical regions, attention has focused on the potential for privately-managed rainforest patches within agricultural land to contribute to biodiversity conservation. However, these sites generally differ in their history of forest disturbance and management compared with other forest fragments, and more information is required on the biodiversity value of these privately-managed sites, particularly in oil-palm dominated landscapes of SE Asia. Here we address this issue, using tropical leaf-litter ants in rainforest fragments surrounded by mature oil palm plantations in Sabah, Borneo as a model system. We compare the species richness and composition of ant assemblages in privately-managed forest fragments (‘high conservation value’ fragments; HCVs) with those in publically-managed fragments of forest (virgin jungle reserves; VJRs) and control sites in extensive tracts of primary forest. In this way, we test the hypothesis that privately-managed and publically-managed forest fragments differ in their species richness and composition as a result of differences in history and management and hence in habitat quality. In support of this hypothesis, we found that HCVs had much poorer habitat quality than VJRs, including lower sizes and densities of trees, less canopy cover, fewer dipterocarp trees and shallower leaf litter. Consequently, HCVs supported only half the species richness of ants in VJRs, which in turn supported 70 % of the species richness of control sites, with vegetation structure and composition explaining 77 % of the variation among forest fragments in ant species richness. HCVs were also much smaller than VJRs but there was only a weak relationship between fragment size and habitat quality, and species richness was not related to fragment size. VJRs supported 78 % of the 156 species found in extensive tracts of forest whereas HCVs supported only 22 %, which was only slightly higher than the proportion previously recorded in oil palm (19 %). These data support previous findings that publically-managed VJR fragments can make an important contribution to biodiversity conservation within agricultural landscapes. However, we suggest that for these HCVs to be effective as reservoirs of biodiversity, management is required to restore vegetation structure and habitat quality, for instance through enrichment planting with native tree species.     

Do riparian reserves support dung beetle biodiversity and ecosystem services in oil palm-dominated tropical landscapes?

Agricultural expansion and intensification are major threats to global biodiversity, ecological functions, and ecosystem services. The rapid expansion of oil palm in forested tropical landscapes is of particular concern given their high biodiversity. Identifying management approaches that maintain native species and associated ecological processes within oil palm plantations is therefore a priority. Riparian reserves are strips of forest retained alongside rivers in cultivated areas, primarily for their positive hydrological impact. However, they can also support a range of forest‐dependent species or ecosystem services. We surveyed communities of dung beetles and measured dung removal activity in an oil palm‐dominated landscape in Sabah, Malaysian Borneo. The species richness, diversity, and functional group richness of dung beetles in riparian reserves were significantly higher than in oil palm, but lower than in adjacent logged forests. The community composition of the riparian reserves was more similar to logged forest than oil palm. Despite the pronounced differences in biodiversity, we did not find significant differences in dung removal rates among land uses. We also found no evidence that riparian reserves enhance dung removal rates within surrounding oil palm. These results contrast previous studies showing positive relationships between dung beetle species richness and dung removal in tropical forests. We found weak but significant positive relationships between riparian reserve width and dung beetle diversity, and between reserve vegetation complexity and dung beetle abundance, suggesting that these features may increase the conservation value of riparian reserves. Synthesis and applications: The similarity between riparian reserves and logged forest demonstrates that retaining riparian reserves increases biodiversity within oil palm landscapes. However, the lack of correlation between dung beetle community characteristics and dung removal highlights the need for further research into spatial variation in biodiversity–ecosystem function relationships and how the results of such studies are affected by methodological choices.     

Survival strategies of a frugivore,the sun bear,in a forest-oil palm landscape

As large areas of forest are lost throughout the tropics, prime habitat of many species decline and become fragmented. The island of Borneo is a prime example, with accelerated clearing of forests primarily for oil palm expansion. Borneo is recognized as an important stronghold for the conservation of the sun bear (Helarctos malayanus), but it is unclear how habitat reduction and fragmentation is affecting this frugivore. We used camera traps and sign surveys to understand patterns of sun bear habitat use in a matrix of fragmented forests and extensive oil palm development, which has existed as such for?>?15 years: the Lower Kinabatangan floodplain in Sabah, Malaysian Borneo. Within these small forest fragments, squeezed between a major river and oil palm plantations, bears exhibited selection for areas farther from human activity (plantations, river boat traffic, and buildings), and were rarely active during the day, demonstrating both spatial and temporal avoidance of potential human-related threats. They selected large trees to feed and rest, and also exploited adjacent plantations to feed on oil palm fruits. We conclude that even relatively small forest fragments (~?2000 ha) within large agricultural landscapes can be important for sun bears. Our research highlights the remarkable adaptations this species has employed to persist in a drastically modified landscape.     

Land-use effects on local biodiversity in tropical forests vary between continents

Land-use change is one of the greatest threats to biodiversity, especially in the tropics where secondary and plantation forests are expanding while primary forest is declining. Understanding how well these disturbed habitats maintain biodiversity is therefore important—specifically how the maturity of secondary forest and the management intensity of plantation forest affect levels of biodiversity. Previous studies have shown that the biotas of different continents respond differently to land use. Any continental differences in the response could be due to differences in land-use intensity and maturity of secondary vegetation or to differences among species in their sensitivity to disturbances. We tested these hypotheses using an extensive dataset collated from published biodiversity comparisons within four tropical regions—Asia, Africa, Central America and South America—and a wide range of animal and plant taxa. We analysed responses to land use of several aspects of biodiversity—species richness, species composition and endemicity—allowing a more detailed comparison than in previous syntheses. Within each continent, assemblages from secondary vegetation of all successional stages retained species richness comparable to those in primary vegetation, but community composition was distinct, especially in younger secondary vegetation. Plantation forests, particularly the most intensively managed, supported a smaller—and very distinct—set of species from sites in primary vegetation. Responses to land use did vary significantly among continents, with the biggest difference in richness between plantation and primary forests in Asia. Responses of individual taxonomic groups did not differ strongly among continents, giving little indication that species were inherently more sensitive in Asia than elsewhere. We show that oil palm plantations support particularly low species richness, indicating that continental differences in the response of biodiversity to land use are perhaps more likely explained by Asia’s high prevalence of oil palm plantations.     

How will oil palm expansion affect biodiversity?

Oil palm is one of the world's most rapidly increasing crops. We assess its contribution to tropical deforestation and review its biodiversity value. Oil palm has replaced large areas of forest in Southeast Asia, but land-cover change statistics alone do not allow an assessment of where it has driven forest clearance and where it has simply followed it. Oil palm plantations support much fewer species than do forests and often also fewer than other tree crops. Further negative impacts include habitat fragmentation and pollution, including greenhouse gas emissions. With rising demand for vegetable oils and biofuels, and strong overlap between areas suitable for oil palm and those of most importance for biodiversity, substantial biodiversity losses will only be averted if future oil palm expansion is managed to avoid deforestation.     

Impact of Logging and Forest Conversion to Oil Palm Plantations on Soil Bacterial Communities in Borneo

Tropical forests are being rapidly altered by logging and cleared for agriculture. Understanding the effects of these land use changes on soil bacteria, which constitute a large proportion of total biodiversity and perform important ecosystem functions, is a major conservation frontier. Here we studied the effects of logging history and forest conversion to oil palm plantations in Sabah, Borneo, on the soil bacterial community. We used paired-end Illumina sequencing of the 16S rRNA gene, V3 region, to compare the bacterial communities in primary, once-logged, and twice-logged forest and land converted to oil palm plantations. Bacteria were grouped into operational taxonomic units (OTUs) at the 97% similarity level, and OTU richness and local-scale α-diversity showed no difference between the various forest types and oil palm plantations. Focusing on the turnover of bacteria across space, true β-diversity was higher in oil palm plantation soil than in forest soil, whereas community dissimilarity-based metrics of β-diversity were only marginally different between habitats, suggesting that at large scales, oil palm plantation soil could have higher overall γ-diversity than forest soil, driven by a slightly more heterogeneous community across space. Clearance of primary and logged forest for oil palm plantations did, however, significantly impact the composition of soil bacterial communities, reflecting in part the loss of some forest bacteria, whereas primary and logged forests did not differ in composition. Overall, our results suggest that the soil bacteria of tropical forest are to some extent resilient or resistant to logging but that the impacts of forest conversion to oil palm plantations are more severe.     

Tree community structure, dynamics, and diversity partitioning in a Bornean tropical forested landscape

Human-modified forested landscapes are prevalent in the tropics, and the role of complex mosaics of diverse vegetation types in biodiversity conservation remains poorly understood. Demographic traits and the spatial pattern of biodiversity are essential information when considering proper forest management and land use strategies. We compared the tree community structure (stem density, basal area, tree diversity, abundance of rare, endemic, and upper-layer trees, and species composition) and the forest dynamics (mortality, recruitment rate, and increments of basal area, and above- and below-ground biomass) of 39–46 plots among five dominant forest types: young and old fallows, rubber plantations, and fragmented and old-growth forests in Sarawak, Malaysia. We also explored how tree diversity was distributed across different spatial scales using additive partitioning of diversity. Swidden cultivation and rubber plantations showed decreased stem density, basal area, tree diversity, abundance of rare, endemic, and upper-layer trees, and increments of above- and below-ground biomass, which affected tree mortality, dominant trees, and species composition. Little distinction in species composition was observed among young and old fallows and rubber plantations, indicating a relatively quick recovery of the tree community in the early stages. The highest diversity was found among forest types, indicating that the whole forested landscape comprises a suitable scale for tree biodiversity conservation in the region. Our results suggest that although fragmented and old-growth forests have an irreplaceable role and a high priority in conserving biodiversity and sustaining the function of the forest ecosystem, secondary forests may also have a reinforcing role in maintaining tree diversity in the region, especially under the current circumstances in which a large portion of the landscape is human-modified and faces an increasing threat from the expansion of oil palm plantations.     

Diversity and occupancy of small carnivores within oil palm plantations in central Sumatra,Indonesia

In Southeast Asia, the conversion of native forests to oil palm plantations threatens tropical biodiversity, but very little is known about the impacts of oil palm cultivation on small carnivore species. To determine the diversity and occupancy of small carnivores within oil palm plantations and to investigate possible factors that might affect their presence within oil palm, we used camera-traps within two oil palm plantations in central Sumatra, analysed the data using occupancy modelling and tested whether two covariates (distance to the edge of the oil palm habitat and distance from extensive areas of lowland forest) affected the model parameters for each small carnivore species. From 3164 camera-trap days, we detected only three small carnivores: leopard cat (Prionailurus bengalensis), common palm civet (Paradoxurus hermaphroditus) and Malay civet (Viverra tangalunga), which indicates that there was a low diversity of small carnivores within the oil palm plantations. Both the leopard cat and common palm civet were found deep within the oil palm, whereas the Malay civet was only detected near the edge in one of the plantations. The leopard cat and common palm civet had very high occupancy values, whereas the Malay civet had low values for both occupancy and detection probability. Neither covariate affected occupancy of the leopard cat and common palm civet, but distance from the edge of the oil palm habitat did influence their detection probabilities. Malay civet occupancy decreased with distance from the oil palm edge, and detection probability was affected by distance from extensive areas of lowland forest. Forests and rest/den site availability are suggested to be important features for small carnivores with oil palm-dominated landscapes.     

Ant mosaics occur in SE Asian oil palm plantation but not rain forest and are influenced by the presence of nest‐sites and non‐native species

Interaction networks within biotic communities can be dramatically altered by anthropogenic habitat modification. Ants, an important ecological group, often interact competitively to form mosaic‐like patterns in disturbed plantation habitats, in which dominant species form mutually exclusive territories. However, the existence of these ant mosaics in pristine forests is contentious. Here we assess the relative strengths of ant competitive interactions in oil palm plantation and primary rain forest in Sabah, Malaysia, using null models of species co‐occurrence. We use two metrics: the C‐score, which measures mean degree of overall co‐occurrence, and a novel metric, the C_var‐score, which measures the variance in degree of co‐occurrence. We also investigate the role of nest sites by collecting ants from canopy and leaf litter microhabitats, and from epiphytic ferns, an important nest site for canopy ants. Furthermore, we assess whether non‐native species, which were widespread in oil palm plantation (61 occurrences vs five in rain forest) are important in driving the formation of ant mosaics. We found no evidence for ant mosaics in any primary forest microhabitat. In oil palm plantation, segregation between species was pronounced in epiphytes, weak in the rest of the canopy and absent in leaf litter communities. Intriguingly, exclusion of non‐native ant species from analyses increased the degree of negative species co‐occurrence in all three microhabitats, with species segregation in the oil palm canopy becoming statistically significant. Our results suggest that invasion of plantation habitats by non‐native species does not drive increased species segregation in ant communities. Rather, high degrees of species segregation might relate to changes in the importance of canopy nest sites, with colonies competing more strongly for these in plantations. In primary forests, weaker nest‐site limitation and the highly complex, more vertically stratified, non‐uniform canopy could lead to random co‐occurrence between ant species at the scales studied here.     

Establishing the evidence base for maintaining biodiversity and ecosystem function in the oil palm landscapes of South East Asia

The conversion of natural forest to oil palm plantation is a major current threat to the conservation of biodiversity in South East Asia. Most animal taxa decrease in both species richness and abundance on conversion of forest to oil palm, and there is usually a severe loss of forest species. The extent of loss varies significantly across both different taxa and different microhabitats within the oil palm habitat. The principal driver of this loss in diversity is probably the biological and physical simplification of the habitat, but there is little direct evidence for this. The conservation of forest species requires the preservation of large reserves of intact forest, but we must not lose sight of the importance of conserving biodiversity and ecosystem processes within the oil palm habitat itself. We urgently need to carry out research that will establish whether maintaining diversity supports economically and ecologically important processes. There is some evidence that both landscape and local complexity can have positive impacts on biodiversity in the oil palm habitat. By intelligent manipulation of habitat complexity, it could be possible to enhance not only the number of species that can live in oil palm plantations but also their contribution to the healthy functioning of this exceptionally important and widespread landscape.