Cattle-grazing in oil palm plantations sustainably controls understory vegetation

Oil palm agricultural practices need to be substantially changed in order to meet the global demand for more ethical and sustainable farming. Livestock integration is an innovative method to control understory vegetation in oil palm plantations, while reducing the need for chemical herbicides, as well as providing additional food security, ecosystem services, and habitat heterogeneity. Understory vegetation is important for faunal biodiversity in oil palm plantations, however it is often decimated by the over usage of herbicides. To determine how cattle-grazing affected the growth of understory vegetation, we collected data from 45 plantations, in Peninsular Malaysia, including those integrated with cattle and without them. Our results revealed that the plantations integrated with cattle had on average 20% more undergrowth coverage, but no difference in undergrowth height, therefore, maintaining undergrowth at an acceptable height for harvesters to access oil palms. We recommend cattle-grazing as a method for oil palm stakeholders to maintain manageable undergrowth and align with sustainable palm oil certification policy by reducing their use of chemical herbicides. To promote cattle-oil palm integration, specific policies are needed to strengthen financial and technical support

Birds associated with different tree species and structures in oil palm agroforestry landscapes in Malaysia

The expansion of oil palm (Elaeis guineensis) cultivation has been recognised as a major threat to tropical biodiversity. Smallholdings, however, unlike large-scale conventional monoculture oil palm plantations, often practice polyculture which may resemble an agroforestry system. These private holdings provide more heterogeneous vegetation which may support greater a greater diversity of birds. This study compared species richness and abundance of birds detected perching in oil palm (both dead and living trees) and seven other planted crop species within oil palm smallholdings. Using transect line surveys, we recorded a total of 816 birds of 39 species from 20 families. Our results indicate that bird species richness and abundance differed significantly between oil palm and the other planted tree species. Non-oil palm trees cumulatively increased bird species richness and abundance. Although birds overall perched more frequently on living oil palm trees (probably reflecting relative abundance), other species including breadfruit, mango, papaya, banana, and coconut, as well as dead trees, were also used. By measuring effect size, we also found that both bird species richness and abundance rely on tree structure and type of tree species. These findings tentatively suggest that providing a larger diversity of tree species within intensively managed oil palm plantations may support a wider variety of local bird species compared to monocultures

Urban forest fragmentation impoverishes native mammalian biodiversity in the tropics

Urban expansion has caused major deforestation and forest fragmentation in the tropics. The impacts of habitat fragmentation on biodiversity are understudied in urban forest patches, especially in the tropics and little is known on the conservation value of the patches for maintaining mammalian biodiversity. In this study, camera trapping was used to determine the species composition and species richness of medium‐ and large‐sized mammals in three urban forest patches and a contiguous forest in Peninsular Malaysia. We identified the key vegetation attributes that predicted mammal species richness and occurrence of herbivores and omnivores in urban forest patches. A total number of 19 mammal species from 120 sampling points were recorded. Contiguous forest had the highest number of species compared to the urban forest patches. Sunda Pangolin and Asian Tapir were the only conservation priority species recorded in the urban forest patches and contiguous forest, respectively. Top predators such as Malayan Tiger and Melanistic Leopard were completely absent from the forest patches as well as the contiguous forest. This was reflected by the abundance of wild boars. We found that mammal species richness increased with the number of trees with DBH less than 5 cm, trees with DBH more than 50 cm, and dead standing trees. In the future, the remaining mammal species in the urban forest patches are expected to be locally extinct as connecting the urban forest patches may be infeasible due to land scarcity. Hence, to maintain the ecological integrity of urban forest patches, we recommend that stakeholders take intervention measures such as reintroduction of selected species and restocking of wild populations in the urban forest patches to regenerate the forest ecosystems

Alley-cropping system increases vegetation heterogeneity and moderates extreme microclimates in oil palm plantations

Forest conversion to oil palm plantation is causing a major loss of biodiversity in Southeast Asia and other tropical regions. Oil palm plantations have less biodiversity because of their simplified vegetation, human disturbances, and extreme microclimate conditions. Alley-cropping system incorporates a secondary crop in the alleys between the main crops. In some cases alley-cropping can result in a greater vegetation structural complexity, thus potentially providing agricultural and ecological benefits, including: buffering against weather extremes, reduction in soil erosion, increased biodiversity, and increased nutrient and water-use efficiency. In this study, we compared vegetation structure (height and cover of vegetation), microclimate (air temperature, relative humidity, light intensity and wind speed), and soil conditions (soil surface temperature, soil pH and soil moisture) across a range of alley-cropping systems and two ages of monoculture oil palm. We found that alley- cropping system had varied structural complexity across different crops when compared to oil palm monoculture system. Careful selection of crops was essential, with black pepper and cacao having the largest impact on improving vegetation heterogeneity and microclimate regulation when incorporated into an alley-cropping system. In particular, we found that systems intercropped with black pepper had air and soil surface temperatures up to 1.3 °C and 2.1 °C cooler than those in oil palm monoculture. In contrast, systems intercropped with bactris and bamboo had increased air temperatures. Our findings show that some alley-cropping systems have great potential as a climate-smart practice in sustainable oil palm agriculture. This study also shows that careful selection of crops is important in the planning and management of future alley-cropping system to optimise the ecosystem benefits that can be gained from this management system

Higher mortality rates for large‐ and medium‐sized mammals on plantation roads compared to highways in Peninsular Malaysia

The fragmentation of forests by agricultural expansion, urbanization, and road networks is an ongoing global biodiversity crisis. In Southeast Asia and other tropical regions, wildlife populations are being isolated into pockets of natural habitat surrounded by road networks and monoculture plantations. Mortality from wildlife–vehicle collisions (WVCs) is contributing to a decline in many species of conservation priority in human-modified landscapes. This study is the first in Malaysia to investigate factors affecting the occurrence of WVCs. We assessed roadkill data gathered by the Department of Wildlife and National Parks on small-, medium-, and large-sized mammals in Peninsular Malaysia. We examined the relationship between wildlife road accidents and several environmental factors. We found a total of 605 roadkill animals, involving 21 species, which included three species classified as Endangered. Road type (plantation road or highway), year, and distance of the road from continuous and fragmented forests were significant in determining mammal mortality. Unexpectedly, the majority of road mortality occurred on palm oil plantation roads compared to highways. Mortality of small- and medium-sized mammals was greater at locations further from continuous forest than those closer to fragmented forests. Segmentation of continuous forest by roads should be avoided wherever possible to reduce the threat of roads on crossing wildlife

Predation of potential insect pests in oil palm plantations, rubber tree plantations, and fruit orchards

In human‐modified landscapes, important ecological functions such as predation are negatively affected by anthropogenic activities, including the use of pesticides and habitat degradation. Predation of insect pests is an indicator of healthy ecosystem functioning, which provides important ecosystem services, especially for agricultural systems. In this study, we compare predation attempts from arthropods, mammals, and birds on artificial caterpillars in the understory, between three tropical agricultural land‐use types: oil palm plantations, rubber tree plantations, and fruit orchards. We collected a range of local and landscape‐scale data including undergrowth vegetation structure; elevation; proximity to forest; and canopy cover in order to understand how environmental variables can affect predation. In all three land‐use types, our results showed that arthropods and mammals were important predators of artificial caterpillars and there was little predation by birds. We did not find any effect of the environmental variables on predation. There was an interactive effect between land‐use type and predator type. Predation by mammals was considerably higher in fruit orchards and rubber tree than in oil palm plantations, likely due to their ability to support higher abundances of insectivorous mammals. In order to maintain or enhance natural pest control in these common tropical agricultural land‐use types, management practices that benefit insectivorous animals should be introduced, such as the reduction of pesticides, improvement of understory vegetation, and local and landscape heterogeneity

Cattle grazing benefits farmland bird community composition in oil palm plantations

Oil palm expansion has caused considerable biodiversity loss as rainforest has been converted to plantation. However, it is still possible to mitigate such biodiversity losses and increase agricultural sustainability by introducing sustainable oil palm farming practices. One such method is the use of biological control agents for understory weed management in place of herbicides. Integrating cattle into oil palm plantation management to control undergrowth is expected to improve biodiversity (including avian diversity) in oil palm plantations. This study investigated the association between cattle grazing and farmland bird species composition in oil palm plantations. We used point transect sampling to survey farmland birds in 45 oil palm plantations which were divided into systematically and non-systematically cattle grazed plantations and control plantations (without cattle grazing). We found that both oil palm plantations with systematic (P=0.001) and non-systematic (P=0.005) cattle grazing had greater avian diversity than plantations without cattle grazing. Based on feeding guild, avian insectivores made up the majority of farmland birds observed. Bird species composition was determined by four attributes in our model: number of cattle, selective weeding frequency, age of oil palm stand, and palm height. We conclude that systematic grazing can improve avian diversity in oil palm plantations. We stress, that cattle integration into oil palm agriculture can provide an excellent means of maximising agricultural land use efficiency as well as increasing biodiversity in agricultural landscapes by increasing habitat complexity

Alley-cropping system can boost arthropod biodiversity and ecosystem functions in oil palm plantations

Oil palm (Elaeis guineensis) is among the fastest expanding crops, due to high global demand for vegetable oils. Large areas of forest are converted into oil palm plantation to meet the market demand in producing countries which causes rapid decline in tropical biodiversity, including arthropods. The alley-cropping system has the potential to promote faunal biodiversity, related ecosystem services and food security in agricultural landscapes. In alley-cropping, a main crop is intercropped with a secondary crop (often a food crop), secondary crops are cultivated in the alleys in between the main crop. We compared arthropod taxonomic richness, arthropod predators and decomposers between five alley-cropping treatments (pineapple, bamboo, black pepper, cacao, bactris), where oil palm is intercropped with another species. In addition, we sampled two control treatments: monoculture oil palm, aged seven and 15 years old. A total of 50,155 arthropod individuals were recorded using pitfall trap sampling, representing 19 orders and 28 families. Fourteen orders belonging to sub-phylum Insecta, three orders from Arachnida (Araneae; Acarinae; Scorpiones) and two orders from Myriapoda (Chordeumatida; Geophilomorpha). We detected an increase in beta-diversity of oil palm production landscape. Specifically, we found that the number of arthropod orders, families and abundance were significantly greater in alley-cropping farming plots than those in monoculture plots. In addition, alley-cropping treatments contained larger numbers of predators and decomposers. Our findings suggest that the alley-cropping system can become a key management strategy to improve biodiversity and ecosystem functions within oil palm production landscapes

Understory vegetation in oil palm plantations benefits soil biodiversity and decomposition rates

Oil palm is the most productive vegetable oil crop per unit area and is crucial to the economy of developing countries such as Malaysia and Indonesia. However, it is also highly controversial due to the impact it has on biodiversity. Inputs of herbicides to control understory vegetation in plantations are high, which is likely to harm native biodiversity, but may be unnecessary in protecting oil palm yield. In this study we investigate the effects of understory manipulation using herbicides on soil fauna, litter decomposition rates and soil abiotic variables: pH, soil organic carbon, soil water content, nitrogen, carbon/nitrogen ratio, potassium and phosphorous. Understory vegetation was manipulated in three treatments: enhanced understory complexity (no herbicides, developed understory), normal understory complexity (intermediate herbicide use with some manual removal) and reduced understory complexity (heavy herbicide use, no understory vegetation). Two years after treatment, soil macrofauna diversity was higher in the enhanced than the normal and reduced understory treatment. Furthermore, both macrofauna abundance and litter decomposition was higher in the enhanced than the reduced understory treatment. By contrast, soil fertility did not change between treatments, perhaps indicating there is little competition between oil palms and understory vegetation. The reduction of herbicide use should be encouraged in oil palm plantations, this will not only reduce plantation costs, but improve soil biodiversity and ecosystem functioning.We are grateful to Pt Ivo Mas Tunggal and Golden Agri Resources for allowing us to conduct research on their oil palm plantations, as well as The Isaac Newton Trust, Cambridge and Sinar Mas Agro Resources and Technology Corporation Research Institute (SMARTRI) for funding the BEFTA Project and providing the resources necessary to conduct all fieldwork. We are grateful to SMARTRI researchers and staff, particular thanks to the SMARTRI soil chemistry laboratory for their advice and support with all aspects of the field data collection and for assistance with sample preparations, and soil nutrient analysis ... AA-B was funded by the National Environmental Research Council (NERC) [grant number NE/L002531/1], ET and JS were supported by the Natural Environment Research Council [grant number NE/P00458X/1]. KP acknowledges support from the Institute for Life Sciences at Southampton University. AH acknowledges support from the Claire Barnes Studentship from the Department of Zoology, University of Cambridge. We thank RISTEK for research permission to set up and collect data from the BEFTA plots (426/SIP/FRP/SM/XI/2012, 72/EXT/SIP/FRP/SM/IX/2013, 44/EXT/SIP/FRP/SM/IX/2014)

Managing Oil Palm Plantations More Sustainably: Large-Scale Experiments Within the Biodiversity and Ecosystem Function in Tropical Agriculture (BEFTA) Programme

Conversion of tropical forest to agriculture results in reduced habitat heterogeneity, and associated declines in biodiversity and ecosystem functions. Management strategies to increase biodiversity in agricultural landscapes have therefore often focused on increasing habitat complexity; however, the large-scale, long-term ecological experiments that are needed to test the effects of these strategies are rare in tropical systems. Oil palm (Elaeis guineensis Jacq.)—one of the most widespread and important tropical crops—offers substantial potential for developing wildlife-friendly management strategies because of its long rotation cycles and tree-like structure. Although there is awareness of the need to increase sustainability, practical options for how best to manage oil palm plantations, for benefits to both the environment and crop productivity, have received little research attention. In this paper we introduce the Biodiversity and Ecosystem Function in Tropical Agriculture (BEFTA) Programme: a long-term research collaboration between academia and industry in Sumatra, Indonesia. The BEFTA Programme aims to better understand the oil palm agroecosystem and test sustainability strategies. We hypothesise that adjustments to oil palm management could increase structural complexity, stabilise microclimate, and reduce reliance on chemical inputs, thereby helping to improve levels of biodiversity and ecosystem functions. The Programme has established four major components: (1) assessing variability within the plantation under business-as-usual conditions; (2) the BEFTA Understory Vegetation Project, which tests the effects of varying herbicide regimes; (3) the Riparian Ecosystem Restoration in Tropical Agriculture (RERTA) Project, which tests strategies for restoring riparian habitat; and (4) support for additional collaborative projects within the Programme landscape. Across all projects, we are measuring environmental conditions, biodiversity, and ecosystem functions. We also measure oil palm yield and production costs, in order to assess whether suggested sustainability strategies are feasible from an agronomic perspective. Early results show that oil palm plantation habitat is more variable than might be expected from a monoculture crop, and that everyday vegetation management decisions have significant impacts on habitat structure. The BEFTA Programme highlights the value of large-scale collaborative projects for understanding tropical agricultural systems, and offers a highly valuable experimental set-up for improving our understanding of practices to manage oil palm more sustainably