Predatory ability of <i>Sycanus annulicornis</i> Dohrn. (Hemiptera: Reduviidae) on nettle caterpillar prey (<i>Setora nitens</i> Walker.) (Lepidoptera: Noctuidae) in the laboratory

In Sumatra, Indonesia, the establishment of oil palm and rubber plantations is widespread. However, it occurs at the expense of forest area. Since global demand for palm oil and rubber is increasing, forest conversion is expected to continue. Furthermore, studies have shown that forest destruction and the establishment of agricultural land uses influence the soil–atmosphere exchange of the climate-relevant trace gases carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and nitric oxide (NO). Nevertheless, trace gas measurements from oil palm and rubber plantations are scarce. Additionally, researchers have so far not considered oil palm canopy soils as a possible source or sink of trace gases. The present thesis consists of three studies, which assess the impact of forest conversion into smallholder oil palm and rubber plantations on soil CO2 and CH4 fluxes, as well as on soil N2O and NO fluxes, and which investigate the importance of oil palm canopy soil for N2O and CH4 fluxes. We conducted the studies on highly weathered tropical soils in Jambi Province, Sumatra, Indonesia and selected two soil landscapes which mainly differ in texture (clay and loam Acrisol). To examine the impact of land-use change on soil trace gas fluxes we investigated four different land uses per landscape: lowland forest and jungle rubber (rubber trees interspersed in secondary forest), as reference land uses, as well as smallholder rubber (7–17 years old) and oil palm plantations (9–16 years old), as converted land uses. Each land use was replicated four times in both landscapes.
\n\tThe first study investigated changes in soil CO2 and CH4 fluxes with forest conversion to smallholder oil palm and rubber plantations. We determined soil CO2 and CH4 fluxes monthly from December 2012 to December 2013, using static vented chambers. Our findings show that soil CO2 fluxes in oil palm plantations were reduced and that fluxes from the other three land uses were comparable among each other in both landscapes. We attributed this decrease to strongly decomposed soil organic matter, reduced soil carbon (C) stocks as well as to phosphorus fertilization and liming, which led to a lower C allocation to roots. Due to reduced nitrogen (N) availability in the converted land uses CH4 uptake was lower in oil palm and rubber when compared to the reference land uses in both landscapes. Thus, soil fertility appeared to be an important controller of soil CO2 and CH4 fluxes in this tropical landscape.
\n\tThe second study focused on the impact of forest conversion into smallholder oil palm and rubber plantations on soil N2O and NO fluxes. Additionally, we compared soil N2O fluxes from smallholder oil palm plantations with fluxes from a large-scale oil palm plantation. We determined soil N2O fluxes monthly from December 2012 to December 2013 in the two landscapes and weekly to bi-weekly from July 2014 to July 2015 in the large-scale oil palm plantation, using static vented chambers. Using open dynamic chambers, we measured soil NO fluxes four times in all land uses of both landscapes between March and September 2013. Our results show that land use change did not affect soil N2O and NO fluxes because of low initial N availability in the reference land uses, so that N2O and NO fluxes were also low, and any changes due to conversion might have been too small to identify. However, the large-scale oil palm plantation, although not significantly different, showed, because of their higher fertilizer input, on average 3.5 times higher soil N2O fluxes than the smallholder oil palm plantations.
\n\tThe aim of the third study was to quantify N2O and CH4 fluxes from oil palm canopy soils. We measured soil N2O and CH4 from three different stem heights in eight smallholder oil palm plantations across the two landscapes from February 2013 to May 2014, on a bi-weekly to monthly basis, using in-situ incubation. Oil palm canopy soil emitted N2O and CH4 from all stem heights. However, fluxes were low compared to ground soil fluxes. This was due to a low amount of canopy soil on a hectare basis and due to high nitrate contents, which might have suppressed CH4 production.
\n\tIn the synthesis of this dissertation, data on soil trace gas fluxes were embedded into a broader context to gain information on changes of the net biome exchange (NBE) and on partial N budgets with land-use change. Soil CO2 and CH4 fluxes were combined with an ancillary study on net primary production and harvest as well as with estimations on the contribution of heterotrophic soil respiration to total soil respiration. Soil N2O and NO fluxes were combined with ancillary studies on N inputs and outputs via fertilization, bulk precipitation, leaching and harvest. The results revealed that the NBE of oil palm plantations was higher compared to forest. Nevertheless, implications for climate change are negative since forest conversion itself results in a huge C loss, which cannot be compensated over time by oil palm plantations. The lowest partial N budget was detected in oil palm, indicating that N inputs via precipitation and fertilization were smaller than the huge N loss via harvest. Overall, these results illustrate that land-use change has negative effects on the C and N budgets of tropical ecosystems.

Abstract. Oil palm (Elaeis guineensis) and rubber (Hevea brasiliensis) plantations cover large areas of former rainforest in Sumatra, Indonesia, supplying the global demand for these crops. Although forest conversion is known to influence soil nitrous oxide (N2O) and nitric oxide (NO) fluxes, measurements from oil palm and rubber plantations are scarce (for N2O) or nonexistent (for NO). Our study aimed to (1) quantify changes in soil–atmosphere fluxes of N oxides with forest conversion to rubber and oil palm plantations and (2) determine their controlling factors. In Jambi, Sumatra, we selected two landscapes that mainly differed in texture but were both on heavily weathered soils: loam and clay Acrisol soils. Within each landscape, we investigated lowland forests, rubber trees interspersed in secondary forest (termed as jungle rubber), both as reference land uses and smallholder rubber and oil palm plantations as converted land uses. In the loam Acrisol landscape, we conducted a follow-on study in a large-scale oil palm plantation (called PTPN VI) for comparison of soil N2O fluxes with smallholder oil palm plantations. Land-use conversion to smallholder plantations had no effect on soil N-oxide fluxes (P = 0. 58 to 0.76) due to the generally low soil N availability in the reference land uses that further decreased with land-use conversion. Soil N2O fluxes from the large-scale oil palm plantation did not differ with those from smallholder plantations (P = 0. 15). Over 1-year measurements, the temporal patterns of soil N-oxide fluxes were influenced by soil mineral N and water contents. Across landscapes, annual soil N2O emissions were controlled by gross nitrification and sand content, which also suggest the influence of soil N and water availability. Soil N2O fluxes (µg N m−2 h−1) were 7 ± 2 to 14 ± 7 (reference land uses), 6 ± 3 to 9 ± 2 (rubber), 12 ± 3 to 12 ± 6 (smallholder oil palm) and 42 ± 24 (large-scale oil palm). Soil NO fluxes (µg N m−2 h−1) were −0.6 ± 0.7 to 5.7 ± 5.8 (reference land uses), −1.2 ± 0.5 to −1.0 ± 0.2 (rubber) and −0.2 ± 1.2 to 0.7 ± 0.7 (smallholder oil palm). To improve the estimate of soil N-oxide fluxes from oil palm plantations in this region, studies should focus on large-scale plantations (which usually have 2 to 4 times higher N fertilization rates than smallholders) with frequent measurements following fertilizer application.

Indonesia lost more tropical forest than all of Brazil in 2012, mainly driven by the rubber, oil palm, and timber industries. Nonetheless, the effects of converting forest to oil palm and rubber plantations on soil organic carbon (SOC) stocks remain unclear. We analyzed SOC losses after lowland rainforest conversion to oil palm, intensive rubber, and extensive rubber plantations in Jambi Province on Sumatra Island. The focus was on two processes: (1) erosion and (2) decomposition of soil organic matter. Carbon contents in the Ah horizon under oil palm and rubber plantations were strongly reduced up to 70% and 62%, respectively. The decrease was lower under extensive rubber plantations (41%). On average, converting forest to plantations led to a loss of 10 Mg C ha(-1) after about 15 years of conversion. The C content in the subsoil was similar under the forest and the plantations. We therefore assumed that a shift to higher δ(13) C values in plantation subsoil corresponds to the losses from the upper soil layer by erosion. Erosion was estimated by comparing the δ(13) C profiles in the soils under forest and under plantations. The estimated erosion was the strongest in oil palm (35 ± 8 cm) and rubber (33 ± 10 cm) plantations. The (13) C enrichment of SOC used as a proxy of its turnover indicates a decrease of SOC decomposition rate in the Ah horizon under oil palm plantations after forest conversion. Nonetheless, based on the lack of C input from litter, we expect further losses of SOC in oil palm plantations, which are a less sustainable land use compared to rubber plantations. We conclude that δ(13) C depth profiles may be a powerful tool to disentangle soil erosion and SOC mineralization after the conversion of natural ecosystems conversion to intensive plantations when soils show gradual increase of δ(13) C values with depth.

Over the last two decades, Sumatra, Indonesia has experienced rapid expansion of rubber and oil palm plantations through conversion of rainforests. This is evident from the 36% decrease in forest area in this region from 1990-2010. Such rapid land-use change necessitates assessment of its environmental impacts. Forest conversion to rubber and oil palm plantations are expected to increase nutrient leaching losses and decrease nutrient retention efficiency, following the changes in soil cover, litter input, soil nutrient availability and management practices. This thesis presents two studies, which focused on the impact of forest conversion to rubber and oil palm plantations on nutrient leaching and nutrient retention efficiency, and on the difference in nutrient leaching losses between fertilized and frond-stacked areas of oil palm plantations. All studies were conducted in two landscapes of highly weathered soils that mainly differed in texture (loam and clay Acrisol soils), located in the Jambi province, Sumatra, Indonesia. Nutrient leaching losses were measured using suction cup lysimeters installed at 1.5 m soil depth and sampling frequency was bi-weekly to monthly during February to December 2013. In the first study, nutrient leaching losses and nutrient retention efficiency in the soil were measured in four land uses: the reference land uses of lowland forest and jungle rubber (rubber trees interspersed in secondary forest), and the converted land uses of smallholder rubber and oil palm plantations. In each landscape, the first three land uses were represented by four replicate sites and the oil palm by three sites, totaling 30 sites. The results illustrated that for the reference land uses the loam Acrisol soil had higher leaching fluxes of dissolved nitrogen (N) and base cations, and lower retention efficiencies of N and base cations than the clay Acrisol soil. For the converted land uses, management practices such as fertilization and liming in oil palm plantations resulted in higher dissolved N, dissolved organic carbon (DOC), and base cations leaching fluxes, and lower N and base cation retention efficiencies in the soil than the reference land uses. On the other hand, in the unfertilized rubber plantations leaching losses of dissolved N, DOC, and base cations were lower than in the oil palm plantations. Overall, the results showed that clay content and management practices controlled nutrient leaching losses and nutrient retention efficiencies in heavily weathered Acrisol soils of these converted landscapes. In the second study, nutrient leaching losses were measured in fertilized and frond-stacked areas of smallholder oil palm plantations in clay and loam Acrisol soils. The results exhibited higher leaching losses (i.e. N, base cations, total aluminum (Al), total manganese (Mn), total sulfur (S), and chloride (Cl)) in the fertilized area than the frond-stacked area due to pulse rates of applications of mineral fertilizers and lime. At the landscape scale, higher soil nutrient stocks and lower nutrient leaching losses in the clay Acrisol soil compared to the loam Acrisol soil both in the fertilized and frond stack areas were caused by the higher nutrient retention as a result of higher clay content. Combining nutrient leaching losses and nutrient input (i.e. bulk precipitation and fertilizers) with ancillary studies on nutrient output through harvest export provides more comprehensive information about the changes in partial nutrient budgets of N, phosphorus (P), and base cations due to forest conversion to oil palm and rubber plantations. Fertilized oil palm plantations had the lowest annual partial budget of N, calcium (Ca) and magnesium (Mg) due to the high annual leaching losses and harvest export. However, the high negative partial budgets of N, Ca and Mg in oil palm plantations did not significantly decrease those stocks at 1-m soil depth compared to all the other land uses, except for exchangeable Mg in the loam Acrisol landscape. Even though unfertilized rubber plantations have lower leaching losses (e.g. P) than forest, harvest export caused the lower annual partial budget of P. Overall, these results from the two studies suggests for improved management practices on these highly weathered soils through synchronizing rate of application of fertilizer with plant uptake and frequency of fertilizer application.

This study assessed changes in soil properties and soil fertility resulting from land‐use conversion from rainforest to oil palm and rubber plantations in Okomu Forest Reserve, Southern Nigeria. We collected 315 soil samples at 0–15, 15–30, and 30–60 cm and analyzed soil physicochemical properties. In addition, soil fertility index (SFI) was computed using the analytical hierarchical process. Our results showed that soil organic carbon declined by 40% and 60% (0–15 cm), 32% and 57% (15–30 cm) and 33% and 57% (30–60 cm) in oil palm and rubber plantations, respectively. Similarly, total nitrogen also declined by 43% and 56% (0–15 cm), 34% and 36% (15–30 cm), and 36% and 41% (30–60 cm) in oil palm and rubber plantations and was significantly lower in plantation soil than in the rainforest soil. Soil organic carbon and total nitrogen were, however, higher under oil palm than rubber plantations. In contrast, available phosphorus was higher under rubber plantations than oil palm plantations. The mean values of soil exchangeable potassium and sodium are significantly lower in the rainforest samples. Generally, SFI ranged from 7.30 to 20.46 in the rainforest, 4.16–13.21 in oil palm and 5.15–8.03 in rubber plantations. We conclude that soil degradation is more severe in oil palm plantations than in the rubber plantations. This implies that in addition to site‐specific management, species‐specific management strategy must also be developed to ensure sustainable utilization of soil resources in deforested rainforests.

Soil degradation in oil palm and rubber plantations under land resource scarcity

The area size of oil palm plantation in Indonesia increases significantly every year. The great expansion of oil palm plantation stimulates the emergence of negative accusation that oil palm plantation development caused deforestation, reduction of biodiversity, and environmental degradation. This research aimed to analyze the impact of oil palm plantation development on species diversity of tropical vegetation. This research was conducted on 5 types of land cover in BPME oil palm plantation (young growth oil palm, medium growth oil palm, and old growth oil palm, bush land, and coconut plantation) by single plot method. Research results show that, the change of bush land to oil palm plantation caused biodiversity loss as many as 7 species (38.89%), biodiversity gain as many as 44 species (244.44%) and 18 species being found both in bush land and oil palm plantation, while 3 species of epiphyte moss were found too. On the other hand, change from coconut plantation to become oil palm plantation caused biodiversity loss as many as 6 species (60%), biodiversity gain as many as 52 species (520%) and 10 species being found both in coconut plantation and oil palm plantation, while 3 species of epiphyte moss were also found.

Over the last 18 years, Indonesia has experienced significant deforestation due to the expansion of oil palm and rubber plantations. Accurate land cover maps are essential for policymakers to track and manage land change to support sustainable forest management and investment decisions. An automatic digital processing (ADP) method is currently used to develop land cover change maps for Indonesia, based on optical imaging (Landsat). Such maps produce only forest and non-forest classes, and often oil palm and rubber plantations are misclassified as native forests. To improve accuracy of these land cover maps, this study developed oil palm and rubber plantation discrimination indices using the integration of Landsat-8 and synthetic aperture radar Sentinel-1 images. Sentinel-1 VH and VV difference (>7.5 dB) and VH backscatter intensity were used to discriminate oil palm plantations. A combination of Landsat-8 NDVI, NDMI with Sentinel-1 VV and VH were used to discriminate rubber plantations. The improved map produced four land cover classes: native forest, oil palm plantation, rubber plantation, and non-forest. High-resolution SPOT 6/7 imagery and ground truth data were used for validation of the new classified maps. The map had an overall accuracy of 92%; producer’s accuracy for all classes was higher than 90%, except for rubber (65%), and user’s accuracy was over 80% for all classes. These results demonstrate that indices developed from a combination of optical and radar images can improve our ability to discriminate between native forest and oil palm and rubber plantations in the tropics. The new mapping method will help to support Indonesia’s national forest monitoring system and inform monitoring of plantation expansion.

The characteristics of tropical peatlands are still able to form a high diversity of plants. Conversion of tropical peatlands affects the composition of plants. The aim of this study was to find out effect of land use changes to the composition and diversity of plants in the Peat Hydrological Unit (PHU) Mendahara - Batanghari River. The research was conducted in three land use categories, namely secondary forest, coffee plantation, and oil palm plantation (subdivided into oil palm plantation 1 and oil palm plantation 2). In each study location, sample lane 20 m x 200 m were made. Overall, we found 77 species of plants. The results showed number of plant species decreased due to changes of land use. There are 51 - 53 species of plants in secondary forest areas (out of a total of 58 species) that are not found in oil palm and coffee plantations areas. Differences in composition were also shown in the low value of community similarity (<50%). In the oil palm and coffee plantation areas, plant communities tend to be dominated by pioneer plants such as Melicope lunu-ankenda, Coffea liberica, Macaranga triloba, and Melastoma malabathricum. Secondary forest was dominated by plants species that characterize peatlands such as Tetramerista glabra, Parastemon urophyllus, Knema percoriacea, Litsea costalis var. nidularis and Madhuca motleyana. Changes in land use also reduce the level of diversity (H 'and R) at various levels of growth. Whereas in the oil palm and coffee plantation areas tend to form uniform stands (indicated through index E which describes the abundance distribution in community and index C which describes the dominance of species). Generally, the distribution pattern of plants is clumped. Uniform distribution was found in K. percoriacea and L. costalis var. nidularis. Keywords: land use changes, peatland characteristics, plant composition, plant diversity

Abstract. Hamzah A, Saputra R, Puspita F, Nasrul B, Irfandri, Depari NS. 2021. Ganoderma diversity from smallholder oil palm plantations in peatlands of Kampar District, Indonesia, based on mycelia morphology and somatic incompatibility. Biodiversitas 22: 16-22. Basal Stem Rot disease is caused by the pathogenic fungus Ganoderma boninense which has caused major economic losses in the palm oil industry. Ganoderma boninense has been reported not only infecting crops in the field, but also attacking at the immature phase of the plant even in the nursery. Studies related to Ganoderma diversity in oil palm plantations in Riau, Indonesia have not been widely reported. Ganoderma genetic diversity is important because its provide information regarding the mechanism of infection and the spatial distribution. The Ganoderma spp. isolates were collected from three blocks of smallholder oil palm plantation in Deli Makmur Village, Kampar District, Riau Province, Indonesia and brought to Plant Disease Laboratory, Faculty of Agriculture, Riau University, Pekanbaru, Indonesia. This experimental research was conducted using six Ganoderma isolates (Gan1, Gan2, Gan3, Gan4, Gan5, and Gan6) on the parameters of colony diameter and growth speed, while for the parameters of the morphological diversity of Ganoderma mycelium and the diversity based on somatic incompatibility assay was carried out descriptively. The results of this study show that oil palm plants in smallholder plantations in Kampar District are infected by two groups of Ganoderma based on morphology characteristics using UPGMA dendrogram, but different among isolates based on genetically using somatic incompatibility assay. For the next confirmation, it is necessary to further identify whether the six isolates are different species using molecular identification.

Peatland is an important natural resource for human life because it can be used as growth of oil palm plantation. The growth of oil palm plantations in peatlands is strongly influenced by peat water management. This study aims to study the relationship of different water levels to the content of leaf Cu and Zn nutrients and the growth of oil palm plants ( Elaeis guineensis Jacq.) in the peatlands. This research has been carried out on peatland areas in oil palm plantations of PT. Jatimjaya Perkasa Sei Bangko, Kubu District, Rokan Hilir Regency, Riau Province. Analysis of soil samples and plants samples has been carried out at the Soil Laboratory, Faculty of Agriculture, Universitas Riau, Pekanbaru. The research was conducted in December 2017 to January 2018. This research was conducted using a survey method, the determination of the location of the study using a purposive sampling method, determination of sampling location is determined by stratified sampling method, where the strata in this study are grouped according to different peat water levels namely water level 60 cm with oil palm plants at the same age which is six years and the piezometer has been installed properly. The parameters that observed in this study were soil pH, availability of Cu and Zn nutrient, total soil-K, content of Cu, Zn and K leaves and growth of oil palm plants which included plant height, midrib length and leaflet. The observed data were analyzed for variance and tested further by DNMRT at the level of 5%, analyzed by regression to see the relationship between water level and parameters. The results showed that peatland with water level of 40 - 60 cm had a soil pH, K-total soil, Cu leaves, Zn leaves, midrib length and the highest oil palm plantations compared to peat land with a groundwater level 60 cm, and has a different length of leaflets. Key words : Cu and Zn nutrient, Oil palm plantation, Peatlands, Water Level.

Merten, J., A. Röll, T. Guillaume, A. Meijide, S. Tarigan, H. Agusta, C. Dislich, C. Dittrich, H. Faust, D. Gunawan, J. Hein, . Hendrayanto, A. Knohl, Y. Kuzyakov, K. Wiegand, and D. Hölscher. 2016. Water scarcity and oil palm expansion: social views and environmental processes. Ecology and Society 21(2):5.http://dx.doi.org/10.5751/ES-08214-210205

The expansion of oil palm plantations through the conversion of lowland rice land to oil palm plantations has become a long debate because it is not in accordance with the vision and mission of Mukomuko Regency regarding food self-sufficiency, but in recent years there has been a change in the function of oil palm plantations to lowland rice. About 370 hectares of oil palm and swamp plantations in the Mukomuko District, Bengkulu, were converted into new rice fields. This is interesting to research because this phenomenon is considered unique when in other areas people flock to change the function of food land to oil palm plantations, on the other hand in Mukomuko District the community has shifted land functions from oil palm plantations to lowland rice, even though so far the oil palm farming business . The location selection was carried out purposively and the respondent determination was carried out by the solvin method, which obtained 181 respondents. Collecting data using a survey method by distributing questionnaires to respondents. For data analysis using qualitative and quantitative methods, to see the social impact is described descriptively, while the economic impact is seen from the side of revenue and income. The results of the study explain the social impact of farmers gathering in the fields more often during planting, fertilizing, spraying pests, and at harvest time. Farmers who were previously very consumptive, especially when the price of palm oil went up and experienced difficulties when the price of fresh fruit bunches fell, are now more prudent in managing finances. The environment around the land is now more beautiful and the water quality is getting better. As well as holding more frequent deliberations regarding policies and counseling on lowland rice farming. The economic impact of lowland rice farming generates an income of Rp. 36.151.207 / Ut / Ha / Th. while oil palm farming is Rp. 28,308,303 / Ut / Ha / Th. It can be concluded that the income obtained from lowland rice farming is greater than the income obtained by oil palm farming even though the time period for obtaining income is different, for lowland rice, revenue is obtained within three times a year, while oil palm farmers can earn income every two 14 days. once, or 24 times a year. It means that in terms of income, it increases after the land conversion is carried out..

Oil palm (OP) plantations account for 1.7 % of global CO2 emissions. Numerous studies have focused primarily on greenhouse gas (GHG) emissions from peatlands, constituting 20% of total OP area in the two largest OP producing countries, Indonesia and Malaysia. Few studies have investigated the potential for reducing GHG emissions in OP plantations. Strategies to reduce emissions and sequester carbon must consider how different practices affect production and the environment. Understanding the spatial distribution of GHG intensity and how the environment affects GHG intensity is therefore key to sustainable oil palm production.GHG intensity was used as a metric to map the potential for sustainable OP plantations. GHG intensity represents the GHG emissions / removals (ton C ha-1) per unit of oil palm yields (ton ha-1). The approach for analysing the change in GHG emissions/ removals, referred to as the IPCC tier 1 method, is based on changes in soil organic carbon due to C and N emissions in drained peatlands and the associated change in aboveground biomass due to land use change. Changes in GHG intensity were investigated spatially for a case study in an industrial OP plantation located in Riau Province, Indonesia, from 2015 to 2019. Linear regression was used to analyse the relationships between GHG intensity and agri-environmental variables including NDVI, NPP, GPP, evapotranspiration, soil moisture in the root zone, soil moisture in deeper layer, C and N emissions from organic soils, and soil organic carbon (SOC).The results show that around 90% of the new oil palm plantations in 2019 were converted from timber plantation, swamp scrubland, and bare land in 2015. Consequently, biomass growth from land use change acted as a carbon sink in this period. However, drained organic soils contributed significantly to GHG emissions. The change in GHG intensity in OP plantation in this study varied spatially from emitting (0.19 to 4.10 Ton C eq Ton-1 yields) to removing the GHG (0.23 to 2.40 Ton C eq Ton-1 yields). Among the environmental variables, NDVI and soil moisture showed the strongest relationship with GHG emissions/ removals (R2 = 0.23,   p value = < 2.2e-16) and yields (R2 = 0.2   p value = < 2.2e-16) in OP plantations.These initial findings are advantageous for spatially identifying potential OP plantations that remove or emit GHG. Understanding the relationship between GHG emissions/removals and yields to environment variables provides insight into monitoring and enhancing OP sustainability, both from production and environmental perspectives. Future work will examine non-linear approaches to better model this relationship.   

Abstract. Oil seed crops, especially oil palm, are among the most rapidly expanding agricultural land uses, and their expansion is known to cause significant environmental damage. Accordingly, these crops often feature in public and policy debates which are hampered or biased by a lack of accurate information on environmental impacts. In particular, the lack of accurate global crop maps remains a concern. Recent advances in deep-learning and remotely sensed data access make it possible to address this gap. We present a map of closed-canopy oil palm (Elaeis guineensis) plantations by typology (industrial versus smallholder plantations) at the global scale and with unprecedented detail (10 m resolution) for the year 2019. The DeepLabv3+ model, a convolutional neural network (CNN) for semantic segmentation, was trained to classify Sentinel-1 and Sentinel-2 images onto an oil palm land cover map. The characteristic backscatter response of closed-canopy oil palm stands in Sentinel-1 and the ability of CNN to learn spatial patterns, such as the harvest road networks, allowed the distinction between industrial and smallholder plantations globally (overall accuracy =98.52±0.20 %), outperforming the accuracy of existing regional oil palm datasets that used conventional machine-learning algorithms. The user's accuracy, reflecting commission error, in industrial and smallholders was 88.22 ± 2.73 % and 76.56 ± 4.53 %, and the producer's accuracy, reflecting omission error, was 75.78 ± 3.55 % and 86.92 ± 5.12 %, respectively. The global oil palm layer reveals that closed-canopy oil palm plantations are found in 49 countries, covering a mapped area of 19.60 Mha; the area estimate was 21.00 ± 0.42 Mha (72.7 % industrial and 27.3 % smallholder plantations). Southeast Asia ranks as the main producing region with an oil palm area estimate of 18.69 ± 0.33 Mha or 89 % of global closed-canopy plantations. Our analysis confirms significant regional variation in the ratio of industrial versus smallholder growers, but it also confirms that, from a typical land development perspective, large areas of legally defined smallholder oil palm resemble industrial-scale plantings. Since our study identified only closed-canopy oil palm stands, our area estimate was lower than the harvested area reported by the Food and Agriculture Organization (FAO), particularly in West Africa, due to the omission of young and sparse oil palm stands, oil palm in nonhomogeneous settings, and semi-wild oil palm plantations. An accurate global map of planted oil palm can help to shape the ongoing debate about the environmental impacts of oil seed crop expansion, especially if other crops can be mapped to the same level of accuracy. As our model can be regularly rerun as new images become available, it can be used to monitor the expansion of the crop in monocultural settings. The global oil palm layer for the second half of 2019 at a spatial resolution of 10 m can be found at https://doi.org/10.5281/zenodo.4473715 (Descals et al., 2021).