Palm oil production in Southeast Asia often occurs on nutrient-poor, acidic soils converted from primary forest. Both the agricultural conversion and the production of oil palm are subsidised in Indonesia. As well as depleting soil organic C and plant nutrients, agricultural production on these soils can result in the accumulation of trace elements (TEs)—including micronutrients and non-essential trace elements—from the use of TE-containing agrichemicals including phosphate fertilisers and Cu fungicides. We tested the hypothesis that palm soils will have lower C concentrations than forest soils, as well as accumulation of TEs including Cu, Zn and Cd. Soil samples from active and abandoned oil palm plantations in Sumatra, Indonesia, were analysed for general soil properties as well as TE concentrations. Soils were acidic and low in key nutrients, with production likely to be limited by deficiencies of N, P, K, Mg and Mo, present at some sites in mean concentrations as low as 0.021%, 118 mg kg−1, 778 mg kg−1, 1023 mg kg−1 and 0.095 mg kg−1, respectively. Mean organic C was lower (2.0–3.3%) than reported values in nearby forest soils (7.7%). Soils under palm production contained elevated levels of Cu, Zn, As and Pb up to 38, 91, 9.0 and 28 mg kg−1, respectively, likely due to agrichemical use. The correction of nutrient deficiencies in palm production would require significant fertiliser inputs, which would exacerbate TE accumulation and reduce the net economic revenue from oil production. Our data have shown that in the plantations we have sampled, soils have become degraded. These tropical, weathered, and naturally nutrient-poor soils are ill suited to intensive production that requires high ongoing nutrient inputs. These findings have implications for the sustainability of a regionally significant production system across Southeast Asia.

Punggualas lies in the western part of Sebangau National Park (SNP). It is a logged-over forest, yet it is one of the major strongholds for the P. p. wurmbii population in the SNP. The range size, as well as the ranging pattern for Punggualas, has never been conducted. The study aimed to estimate orangutan ranging size and pattern as well as their distribution over the Punggualas forest. Ranging data within the area of interest (AOI) was collected from Feb 2015 – Dec 2019 (P1), and Mar 2020 – May 2022 (P2). Minimum convex polygon (MCP), range size of orangutan individual was calculated using adehabitatHR package in RStudio 4.1.1 for Windows. We visualized the distribution in ArcGIS 10.5 with Kernel Density (KD) tool. The range size of Mother-Infant is the greatest (259,6 Ha) among all individuals being studied within the study periods. Moreover, the size estimation was found greater in Mother-Infant sex class compared to other orangutan studies areas, such as Peat Natural Laboratory, and CIMTROP-UPR which reported a flanged male HR Size reaching 250 Ha per annum. We have found that the ranging pattern significantly changes over the study period. However, during P1, the distribution area was located within the northern of AOI, while in the P2 have changed to the south-eastern part of the AOI. We concluded that the ranging pattern indeed follows the fruit availability as well as fine-scale habitat quality.

AbstractSpecies–environment relationships are often studied at large spatial scales, but effective conservation requires an understanding of local-scale environmental drivers and pressures. Widespread degradation and fragmentation of forests have increased the proportion of tropical mammal habitat that is affected by edge effects. Edge effects include greater exposure to anthropogenic disturbance and abiotic changes that synergistically influence how well populations can cope with climate change. We investigated relationships between distance to the forest edge, forest structure, microclimate and terrestrial mammal detections in a selectively logged forest at the boundary of Gunung Leuser National Park in Sumatra, Indonesia. We collected mammal detection data from motion-activated camera traps, microclimate data from automated climate data loggers and forest structure data from vegetation plots. Daily mean and maximum temperatures significantly decreased with distance from the forest edge, whereas tree height and minimum temperature increased. Mammal diversity was lower at the forest edge compared to the interior. Mammals were detected less frequently at the forest edge, although this relationship varied between mammal orders. Mammal detections were best explained by temperature, tree height and tree diameter at breast height. These results demonstrate that abiotic changes in forests brought on by edge effects have negative impacts on mammals, but these effects vary between mammal taxa because of differing sensitivities to human disturbance. Our findings highlight the importance of considering local-scale environmental drivers in determining species–environment relationships to identify key habitat features such as microclimate refuges that should be prioritized in ecosystem management.

Natural hybridization provides valuable insights into evolutionary processes, such as speciation and the forces driving or hindering it. Sulawesi tarsiers Tarsius dentatus and T. lariang hybridize within a limited area, suggesting selection against hybrids. Their species- and sex-specific duet songs might serve as a premating barrier in sympatry, especially if differences are strengthened by character displacement. Individuals of mixed origin might face disadvantages if they inherit intermediate song traits. To shed light on the processes shaping this hybrid zone, we analysed 55 duet songs from within and outside the zone. For females and males, we identified temporal and frequency-related parameters that differ between species. We inspected hybrid songs for intermediate characteristics and analysed purebred songs for character displacement in sympatry. Female hybrid songs (N = 2) were intermediate in four to five of six parameters; interpretation of male hybrid songs (N = 2) was inconclusive, because only two parameters were reliably quantifiable. There was no character displacement in female songs in sympatry (N = 11) compared with monospecific areas (N = 17). In male songs, interspecific differences in note rate were significantly larger within the hybrid zone (N = 8) compared with outside (N = 13). Intermediate song traits indicate inheritance and may disadvantage hybrids during mate choice. Character displacement in male songs is consistent with female mate choice, because females should opt for unmistakable signals to avoid costly hybridization. Our findings thus suggest that duet songs of T. lariang and T. dentatus play an important role in limiting this hybrid zone.

Wildlife poaching and illegal trade threaten the survival of many rare species. We assessed spatiotemporal patterns in illegal killing, injury, capture, possession, and sale of orangutans, as well as law enforcement efforts, and conservation interventions affecting Critically Endangered orangutans in Indonesia from 2007 to 2019 using data collected from published and unpublished sources. We found 2229 reported crimes during the study period, including killing and non-lethal crimes. Annual crime rates did not show a declining trend overall during the study period. Most crimes, 99.6 % for Bornean orangutans (Pongo pygmaeus), and 95.7 % for Sumatran (P. abelii) and Tapanuli (P. tapanuliensis) orangutans combined, involved local not international trade. A total of 22 court cases (0.9 %) related to 2229 reported crimes; 20 of these cases led to convictions. At expected detection rates of less than 10 %, average estimated species mortality from killing was 14.3 % for Tapanuli and Sumatran orangutans combined, and 5.1 % for Bornean orangutans. This exceeds the 1–2 % orangutan hunting mortality threshold expected to drive populations to extinction. National parks with orangutans had 0.28–2.11 enforcement officers per 100 km2, below the 3–11 officers per 100 km2 considered global best practice to deter poaching. The most prevalent interventions to address orangutan crime—education and handovers of illegally held animals—have been conducted without an associated decline in crimes. These tactics alone are insufficient to address orangutan-related crimes. Substantial increases in patrols, investigations, arrests, and convictions, as well as community-focused solutions are urgently needed to halt orangutan killing and trade.

Conservation strategies are rarely systematically evaluated, which reduces transparency, hinders the cost-effective deployment of resources, and hides what works best in different contexts. Using data on the iconic and critically endangered orangutan (Pongo spp.), we developed a novel spatiotemporal framework for evaluating conservation investments. We show that around USD 1 billion was invested between 2000 and 2019 into orangutan conservation by governments, nongovernmental organizations, companies, and communities. Broken down by allocation to different conservation strategies, we find that habitat protection, patrolling, and public outreach had the greatest return on investment for maintaining orangutan populations. Given the variability in threats, land-use opportunity costs, and baseline remunerations in different regions, there were differential benefits per dollar invested across conservation activities and regions. We show that although challenging from a data and analysis perspective, it is possible to fully understand the relationships between conservation investments and outcomes and the external factors that influence these outcomes. Such analyses can provide improved guidance toward a more effective biodiversity conservation. Insights into the spatiotemporal interplays between the costs and benefits driving effectiveness can inform decisions about the most suitable orangutan conservation strategies for halting population declines. Although our study focuses on the three extant orangutan species of Sumatra and Borneo, our findings have broad application for evidence-based conservation science and practice worldwide.

Previous genetic studies of orangutans (Pongo spp.) have relied mainly upon mitochondrial DNA or microsatellite short tandem repeats (STR) for genomic genotyping analysis. Scientists have yet to take advantage of the genetic closeness of the great apes to humans for genomic analysis by using advanced techniques available for human genotyping. To genotype orangutans at Tanjung Puting National Park, we developed a novel combination of a methyl-based magnetic enrichment capture of genomic fecal DNA with genotyping on a human targeted single nucleotide polymorphism (SNP) microarray, and compared this to additional microsatellite (STR) micro-capillary genotyping. We successfully isolated 125 known human genomic SNP loci (0.08% of those targeted) which hybridized orangutan DNA on the human targeted Illumina Infinium QC array. We estimated genetic diversity and relatedness (r) using three estimators for a total of 32 (21 female and 9 male) wild orangutans at the Camp Leakey study site. Average TrioML relatedness within the sample, estimated from our combo SNP/STR dataset, was at a range consistent with half and first cousins (r = .082). All sampled males and females had relatives within the study site indicating we have verified a local, closely related community of wild orangutans at Camp Leakey.

Critically Endangered orangutans are translocated in several situations: reintroduced into historic range where no wild populations exist, released to reinforce existing wild populations, and wild-to-wild translocated to remove individuals from potentially risky situations. Translocated orangutans exposed to human diseases, including Coronavirus Disease 2019 (COVID-19), pose risks to wild and previously released conspecifics. Wildlife disease risk experts recommended halting great ape translocations during the COVID-19 pandemic to minimize risk of disease transmission to wild populations. We collected data on orangutan releases and associated disease risk management in Indonesia during the COVID-19 pandemic, and developed a problem description for orangutan disease and conservation risks. We identified that at least 15 rehabilitated ex-captive and 27 wild captured orangutans were released during the study period. Identified disease risks included several wild-to-wild translocated orangutans in direct contact or proximity to humans without protective equipment, and formerly captive rehabilitated orangutans that have had long periods of contact and potential exposure to human diseases. While translocation practitioners typically employ mitigation measures to decrease disease transmission likelihood, these measures cannot eliminate all risk, and are not consistently applied. COVID-19 and other diseases of human origin can be transmitted to orangutans, which could have catastrophic impacts on wild orangutans, other susceptible fauna, and humans should disease transmission occur. We recommend stakeholders conduct a Disease Risk Analysis for orangutan translocation, and improve pathogen surveillance and mitigation measures to decrease the likelihood of potential outbreaks. We also suggest refocusing conservation efforts on alternatives to wild-to-wild translocation including mitigating human-orangutan interactions, enforcing laws and protecting orangutan habitats to conserve orangutans in situ.

Abstract. Rambey R, Susilowati A, Rangkuti AB, Onrizal O, Desrita, Ardhi R, Hartanto A. 2021. Plant diversity, structure and composition of vegetation around Barumun Watershed, North Sumatra, Indonesia. Biodiversitas 22: 3250-3256. Watershed ecosystem plays an important role in water and soil conservation which is supported by vegetation around watershed. As such, vegetation analysis is beneficial to assess the current state of watershed vegetation and monitor future changes. Barumun Watershed, located in South Labuhanbatu District, North Sumatra Province, Indonesia, is under threat due to habitat degradation and land conversion for plantation and agriculture. This research aimed to investigate the diversity, structure and composition of vegetation in the Barumun River including its smaller streams (rivulets). Data were collected using a combination of line transect and quadratic plots arranged systematically. The total observation plots were 48 plots, consisting of 24 plots in Barumun River, 12 plots in Tasik Rivulet and 12 plots in Titi Kembar Rivulet. The results documented a total of 51 plants in the studied sites in Barumun Watershed in which 37 species were found in Barumun River, 20 species in Tasik Rivulet and 17 species in the Titi Kembar Rivulet. Plant species consisted of several habitus including herbs, palms, shrubs, climbers and trees. The trees consisted of 22 species (43.13%), herbs 22 species (43.13%), climbers 3 species (5.88%), shrubs two species (3.92%), and palm two species (3.92%). The highest Importance Value Index (IVI) for tree community was recorded in the Barumun River from Hevea brasiliensis (108.28), followed by Cryptocarya sp. (123.24) in the Titi Kembar Rivulet. In addition, the highest IVI for pole, sapling, seedling, and shrub was recorded from Muntingia calabura (Barumun River), Nauclea orientalis (Tasik Rivulet), Psychotria viridiflora (Tasik Rivulet), and Calamus axillaris (Titi Kembar Rivulet), respectively. The plant diversity in Barumun Watershed was categorized from low to moderate level of richness.

For decades, mangrove forests have been under tremendous pressure due to deforestation and conversion. To sustainably manage the mangroves that remain, an ecosystem approach to management is essential. Two different management regimes – conservation and restoration – were assessed, looking at their respective effects on forest structure and carbon cycling capacity, when compared with degraded mangrove. We found that mangrove restoration enhanced tree density, while mangrove conservation was able to maintain species diversity. In terms of carbon budgets, aboveground carbon was lower in restored mangrove (79.40 ± 37.41 Mg C ha−1) when compared with conserved mangrove (92.26 ± 22.65 Mg C ha−1), but was almost double that found in degraded mangrove (39.89 ± 27.49 Mg C ha−1). Although conserved mangrove had higher aboveground carbon, lower amounts of soil carbon were found in conserved mangrove (127.49 ± 33.21 Mg C ha−1) than in restored and degraded mangrove (236.26 ± 20.33 Mg C ha−1 and 139.17 ± 25.44 Mg C ha−1, respectively). The elevation change was highest in degraded mangrove (41.7 ± 24.0 mm yr−1), followed by restored (20.7 ± 14.6 mm yr−1) and conserved mangrove (12.2 ± 3.9 mm yr−1). Carbon burial in conserved mangrove (1.20 ± 1.90 Mg C ha−2 yr−1) was double that of degraded mangrove (0.63 ± 0.60 Mg C ha−2 yr−1). Ultimately, we conclude that although a conserved mangrove is not always the end result of mangrove restoration and sustainable management, finding balance between structural development and ecosystem function is essential to serve different objectives, including biodiversity maintenance.