Abstract: In Japan, the raccoon (Procyon lotor) is an invasive alien species that causes ecological and agricultural damage nationwide. Trapping is typically conducted to limit agricultural damage, even when performed on the basis of the Invasive Alien Species Act. Local government officials are expected to play leading roles in local trapping efforts; however, few municipal initiatives have reduced raccoon populations to adequately low densities. This study examined the enhanced countermeasures undertaken by a municipality in Japan and their efficacy in reducing the local raccoon population. The study area was Shintotsukawa in Hokkaido, Japan, where enhanced raccoon capture measures were implemented for 3 years beginning in fiscal year 2019. We compiled municipal data on the trapping efforts conducted, numbers of raccoons captured, and sex of individual raccoons. Both the trapping efforts and the number of captures increased after fiscal year 2019; the raccoon population density index decreased each year, with an estimated population of 0.840 raccoons/km² in fiscal year 2021. To enhance capture measures, three activities were undertaken: improvements to the capture program such as the introduction of capture grants and increasing the number of box traps available for rent, raccoon distribution surveys and capture support by town officials, and public awareness campaigns. Overall, the number of box trap applications increased due to the availability of rental box traps and capture grants, which enhanced trapping efforts. Although no numerical evidence could be obtained, the public awareness campaigns likely also supported the enhancement of trapping efforts. These results imply that improving municipal resources (e.g., workforce, goods, money, and information) can greatly promote the control of raccoon populations. Capture as a means of preventing agricultural damage represents only one measure employed to combat invasive alien species. However, as shown in this case study, enhancing the resources available to local authorities can stimulate local trapping activities and assist in eradication efforts. Sharing the outcomes of such cases will encourage more local authorities to improve capture programs according to their unique situations.

Abstract: Because primates and large birds can be the sole seed dispersers for plants with large seeds or fruits, as well as being the seed dispersers of a wide variety of other plants, seed dispersal collapse in defaunated forests has become a concern. In Japan, a dramatic reduction in the seed dispersal of Morella rubra has been reported on Tanegashima Island, where its main seed disperser, the Japanese macaque (Macaca fuscata), has become extirpated, unlike on Yakushima Island, which is still inhabited by Japanese macaques. A previous study of seed dispersal collapse focused on arboreal animals that consume M. rubra fruits in the canopy; however, secondary seed dispersal of M. rubra by terrestrial animals remains unclear. The objective of this study was to identify animal species that consume fallen M. rubra seeds and fruits on Yakushima and Tanegashima islands, and to explore the possibility of secondary seed dispersal by these animals. In June 2022 and 2023, we established infrared-triggered cameras at experimental M. rubra fruit patches at 10 sites each on Yakushima and Tanegashima islands, and recorded the terrestrial animal species that visited the sites, together with their visitation frequency. All individuals that consumed or removed fruits were considered foragers, and their species and the numbers of fruits foraged were recorded. The results show that seven animal species on Yakushima Island and ten on Tanegashima Island visited M. rubra seeds or fruits, including five foragers, Japanese macaques, Cervus nippon, Apodemus spp., Nyctereutes procyonoides, and Corvus macrorhynchos, with C. nippon and Apodemus spp. accounting for the highest foraging rates. Considering their feeding style and small faeces, C. nippon may chew M. rubra seeds when feeding on the fruits, and are therefore unlikely to contribute to secondary seed dispersal. By contrast, Apodemus spp. were observed to consume the fruit pulp and seeds, and sometimes held the fruits in their mouths before removing them. This behaviour implies that Apodemus spp. may hoard M. rubra seeds, which could play an important role in the secondary seed dispersal of M. rubra, particularly on Tanegashima Island, where Japanese macaques are absent. Future studies should comprehensively evaluate the amounts of dispersed seeds, seed dispersal distances, and survival and germination rates of dispersed seeds to reveal the role of Apodemus spp. as a secondary seed disperser of M. rubra.

Abstract: Ongoing construction activities are impacting the Tokusagawa River, which runs through the cities of Takizawa and Morioka in Iwate Prefecture, Japan. To elucidate and mitigate the impacts, efforts are being made to investigate the distribution of the endangered herb Primula sieboldii, and to preserve strains of the plant originating from the construction area. Observations of P. sieboldii plants have revealed many instances of insects puncturing fruit to reach the seeds within; thus, in this study, we examined the effects of such feeding damage on seed production in the Tokusagawa population of P. sieboldii. Fewer than 20% of fruit were intact, with genet averages of 14% in 2020 and 18% in 2021; 29% of enlarged fruits were damaged by feeding in 2020, and 18% in 2021. In the neighbouring Shizukuishi population, 40% of fruit were intact in 2021 and 6% of enlarged fruits were damaged. This implies that the negative effects of feeding by herbivorous insects—an antagonistic biological interaction—may be more pronounced in the Tokusagawa population. We found several lepidopteran larvae consuming seeds inside fruits, and chrysalises around damaged fruits and peduncles. The insect was identified as the plume moth Amblyptilia punctidactyla. Feeding by A. punctidactyla fluctuated between genets and years; consequently, P. sieboldii from Tokusagawa may remain able to produce seeds and maintain genetic diversity. Although we do not yet see a need to implement urgent conservation measures, such as artificial pollination or bagging to protect fruit, it is important to continue monitoring seed production. Local ecosystems naturally include antagonistic interactions among organisms, and effective ecosystem conservation must reflect this. To this end, it is also important to recognise A. punctidactyla as a component of the local ecosystem along with P. sieboldii, and to continue monitoring the effects of ongoing environmental modification on both the species of the Tokusagawa area and their interactions.

Abstract: With the recent decline in biodiversity, many organisms face endangerment or extinction. Ex-situ conservation, reinforcement, and reintroduction to wild habitats are common conservation strategies for endangered species. However, these practices risk population disruption due to inbreeding depression and adaptation to captive environments. These issues should be addressed through the application of conservation genetics methods. In recent years, many endangered species conservation policies have been based on the outcomes of conservation genetics studies. In this work, we summarise recommendations for the ex-situ conservation, reinforcement, and reintroduction of endangered species from a conservation genetics perspective. We include discussions of inbreeding depression and adaptation to captive environments, which are often problems in ex situ conservation and reintroduction. We also consider risk assessments of genetic disturbance and the importance of genetic monitoring after reinforcement or reintroduction. Although only a few case studies based on conservation genomics have been published, their findings are expected to be essential for biodiversity conservation, such as inbreeding depression risk assessments and population demography estimations.

Abstract: Distinguishing correlation from causation when evaluating factors threatening wild populations of organisms is crucial for the implementation of effective conservation measures. However, few studies in the field of conservation ecology have applied a causal inference framework to evaluate wild populations. In this study, we applied an integrated causal inference approach to explore the relationship between insecticide use and population decline, using the dragonfly Sympetrum frequens (Selys), which is among the most common dragonflies in Japanese paddy fields, as an example. In the late 1990s, S. frequens populations declined sharply in many regions. The main cause of these declines is suspected to have been the use of systemic insecticides such as the neonicotinoid imidacloprid and the phenylpyrazole fipronil, which were widely used in rice seedling nursery boxes. These insecticides were introduced immediately before the S. frequens population decline began, and subsequent laboratory- and field-based analyses have shown them to be highly toxic to dragonfly nymphs and other invertebrates. However, a causal relationship between insecticides and the decline of S. frequens has not been systematically determined, mainly due to the limited availability of quantitative data on species population size and habitat characteristics over the period of decline. Given these limitations, we applied five different approaches to investigate the relationship between insecticide use and S. frequens populations, as follows. First, we conducted a review of evidence based on currently available information, followed by the application of a statistical causal inference model using available insecticide usage and dragonfly monitoring data. Next, we conducted a field experiment to assess the effects of a novel insecticide on S. frequens and evaluated the effects of climate warming as a potential alternative explanation for the decline of S. frequens. Finally, we performed a mechanism-based evaluation of the effects of each factor using a population model. Our results suggest that the sharp population declines of S. frequens in the late 1990s were caused by the combined effects of highly toxic insecticides and habitat degradation due to its conversion to well-drained paddy fields.

Abstract:　In ecological studies, methods used in other fields to elucidate causal relationships, such as randomized controlled experiments and large-scale computer simulations, may not be feasible or effective. However, the availability of large-scale data generated in ecosystem monitoring is dramatically increasing. Accompanying this recent trend are growing expectations for the development of methods to elucidate causal relationships in a data-driven manner. CCM, proposed by George Sugihara et al. in 2012, has led ecologists to focus on causal estimation by time series. On the other hand, Granger causality and information theoretic approaches have also developed as important methods for dealing with causality in dynamical systems. Time series based causal analysis is based on a wide range of fields, and it is necessary to properly understand the advantages and disadvantages of each method in order to use them appropriately. In this paper, we propose that by introducing a unified perspective through information theory, Granger causality deals with momentary information imbalances, whereas CCM deals with those in the larger temporal structures represented by attractors. From this perspective, technical complementarity is recognized, while a new challenge of the multifaceted nature of causality emerges for the study of ecological dynamics. Thus, the elucidation of causality in ecological systems will progress by developing new approaches from a broad perspective that transcends domain boundaries and confronts real-world complexity.

Abstract：Trillium camschatcense, listed as ‘vulnerable’ in the IUCN Red List, is a perennial plant growing in the understory of broad-leaved deciduous forests of northern Japan. While we have been monitoring the demography of three southernmost populations in Iwate and Akita Prefectures since 2013, there has been a rapid increase in the number of Japanese sika deer in Iwate. In this report, we analyzed changes in the populations during 2013–2022 to examine the impact of deer browsing. We found that the two Iwate populations have shown an increase in per capita herbivory rates since 2017. Infrared cameras suggest that the main herbivore responsible is the Japanese sika deer. Compared to reproductive plants that were not consumed by deer, consumed plants were more likely to regress to the three-leaf stage (nonreproductive stage) in the following season. Consequently, the proportion of the three-leaf stage markedly increased since 2019, and the number of reproductive plants has decreased to only three individuals each in 2022. In contrast, herbivory rates and the proportion of the three-leaf stage did not show notable changes in the Akita population, where the increase of deer is not as pronounced. In Iwate, many individuals that were previously in the flowering stage have not died and are still surviving in the nonreproductive stage, suggesting that we may currently be in the early stage of deer overbrowsing. Given that Trillium populations are highly susceptible to and among the first to be affected by deer browsing, their impact on understory vegetation may further increase in the near future.

Abstract: The rare orchid Calanthe discolor is on the verge of extirpation from Japan due to foraging by the agromyzid fly Japanagromyza tokunagai and the decline of pollinator bees. Artificial pollination and bagging treatments that exclude foraging flies are promising conservation measures. We examined the rates of fruit set and ripe seed production resulting from the artificial pollination and bagging of C. discolor at five field sites in Fukui Prefecture, Japan. We tested 24 individuals over 2 years from 2021 to 2022, classified into three treatment groups: 1) no artificial pollination + no bagging (13 individuals), 2) artificial pollination + no bagging (5 individuals), and 3) artificial pollination + bagging (6 individuals). Artificial pollination resulted in an average of 5 fruits per individual (range: 1–9 fruits), while untreated plants produced only 0.2 fruits on average (range: 0–2 fruits; Wilcoxon rank sum test, p < 0.0001). Additionally, the average percentage of each plant damaged by flies such as J. tokunagai was 0% in the bagged group and 56% (range: 0–100%) in the untreated group (Wilcoxon rank sum test, p < 0.01). Thus, both artificial pollination and bagging of C. discolor produced statistically significant improvements in fruit set and ripe seed production. Our results suggest that pollination opportunities are reduced in untreated C. discolor, with serious implications for the species’ ongoing reproduction and survival.

Lake Kasumigaura in Ibaraki Prefecture, Japan provides various ecosystem services to residents of the basin and the surrounding area. We applied a zonal travel cost method to assess the recreational value of the lake in monetary terms. We conducted an online questionnaire survey across Japan, and asked participants if they were interested in the water quality and organisms of Lake Kasumigaura, and whether they had visited any of the six recreational spots on the shores of Lake Kasumigaura (mainly the Nishiura and Hitachi Tone Rivers) during 2017. Among those who had visited any of these attractions, we asked for the subject’s home prefecture (if visiting from outside Ibaraki Prefecture) or municipality (if visiting from within Ibaraki Prefecture). We calculated the visit rate and travel costs to each attraction at Lake Kasumigaura. The results were used to determine the demand curve for the lake, and the consumer surplus per visit was calculated to be 4,087 yen/person. Then, we calculated the recreational value of Lake Kasumigaura based on the product of the consumer surplus and the annual number of visitors to Lake Kasumigaura. Thus, the recreational value of the lake was estimated to be 24.6 billion yen/year.

To monitor the condition of beech canopies in a reproducible, recordable, and labour-efficient manner, we investigated flight planning, aerial photography, and structure-from-motion (SfM) processing techniques to generate orthoimages with accurate positioning using non-real-time kinematic (RTK) unmanned aerial vehicles (UAVs) in mountainous regions where Internet access is restricted. The automated UAV flight maintained a consistent altitude. The data encompassed a 20-ha region on the summits of Mt. Tanzawa and Mt. Hirugatake in the Tanzawa Mountains, and were acquired during July and August of 2021 and 2022, with a ground resolution of 2 cm/pixel. The directly downward photos had a parallel perspective with overlap and side-wrap percentages of 80% and 60%, respectively. The oblique-perspective images had a parallel view, with the camera lens tilted 20° or 30° forward, accompanied by overlap and side-wrap percentages of approximately 40% and 30%, respectively. Ground control points (GCPs) and verification points were established using the precise point positioning (PPP)-RTK method with a dual-frequency global navigation satellite system (GNSS). A virtual reference station received correction signals via the quasi-zenith Michibiki satellite. The GCPs were located in areas with an unobstructed view of the sky, while the validation points were placed at terrestrial features, such as on a staircase or bench along a mountain trail. The study involved manipulating aerial photographs and using GCPs for SfM processing, with variable SfM processing quality. The objective was to compare the clarity and positional accuracy of the orthoimages and a three-dimensional (3D) surface-point cloud obtained through SfM processing. High-quality SfM processing and GCP correction using both nadir and oblique imagery produced colour orthoimages and a 3D surface-point cloud with spatial coordinate accuracy within 0.3 m. The resulting images had satisfactorily clear views of exposed branches and missing canopy material, ensuring dependable canopy identification and tracking. This method proved effective for monitoring and comparing individual trees over time, although some issues remain, such as lens calibration and identifying the optimal GCP locations.