The generation of wind power negatively impacts bird and bat species. Therefore, bird sensitivity maps are important tools for conserving biodiversity while promoting the development of renewable energy. This special issue was created in response to Symposium S03 (“Toward the Dissemination of Sensitivity Maps to Prevent Bird Collisions”), which was held at the 65^th Annual Meeting of the Ecological Society of Japan in 2018. In this special issue, seven experts at the forefront of research on the environmental impacts of wind power on birds provide their perspectives on the utility and challenges of bird sensitivity mapping.

The Japanese government has pledged to achieve carbon neutrality by 2050. To realise this goal, renewable solar, wind, hydro and geothermal power generation are now attracting attention. Wind power is expected to have great potential in Japan, and is likely to be promoted on land and sea areas. However, with the introduction of wind power generation throughout Japan, associated environmental conflicts are expected to increase. The main points of contention are noise, infrasound, landslides, water pollution, landscape aesthetics, the natural environment and birds, especially bird collisions and habitat abandonment caused by the construction of wind turbines in the habitat of rare birds of prey, such as the golden eagle Aquila chrysaetos, Hodgson's hawk eagle Nisaetus nipalensis and the white-tailed eagle Haliaeetus albicilla. Environmental conflicts are likely to increase as wind power projects are developed, to achieve the 2050 target. Therefore, the use of sensitivity maps should help prevent bird collisions and habitat abandonment. A sensitivity map shows where birds are likely to be negatively affected by the construction of wind power facilities, based on integrated information on the habitat of endangered bird species, migratory bird flyways, colony sites, overwintering areas, protected areas, etc. This review first explains the concept of a sensitivity map and describes its relation to environmental assessments. Then, we explain the features of various proposed sensitivity maps and discuss their appropriate resolution. Finally, we discuss the roles of sensitivity maps in future efforts to reconcile biodiversity conservation and the anticipated demand for renewable energy development, to attain the 2050 carbon-neutral target.

In recent years, wind-power facilities have been rapidly constructed along the Japanese coastline, from Northern Hokkaido to Tohoku. This area is a wintering and stopover zone and coincides with a major flyway for migratory geese and swans. Wind farm construction can directly and indirectly affect migratory birds through habitat loss, abandonment of wintering sites, direct mortality, and increased energy costs resulting from detours to avoid such facilities. Sensitivity maps visualising areas of greater collision risk to migratory birds represent a powerful tool for habitat conservation, while continuing to encourage renewable energy development. In this review, we first outline the current state and relevant issues of sensitivity mapping for large waterfowl, then provide two sensitivity maps for Middendorf’s bean goose. The first map provides a sensitivity score based on the probability of a goose flight path intersecting with the turn area of a windmill blade at wintering and stopover sites, and the second map shows the predicted altitudes of geese flight paths based on landscape and topographic factors along the major migratory route. Finally, we propose a systematic approach to assess putative wind farm locations, considering the outcomes of sensitivity mapping.

To minimise the impacts of marine wind farms on seabirds, early planning stages should incorporate sensitivity mapping. In this review, we discuss sensitivity map development and explore associated problems and applications. Large-scale sensitivity maps display seabird distribution densities collected by boat and aerial surveys over multiple years, during various seasons and in several geographical areas; small-scale maps display tracking data for breeding seabird populations during the breeding period. Using distribution densities, the sensitivity maps are constructed by incorporating a species-specific index of risks (i.e. flight height) and an index of conservation status. Large-scale maps can be constructed easily if extensive and long-term seabird distribution data are available. Small-scale maps display the sensitivity of target populations associated with wind farm construction at fine temporal and spatial resolutions. Currently, the number of applicable species are limited due to methodological restrictions. As the methods for species tracking advance, small-scale maps will become easier to produce. Incorporation of the habitat model to a small-scale map allows for feeding site and flight path prediction for target populations in particular years or geographies, yielding a versatile prediction tool. For both map types, the risks of collision and displacement are evaluated individually; therefore, the establishment of a sensible integration method is needed.

The white-tailed eagle is susceptible to negative effects related to wind farms. Wind-farm locations must be carefully selected to avoid danger to these eagles and thus mitigate impacts. However, the distribution of this species at broad scales is poorly understood, which hinders such planning. We created a predictive model of the potential breeding area of white-tailed eagles in northern Hokkaido, Japan. Using Maxent, we constructed a spatial model using 43 nest locations and 6 environmental variables, then evaluated the model using 12 withheld nest locations. The distribution of breeding habitat was highly correlated with topographic factors at the local scale and with land-use types at the home-range scale, indicating that eagles select habitat at multiple spatial scales. Habitat suitability was higher in places with more moderate forest cover and mid-sized water bodies at the 2-km scale, with dense forest edges at the 3-km scale, and at lower elevations at the 0.1-km scale. Model performance was relatively high, implying that our suitability map could be used to create a sensitivity map. The habitat-suitability map shows areas of northern Hokkaido that are important breeding habitat for white-tailed eagle; we do not recommend wind-farm establishment in these places.

The construction of wind power farms is expected to impact bird habitat. In Europe, nature conservation groups have created sensitivity maps prior to wind farm construction, allowing for some impacts to be avoided during the planning stage. The Wild Bird Society of Japan undertook a similar task for the northern portion of Hokkaido; proposed and existing wind farms, rare bird habitat, and migratory flyways overlap in this area. Here, we detail the process used to create a sensitivity map. First, we compiled informal literature review of sensitivity mapping approaches both within and outside of Japan. Then we consulted with experts and local stakeholders to select a methodological approach for our study region and applied that approach to data collected from multiple field surveys. Twenty-three bird species were targeted for sensitivity mapping and our resulting map included 84 grid cells of 5 × 5 km each. Our results suggest that bird species will be most vulnerable to wind farm construction in the western and northern portions of the study area. This is due to the occurrence of endangered bird habitat and migratory routes for sea eagles, geese, and swans in this area.

Japan's decarbonization efforts incorporate renewable energy technologies and other carbon-reducing measures. The installation of wind power facilities is associated with fatal bird strikes. Thus, it is important to implement biodiversity and con-servation strategies as societies make changes to reduce carbon emissions. To address this concern, the Ministry of the Environment created sensitivity maps to identify areas with a high rate of bird strikes. The development of detailed bird strike risk assessments requires significant time and effort; however, the construction of renewable energy power facilities is already underway. Therefore, it is not feasible to postpone sensitivity map production until a fully mature risk assessment is completed. Here, we describe the creation of a feasible sensitivity map using currently available information.

This paper examines risk management with a focus on scientific uncertainty. The impact of wind power generation on birds was used as an example because this is a trans-science problem that cannot be solved by science alone. The ideal form of uncertainty was categorised using the scale of knowledge for the results and knowledge of probability, and countermeasures were presented accordingly. The paper also examines the framework of stakeholder recognition in decision-making and states that the preconditions can be changed not only by reducing the environmental impact but also by proactively contributing to nature restoration.

Abstract: Many Japanese freshwater fish species, including bitterlings, are at risk of extinction due in part to invasive species such as largemouth bass (LMB), northern snakehead, and continental rosy bitterling. To protect local ecosystems, it is necessary to evaluate the direct and indirect effects of invasive species and prioritize which to control. However, such work is challenging, and few studies have comprehensively assessed the effects of multiple invasives on local fish communities, including rare species. In this study, we conducted environmental DNA (eDNA) metabarcoding in 35 holding ponds in the Omono River basin in Akita Prefecture, northern Japan. Non-metric multidimensional scaling (NMDS) analysis showed that LMB had a major effect on the fish-community structures of these ponds. Average fish species richness and Shannon-Wiener diversity were both ca. 40% lower in ponds where LMB eDNA was detected than in those where it was not. Additionally, eDNA revealed a significant association between continental rosy bitterling and endemic bitterlings, implying potential resource competition. On the other hand, we found no significant association between LMB or northern snakehead and endemic bitterlings, while the chestnut goby had a significant negative association with LMB. The eDNA concentrations of endemic bitterlings were inversely associated with the presence of eDNA from the three invasive species, indicating that the invasives had a strongly negative effect on endemic bitterling biomass: average eDNA concentrations of endemic bitterling at sites where the invasives’ eDNA was detected were just 2.4% (continental rosy bitterling), 6.6% (LMB), and 8.0% (northern snakehead) of the levels where no invasives were detected. These results imply that exterminating and preventing the spread of LMB are top priorities for maintaining these pond ecosystems, and that appropriate management and monitoring of continental rosy bitterling and northern snakehead are also important in ponds where rare endemic bitterlings coexist.

Hitoshi Sakio^1,*, Kokoro Kamimura², Yosuke Nakano³ Robinia pseudoacacia, introduced from North America to the upper reaches of some Japanese rivers, has since expanded its distribution downstream to the middle and lower reaches, greatly affecting the community structure, landscape, and biodiversity of natural riparian forests. However, on the Ina River in Tadami, Fukushima Prefecture, R. pseudoacacia prevails along the upper and middle reaches but is nearly absent from the lower reaches, where a riparian forest dominated by willow species such as Salix dolichostyla subsp. dolichostyla and S. hukaoana has formed. To elucidate the reasons for the absence of R. pseudoacacia, we experimentally examined the water tolerance of seedlings and reproductive ability of branch fragments from R. pseudoacacia and several willow species. To compare water tolerance, we conducted submergence and stagnant water experiments using current-year seedlings of R. pseudoacacia and S. dolichostyla subsp. dolichostyla. We also compared root and shoot development in both water and soil using cuttings from nine tree species, including R. pseudoacacia and several willows. In the submerged environment, all current-year R. pseudoacacia seedlings died in only 4 days, whereas 60% of current-year S. dolichostyla subsp. dolichostyla seedlings survived even after 10 days. The growth of S. dolichostyla subsp. dolichostyla was not affected by water retention, whereas the growth of R. pseudoacacia was greatly reduced and rhizome formation greatly inhibited. The R. pseudoacacia cuttings failed to root in both water and soil, and though shoot emergence was observed from branches inserted into soil, all shoots eventually died. Conversely, Salix udensis and S. dolichostyla subsp. dolichostyla showed high root and shoot development in both water and soil. Salix hukaoana diverged in showing little rooting and limited shoot development. These results suggest that R. pseudoacacia is intolerant of submergence and waterlogging, and is unlikely to reproduce via branch fragments under these conditions. Conversely, S. dolichostyla subsp. dolichostyla was highly water tolerant, and both it and S. udensis reproduce vegetatively via branch fragments, while S. hukaoana is less likely to do so. The near-complete absence of R. pseudoacacia and the dominance of willows in the lower Ina River watershed is largely attributable to the difference in young plant flooding tolerance.

Pistia stratiotes, a free-floating aquatic plant of the Araceae, is regulated under the Invasive Alien Species Act of Japan as a highly invasive species. However, the species has been historically recorded from the Ryukyu Archipelago, where it is a doubtful alien species. Here, I re-evaluated the alien status of P. stratiotes through a review of literature and specimen records. The oldest distribution records of P. stratiotes in Japan were based on specimens and an 1854 manuscript by C. Wright, who recorded it as common in paddy fields. Prior to the 1950s, several researchers recorded that the species was distributed from Okinawa Island southward to the Yaeyama Islands, and grew primarily in and around paddy fields, coexisting with many native aquatic plants. Furthermore, several authors treated P. stratiotes as native, and none treated it as exotic between 1890 and 1950. The earliest opinion of P. stratiotes as invasive was in a specimen label described by E. Walker et al. in 1951. Since the 1970s, the treatment of P. stratiotes as exotic has become common without any scientific evidence. Horticultural use of the species began in the 1930s and became commonplace by the 1950s. By the 1970s, the species had begun to naturalise on the Japanese mainland. All Japanese populations of P. stratiotes may have been determined to be exotic without sufficient evidence because older information, such as unpublished manuscripts, was difficult to access until recent digitisation made it open to the public; and researchers’ judgment may have been biased because of several pieces of information, such as the hypothesis of the species’ African origin. Based on the above, the populations of P. stratiotes that have been found in the Ryukyu Archipelago since before the 1850s cannot be considered exotic based on available scientific evidence, and recent molecular phylogeographical findings suggest that they may comprise a natural distribution. These populations may be threatened by shrinking habitat and by competition and hybridisation with the introduced lineage of P. stratiotes. For appropriate regulation under the Invasive Alien Species Act, taxonomic studies and methods to distinguish these P. stratiotes lineages, as well as an understanding of their current habitat conditions, are needed.

The Japanese red pine form utsukushimatsu (Pinus densiflora Siebold et Zucc. 'Umbraculifera') is characterised by a trunk composed of numerous stems of similar diameter. It occurs only in Hiramatsu, southern Shiga Prefecture, western Japan, where it is preserved as a natural monument. However, wilt disease has caused high tree mortality in this species, decreasing the population from 450 in 1924 to 86 in 2019. To obtain population genetic data for conservation, we collected 236 samples from seedlings, saplings, and mature trees in the utsukushimatsu forest and experimental plantations. We performed multiplexed inter-simple sequence repeat genotyping by sequencing and found no clear genetic differentiation between the common Japanese red pine and its utsukushimatsu form. This suggests that the Hiramatsu red pine population has a genetic mutation that causes the utsukushimatsu form in individuals homozygous for this gene, consistent with previous reports. Inbreeding was observed in the native populations. Conservation of the utsukushimatsu habitat requires the maintenance of a population made up of individuals of all life stages (seedlings to adults); therefore, understory management through frequent undergrowth thinning is essential. Monitoring surveys should be conducted for in situ plant conservation, and seeds from various mother trees should be sown to reduce inbreeding in ex situ plant conservation.

Migratory bird populations have been declining globally for several decades. Migratory species are vulnerable to decline due to the variety of habitats they require over their lifetimes, including breeding, overwintering, and stopover sites. Degradation and loss in any of these habitats may threaten population survival. Preventing further declines in migratory bird species requires understanding their feeding habits across habitat types and utilising appropriate habitat management to prevent qualitative and/or quantitative declines in food resources. We assessed the feeding habits of two large waterfowl, the bean goose (Anser fabalis subsp. middendorffii) and tundra swan (Cygnus columbianus) using DNA barcoding and stable isotope analyses to inform habitat management and conservation efforts within their wintering grounds in Fukushima Lagoon, Niigata Prefecture, Japan. The bean goose overwintering diet consistently comprised Oryza sativa and Trapa natans. Tundra swans also consumed O. sativa as a primary food item, but shifted their consumption to other rice paddy plants, including Alopecurus aequalis and Poa annua, in November and December. Thus, these two species overlap in primary food items, but their utilisation differs during winter. In both species, food item use was dependent on plant species distribution within paddy fields and lagoons. Maintaining these migratory species in Fukushima Lagoon requires conservation efforts to integrate the lagoon and surrounding paddy fields as a foraging area.

Endemic plants on gravel bars along the river maintain populations in a balance between the creation of habitat by the formation of bare land in floods and the loss due to runoff, burial, and overgrowth of competing plants. In the middle reaches of the Tama River, restoration actions for the endangered plant Aster kantoensis Kitamura (AKP: Aster kanoensis Project) have been carried out for 20 years in partnership of citizens, public administration, and researchers. AKP began actions to reinforce the regional population in KUSABANA area (KUSABANA population, commonly known as once the largest population in the Tama River, which disappeared in 2015) in the experimental gravel riverbed developed downstream of KUSABANA population in 2002. The new local population in the sowing area with high relative height, expanded to the area with low relative height. The population in the sowing area, decreased due to the overgrowth of competing plants, so actions of weeding competing plants began in 2006. Most of the land in the area with low relative height, was bare due to a large-scale flood occurred in 2007. The individual settlement by wind dispersal of seed was promoted and the range of local population was expanded. Since 2015, the number of flowering individuals has decreased to less than 80　due to further overgrowth of competing plants in the sowing area. Furthermore, the number in the area with low relative height also, has decreased due to the small-scale floods with no bare ground. An unprecedented large-scale flood in 2019 caused the disappearance of all individuals in the experimental area. Accordingly, preserved seeds were reintroduced in 2020 and 2021, and 211 of flowering individuals were observed in the fall of 2021. Since 2017, sowing actions has been carried out in suitable areas other in addition to the experimental area. The rosette/flowering population ratio, which represents the growth capacity of the population, reached its maximum in the second year after bare land formation and began to decline in the third year, so the activities to remove competing plants for maintaining the population became overwork. There are also risks of extremely large flooding that cause the loss of entire local populations. For these reasons, rather than artificially baring a small area of a riverbed and introducing a population and maintaining it by weeding, it may be more realistic to sow it flexibly in a suitable habitat that is scattered throughout the riverbed and changes its distribution over time. AKP has been revising its activities according to the river environment and the growth conditions of the A. kantoensis with consolidating the information provided by public administration on river management plans, the knowledge of researchers to judge the growth status, and the work capabilities of citizen volunteers. In an ever-changing river environment, the organization like AKP with continuity and adaptability is effective.

Cervus nippon mageshimae Kuroda and Okada (mage shika in Japanese) is a subspecies of C. nippon described based on its morphology. Although recent genetic studies indicate the genetic uniqueness of C. n. mageshimae, its description in the 2014 Red Data Book suggests that its distribution and taxonomic position as a subspecies need to be clarified. In this study, we re-evaluated the validity of C. n. mageshimae with genetic data collected in previous studies. Our phylogenetic analysis revealed distinct sequence differences in mitochondrial DNA between C. n. mageshimae and both C. n. nippon on Kyushu and C. n. yakushimae from Yaku-shima and Kuchinoerabu-jima Islands. Previous analyses of nuclear and Y-chromosome DNA have also identified differences in allele frequencies between the Tanegashima and Yaku-shima Island populations. In addition, previous morphological studies demonstrated morphological differences between these islands. Overall, these findings suggest the presence of genetically distinct populations on Mage-shima and Tanegashima Islands that can be recognised as conservation units.

Largemouth bass (Micropterus nigricans) is listed among the world’s 100 worst invasive alien species by the International Union for Conservation of Nature (IUCN). Because of M. nigricans’ serious negative impacts on aquatic ecosystems that it invades, major efforts have been made to control and locally eradicate it. However, there are few reports of its complete eradication from lake or river systems. Here, we discuss a comprehensive program of M. nigricans eradication in Kanabara Dam Lake, Nagano Prefecture, Japan. Operating since 2007, the program includes the removal of spawning beds; removal of larvae and fry through scooping; and capture of immature and adult fish via net traps, cast nets, gill nets, fishing, and spear guns, and by hand. The M. nigricans population was monitored via snorkelling and environmental DNA analysis. Net traps were effective for capturing smaller fish, whereas 3-meter-long gill nets and spear guns were effective for larger fish. Yearly catches of M. nigricans reached a maximum of 1,472 in 2010, excluding young-of-the-year. The number of spawning beds reached a maximum of 131 in 2012 but decreased rapidly and substantially thereafter. In 2014 > 5,000 larvae were observed around a few spawning beds, having been missed at the time of spawning. Most of these larvae were quickly caught via hand nets from the shore or by snorkelling. Interestingly, Amur goby (orange type, Rhinogobius kurodai) increased in abundance during the eradication program and preyed upon M. nigricans eggs. We found no evidence of new M. nigricans spawning beds after 2015, and the last adult was captured in 2018. These results suggest that no breeding of largemouth bass occurred after 2018 and point to functional eradication with no further population growth in the lake. On the other hand, our environmental DNA analysis detected M. nigricans-specific DNA in all four surveys conducted between 2018 and 2022. Therefore, largemouth bass may still persist in or around Kanabara Dam Lake, although the estimated DNA concentrations were very low and we found no sign of increase after 2018. This suggests that, despite the apparent success of eradication efforts, the risk of reintroduction remains and ongoing monitoring is needed.

The Sakhalin taimen Parahucho perryi, one of the largest freshwater fish in Japan, is listed as Critically Endangered (CR) on the IUCN Red List. It occurs in rivers that contain marshes and wetlands with little land development. Therefore, floodplains are considered essential habitat for this species. However, most of our knowledge of Sakhalin taimen ecology concerns adults, and there is limited scientific knowledge of juveniles. In this study, we sought to identify the habitat characteristics of juvenile and adult Sakhalin taimen and compare them with those of sympatric fish species. The study took place in the Butokamabetsu River, which flows through the Uryu Experimental Forest of Hokkaido University and has a floodplain and well-developed anastomosing channels. Two areas were surveyed: the secondary side-channels, via electrofishing, and the main channel, via snorkelling. We also examined the physical environment of the study sites and the stomach contents of captured fishes. Thirty side-channel sites were surveyed, and all captured Sakhalin taimen were juveniles with fork lengths of 69–137 mm. Principal component analysis of the physical environment showed that juvenile Sakhalin taimen tended to be more abundant in lentic environments with low flow velocities and high turbidity. The stomachs of juvenile Sakhalin taimen contained fish, amphibians, and zooplankton (Cladocera), and a smaller proportion of terrestrial insects compared to the sympatric white-spotted charr Salvelinus leucomaenis and masu salmon Oncorhynchus masou. Twenty-one main-channel sites were surveyed, and all observed Sakhalin taimen were subadults or adults with fork lengths of 300–800 mm. Principal component analysis of the physical environment showed that subadult/adult Sakhalin taimen tended to be more abundant in deeper pools with more cover structure, such as woody debris. These results indicate that juvenile Sakhalin taimen select side channels with very slow currents, whereas subadult/adult Sakhalin taimen use deep pools in the main channel with sufficient cover. Conservation of floodplains and anastomosing channels is vital for the persistence of Sakhalin taimen in the wild.

We conducted a survey to determine the breeding status of the Japanese brown frog, Rana japonica, and observe its use of newly constructed spawning pools in Inzai City, Chiba Prefecture. The survey site, approximately 11 ha in area and located at the bottom of a valley, was mostly abandoned rice paddies. During the breeding seasons of 2021 and 2022, we recorded the number and location of egg masses from 29 sections within the overall site. Of more than 500 egg masses observed, more than half occurred in just two sections. In 2022, approximately 10% of the egg masses died, probably because of drying. More than 100 egg masses were laid in two pools constructed through citizen activities, with no eggs found in new rice paddies created near the pools. In habitats with dense spawning sites and often facing drought risks, constructing spawning pools may help reduce early mortality in R. japonica.