The expansion of invasive alien species (IASs) can negatively impact native ecosystems and human society. To effectively control IASs, it is important to understand their reproductive ecology. In Japan, Pallas’s squirrel is an IAS with potentially negative impacts on native fauna and flora via foraging, predation, and the spread of invasive parasites. Management strategies are urgently needed due to their population expansion in Kanagawa Prefecture. In this study, we used 333 adult female squirrel carcasses to investigate annual reproductive patterns including the effects of body size, body condition index, and age on reproductive conditions such as pregnancy, lactation, litter size, and placental scar numbers in breeding female Pallas’s squirrels. Of the 333 squirrels, 101 were pregnant and 73 were lactating. Only four females showed concurrent pregnancy and lactation. Although both pregnant and lactating females were observed throughout the year, pregnant females were observed most frequently in April, followed by August, indicating two distinct breeding peaks. There were higher proportions of lactating females between October and December than in all other months. The average litter size and number of placental scars were 2.08 and 1.26, respectively. We also found that younger female squirrels or those with a better body condition index were more likely to be pregnant. Lactation and placental scar numbers were positively correlated with body size, but not with the body condition index or age. None of the explanatory variables examined in this study influenced litter size. Together, our results indicate that Pallas’s squirrels in Kanagawa Prefecture reproduce year-round, which is consistent with populations in other regions, and that body condition and body size are important factors influencing reproductive output.

Green infrastructure (GI) is a conceptual framework for using ecosystems to support human social infrastructure. In recent years, there has been a growing trend to view urban green spaces as GI and examine the ecosystem services they provide. In this study, we quantitatively evaluated the potential air purification function of several tree species in urban green spaces based on their absorption of trace metal pollutants. From December 2022 to January 2023, we collected fallen leaves of four species (Quercus myrsinifolia Blume, Quercus serrata Murray, Acer palmatum Thunb., and Zelkova serrata (Thunb.) Makino) from the grounds of Tokyo Metropolitan University, Hachiōji, Tokyo, Japan. We used inductively coupled plasma atomic emission spectrometry (ICP-AES) to measure the abundance of four trace metals in fallen leaves: cadmium (Cd), copper (Cu), lead (Pb), and nickel (Ni). Quercus myrsinifolia, Q. serrata, and A. palmatum all absorbed pollutants (Z. serrata was excluded from analysis due to technical problems), but differed in the extent to which they absorbed each trace metal. Acer palmatum displayed high absorption of both Cd and Cu, but was uncommon in the study area. Quercus myrsinifolia displayed high absorption of Ni only; as an evergreen species, it could contribute air purification services year-round. In contrast, Q. serrata showed relatively limited trace metal absorption; however, as a deciduous species, its leaves can be readily collected and removed from the environment. The absorption characteristics of the three species are complementary and show promise as a component of comprehensive and effective GI.

The golden eagle (Aquila chrysaetos) is endangered in Japan due to declines in its population size and breeding success rate. To develop conservation measures, we conducted a nationwide evaluation of factors related to golden eagle breeding habitats. We compared thirty-six 1×1-km grids containing current or abandoned golden eagle nests nationwide based on avian expert knowledge and the literature. For quantitative analysis, we used a geographic information system to establish six habitat indices representing data on the feeding and nesting environments and human disturbance around the 36 grids. Then, we constructed generalised linear mixed models, setting breeding after 2010 (yes or no) as an objective variable, the six habitat indices as explanatory variables and geology as a random effect. The results show that current golden eagle breeding habitats were positively associated with larger natural deciduous broadleaf forest areas, higher terrain slopes and longer distances from main roads, and negatively correlated with forestry activity. Natural deciduous broadleaf forest and rugged topography were found to be particularly important for the continued breeding of golden eagles. Therefore, it is important to focus on conserving these landscape elements and to investigate measures to control human disturbances such as land development and breeding interference in these areas.

With the new global goal to achieve a recovery of biodiversity by 2030, the measurement and quantitative evaluation of biodiversity has become an important topic. In this study, we developed a method to evaluate the degree of habitat quality at a given site based on records of indicator species selected by focusing on the “nestedness” of the species assemblage. We used data from the Monitoring Site 1000 Satoyama Surveys conducted throughout Japan. In selecting indicator species, we verified that there is nestedness in the species composition, and then selected indicator species based on their frequency of occurrence throughout Japan. Candidates were selected based on criteria such as the strength of their relationship to the total number of species, their range of distribution, and the balance of ecosystem types. Finally, we selected 54 plant species, 37 bird species, and 22 butterfly species through expert judging by specialists from each taxon. The validation test using datasets from different study sites showed significant positive correlations between the number of indicator species and total number of species at each study site, as well as between the rarity index (expressed as the average of the inverse of its national frequency of occurrence of each indicator species) and the number of endangered species. However, the explanatory power of the selected indicator species to the total number of species and endangered species did not differ significantly from the average value when indicator species were selected randomly. Although these indicator species are not the best set for assessing biodiversity quantitatively, we were able to develop a method to assess the ecological status of each site, which can be used over a relatively large geographic range and ecosystem types, and with less effort and expertise than conventional methods that survey all species. This metric can also be used to identify important conservation areas within a region and to monitor protected areas and other effective area-based conservation measures (OECM), which will contribute to the realization of Nature Positive on a regional basis.

The Nagoya Daruma pond frog (Pelophylax porosus brevipodus) is native to paddy fields in Japan, where its population is declining with the modernisation of paddy field agriculture. To focus conservation efforts for this species, it is essential to acquire ecological information related to habitat selection. We investigated habitat preference at the landscape scale in the Hasu River Basin, Wakasa, Fukui Prefecture, Japan, for both P. p. brevipodus and a closely related species, the Black-spotted pond frog (Pelophylax nigromaculatus), to assess potential interspecies interactions. Distribution surveys for both species were conducted from June to July in 2022 and 2023. Using the maximum entropy (MaxEnt) model, we analysed relationships between frog distribution and potential environmental factors, including land use and topographic variables, to estimate suitable habitats for the two species. The results of our distribution survey indicated that P. p. brevipodus was mainly distributed in downstream areas of the Hasu River Basin, whereas P. nigromaculatus was broadly distributed throughout the basin. MaxEnt analysis revealed that mean elevation was the most critical environmental factor for habitat selection in P. p. brevipodus, suggesting a greater preference for downstream areas. In contrast, paddy area, the topographic wetness index, and distance to the nearest forest were the main environmental factors influencing habitat selection in P. nigromaculatus, leading to its relative scarcity in flat areas surrounding paddy fields. Therefore, we conclude that downstream paddy fields represent suitable conservation sites for P. p. brevipodus, as hybridisation is less likely in these areas.

Farming and other traditional land uses are being abandoned in mountainous rural communities throughout Japan. This study investigated factors influencing this trend and the effects of resulting landscape structural changes on species composition and function in four taxa in 20 rural communities of the village of Otari, at the foot of the Hakuba Mountains in Nagano Prefecture, Japan. The four taxa (birds, butterflies, ground-dwelling beetles, and plants) were selected for their different dispersal and resource dependence characteristics. Generalised linear model (GLM) analyses showed that the number of houses (as an index of workforce) and solar radiation amount (as an index of crop productivity) significantly influenced declines in farmland and landscape diversity from the 1950s to the present. Landscape structural changes significantly affected the species composition of the four taxa according to nonmetric multidimensional scaling ordination, as well as the numbers of individual migratory birds, univoltine butterflies, and specialist ground beetles according to GLM analysis. We conclude that the natural and socioeconomic factors controlling the persistence of rural communities played a significant role in altering the landscape structure in the study region, which in turn affected the species and functional composition of biological communities.

The habitats of freshwater mussels (family Unionidae) have become fragmented and scattered in agricultural ditches due to changes in land use. Pronodularia cf. japanensis 1 is found in only three geographically distant agricultural ditches in Ehime. Farmland consolidation is scheduled, and rehabilitation of agricultural ditches is planned. All mussels must be collected during this process, temporarily reared elsewhere under different conditions, and then released post-consolidation. This study developed a method to relocate P. japanensis temporarily during farmland consolidation. We conducted an experiment with marked P. japanensis individuals reared in five indoor experimental tanks and two cages suspended in two irrigation ponds. Additionally, some marked individuals were released back into the original agricultural ditch. The survival and growth of all marked individuals were tracked. The survival rate of P. japanensis in the experimental tanks was approximately 60% over 7 months, regardless of whether they were fed cultured diatoms, water from a plankton-rich agricultural ditch or stream, or a mix of commercially available diatoms, haptophytes, a chlorophyte, and Nannochloropsis. No shell growth was observed during the indoor-rearing period. In contrast, the survival rate in one irrigation pond was 82% over 33 months, with an approximate increase in shell length of 1 mm. Shell length increased by about 2 mm over the same period in the original agricultural ditch. Thus, the pond strategy is superior. This system will be used to temporarily relocate endangered freshwater mussels during farmland consolidation. After rehabilitating the ditches, relocated individuals will be released, and their survival and growth will be monitored.

Since the 1980s, population and distribution expansions of sika deer (Cervus nippon) in Japan have caused serious damage to agriculture, forestry and the natural environment. Deer population dynamics are affected by various factors including climate, food availability and hunting pressure, which vary regionally. Therefore, fundamental information describing local populations, such as age structure and fecundity, is important for developing appropriate management plans. We assessed the age structure, reproduction and body growth of 301 deer killed in the Mt. Asama region of Nagano Prefecture, Japan, where deer populations and distributions have expanded since the 2000s. The proportion of young females (aged 0–1 year) tended to increase over time, suggesting that juvenile survival may not decrease as population density increases. The study population appeared to maintain high pregnancy rates, with that of yearlings (50.8%) slightly lower than those of other local populations, whereas adult females (aged>2 years) had a higher pregnancy rate (91.0%). Growth curves based on body weight attained a plateau in females and males at 5 and 12 years of age, respectively, whereas those based on the total skull length, a body size indicator, plateaued in females and males at 3–4 and 7–8 years, respectively. Therefore, compared to other local populations, the deer population in the Mt. Asama region is expected to grow more slowly and take longer to reach maximum body weight and size. Because juvenile survival is not decreasing and adult females are maintaining high pregnancy rates, this deer population may still be expanding. However, recent population density increases may have delayed the age at first pregnancy and slowed growth in terms of body weight and size. Greater hunting pressure is needed to suppress deer population growth in the study region, and continuous monitoring of captured deer is essential to evaluate population dynamics.

In October 2020, an artificial reef was constructed in Wakasa Bay, around Ubejima Island off Sekumi Beach, Wakasa Town, Fukui Prefecture, Japan. Monitoring was conducted during three periods, immediately after construction and 2 and 3 years later. We surveyed seaweed species composition and coverage on the artificial reef, and on a natural reef as a control. At 2.5 years after artificial reef construction, spore bags containing the brown alga Sargassum patens were installed to increase seaweed coverage on the artificial reef. There was no change in seaweed species composition or vegetation coverage on the artificial reef before or after spore bag installation, with Sargassum macrocarpum remaining the dominant species, likely because deep-water areas such as our study site are suitable for S. macrocarpum growth, but not S. patens growth. Future spore bag installation projects must involve preliminary investigations of the environmental conditions and dominant species to ensure successful seaweed establishment.

The “Nature Symbiotic Sites” designated by the Ministry of the Environment, Japan, represent a Japanese policy tool under the framework of Other Effective Area-based Conservation Measures (OECMs), unintentionally contributing to biodiversity conservation. OECMs allow recognition of mechanisms that have historically supported biodiversity without deliberate intent. With the global target of designating 30% of both terrestrial and marine areas as protected areas or OECMs by 2030 (30 by 30), the identification and certification of lands influenced by mechanisms such as OECMs is essential for biodiversity conservation, sustainable use, and achieving the international 30 by 30 goal. This paper proposes that administrative boundaries, such as municipal or prefectural borders, act as social structures to unintentionally promote biodiversity conservation. The complexities of administrative procedures near these boundaries may lessen development pressures, indirectly supporting conservation. Case studies from Tokyo and Kanagawa Prefecture illustrate the biodiversity conservation approaches adopted by different municipalities. This paper addresses current challenges in biodiversity conservation within these regions and the potential contributions of Nature Symbiotic Sites. Finally, existing frameworks for cross-jurisdictional cooperation in applying for Nature Symbiotic Site status are evaluated, considering their feasibility.