Hyung-Kyu Nam

Colonial herons and egrets breed within highly heterogeneous landscapes where environmental conditions vary across multiple spatial scales. Although landscape structure is expected to shape colony-level species assemblages, explicit multi-scale empirical assessments remain scarce, particularly at national extents. We sought to (1) identify emergent species-assemblage types among heron and egret colonies across South Korea, (2) determine how these assemblages correspond to landscape heterogeneity across nested spatial scales, and (3) quantify the scale-dependent importance of environmental predictors influencing colony identity. We compiled species-specific nest counts from 176 breeding colonies and applied Self-Organizing Maps (SOM) to classify colony assemblages. Landscape variables were extracted from ESA CCI Plant Functional Type (PFT) datasets within five buffer radii: 500 m, 1 km, 3 km, 5 km, and 10 km. The relative importance of land-cover predictors at each spatial scale was evaluated using Random Forest models. SOM analysis revealed six ecologically distinct colony groups differing in species dominance, richness, and geographic distribution. Large-bodied species predominated in inland forested regions, whereas medium- and small-bodied species clustered in coastal and urban-rural mosaics. Environmental predictors showed scale-dependent patterns: built areas, managed herbaceous vegetation, and water-related cover dominated at fine scales; natural grasslands, bare land, and tree-related PFTs emerged at intermediate scales; and broader land-use variables remained important at 10 km. Colony assemblages arise from hierarchical interactions among fine-scale habitat features, river-corridor landscapes, and broader-scale land-use regimes. This hierarchical multi-scale perspective provides a landscape-ecological framework for anticipating how land-use change may alter the multi-scale landscape contexts supporting colonial wading birds.

Climate and land-use change are reshaping the spatial ecology of migratory waterbirds, yet few studies in East Asia have quantitatively integrated ensemble species distribution models, land-cover dynamics, and multi-scenario climate projections to assess future shifts and fragmentation of wintering habitats. We quantified climate-driven changes in the wintering distributions of six rice-paddy–dependent Anatidae species across South Korea using an ensemble species distribution modelling framework integrating nine algorithms. Species occurrence data from GBIF and field surveys (2022–2024) were combined with land-cover, topographic, and bioclimatic variables, with future projections generated under four Shared Socioeconomic Pathways (SSP126, SSP245, SSP370, SSP585) and four time periods (2021–2040, 2041–2060, 2061–2080, 2081–2100). Across all scenarios, wintering distributions exhibited pronounced northward shifts, reduced spatial overlap with historical hotspots, and increasing habitat fragmentation. The loss of southern wintering grounds—historically critical as climatic refugia during extreme cold events—combined with the rapid expansion of greenhouse-based agriculture threatens the stability of emerging northern habitats. While northward shifts may facilitate adaptation to gradual warming, they also heighten vulnerability to short-term climatic extremes, forcing energetically costly movements to suboptimal sites. These findings underscore the urgency of climate-informed conservation planning.

Climate change is a major factor contributing to the loss of habitat and decline of amphibian populations, posing a threat to biodiversity conservation. Bufonidae species are particularly sensitive to changes in their environment and vulnerable to climate change due to their strong homing instinct and frequent group behavior (mating and migration of juveniles). We identified the major distribution areas and habitat characteristics of two toad species found in Korea, toad, Bufo gargarizans, and water toad, B. stejnegeri, based on observation points and species distribution modeling. Distributional changes due to climate change were predicted. The toads used low altitudinal ranges and agricultural land, whereas the water toads used forested areas. The average model test area under the curve (AUC) value for toads was 0.695± 0.007, while the average test AUC value for water toads was 0.883±0.015. Toad distribution was most affected by temperature and altitude. By the 2100s, the number of occupied grid cells for toads and water toads is predicted to decrease by 99.57% and 100.00%, respectively, compared to the present number of occurred grid cells under the SSP 5-8.5 scenario. These critical data inform conservation measures for amphibians affected by global climate change.

Rice fields are important wildlife habitats; however, intensive agricultural practices have reduced the population of farmland birds. As a high-level consumer, the great egret (Ardea alba) serves as an indicator of the overall biodiversity of rice fields. However, little is known about the effects of farming methods on the feeding habitat selection of the great egret. Therefore, we examined the influence of eco-friendly and conventional farming methods on prey characteristics and great egret feeding behavior in rice field ecosystems. We employed focal observations and trap-based sampling to quantify prey characteristics and great egret feeding behaviors in eco-friendly and conventional rice fields. Great egrets showed more hunting attempts per minute and a higher intake rate in conventional fields, but feeding efficiency did not differ. Moreover, they consumed larger loaches in eco-friendly fields than in conventional fields. Great egrets exhibited slower feeding behaviors in eco-friendly fields due to the increased handling time of larger prey, such as loaches. Eco-friendly fields supported a higher abundance of larger-sized loaches than conventional fields, indicating their potential for supporting a higher abundance of great egrets. Our findings highlight the importance of sustainable farming practices for the conservation of the great egret.

The body condition of a snake species provides important physiological, morphological, and ecological information that elucidates its habits, life cycle, and competitive relationships. We measured the body size and condition of the wild Gloydius ussuriensis population in South Korea from 2018 to 2022, analyzed the degree of intraspecific niche overlap, and identified the geographic and climatic factors affecting their body condition. We found that the females were longer than the males. The body condition index (BCI) of G. ussuriensis differed depending on sex and season; the BCI of the females and males was highest in August and October, respectively. Environmental factors related to altitude and temperature affected the body condition of G. ussuriensis; BCI increased as the mean annual temperature and winter temperature increased; however, it increased when the annual temperature range decreased. The mean Pinaka index was 0.96, indicating a high degree of niche overlap; however, the niche overlap among the neonates was less than that among the adults and juveniles. To elucidate the causes of niche overlap and mechanisms behind the intraspecific competition among G. ussuriensis individuals, the habitat and utilization of food resources at different development stages of G. ussuriensis should be further investigated.

Intensification of cultivation methods and land‐use types, particularly in the face of climate change, has steadily weakened the habitat function of rice fields for waterbirds. Intermediate egrets (Ardea intermedia) are highly dependent on rice field habitats. Here, we examine the effect of a shift from rice monoculture to rice–barley double cultivation on the use of rice fields by intermediate egrets in South Korea. Rice–barley double cultivation has been increasing steadily in the southern region of South Korea due to changes in the rice growth period under climate change and maximization of economic benefits. We studied rice fields to determine the effect of the rice–barley double cultivation area on the abundance of intermediate egrets on the regional scale and their potential distribution pattern in response to double cultivation in relation to climate change using national‐scale climate, altitude and land cover data from 1 May to 23 June 2018. Compared to the irrigation practices used for rice monoculture, irrigation was stopped for some time in rice–barley double cultivation prior to planting, compromising the role of rice fields as a food ground for intermediate egrets. The potential abundance of intermediate egrets rapidly decreased by half when the double cultivation area increased to >40% of the total rice‐field area, and was less than one individual if the area increased to >80%. Furthermore, according to climate change projections, by 2100, the double cultivation area would account for 75.74% of the predicted range of intermediate egret foraging ground. Synthesis and applications. Double cultivation areas should be <40% of existing rice fields to minimize the impact of the change in cultivation practices. This approach can also convert rice fields to other types of land use. Consequently, appropriate conservation and management measures may be developed to maintain suitable habitats despite rapidly changing cultivation practices resulting from climate change.

The body condition of a snake species provides important physiological, morphological, and ecological information that elucidates its habits, life cycle, and competitive relationships. We measured the body size and condition of the wild Gloydius ussuriensis population in South Korea from 2018 to 2022, analyzed the degree of intraspecific niche overlap, and identified the geographic and climatic factors affecting their body condition. We found that the females were longer than the males. The body condition index (BCI) of G. ussuriensis differed depending on sex and season; the BCI of the females and males was highest in August and October, respectively. Environmental factors related to altitude and temperature affected the body condition of G. ussuriensis; BCI increased as the mean annual temperature and winter temperature increased; however, it increased when the annual temperature range decreased. The mean Pinaka index was 0.96, indicating a high degree of niche overlap; however, the niche overlap among the neonates was less than that among the adults and juveniles. To elucidate the causes of niche overlap and mechanisms behind the intraspecific competition among G. ussuriensis individuals, the habitat and utilization of food resources at different development stages of G. ussuriensis should be further investigated.