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Wildlife monitoring is carried out for diverse reasons, and monitoring methods have gradually advanced through technological development. Direct field investigations have been replaced by remote monitoring methods, and unmanned aerial vehicles (UAVs) have recently become the most important tool for wildlife monitoring. Many previous studies on detecting wild animals have used RGB images acquired from UAVs, with most of the analyses depending on machine learning–deep learning (ML–DL) methods. These methods provide relatively accurate results, and when thermal sensors are used as a supplement, even more accurate detection results can be obtained through complementation with RGB images. However, because most previous analyses were based on ML–DL methods, a lot of time was required to generate training data and train detection models. This drawback makes ML–DL methods unsuitable for real-time detection in the field. To compensate for the disadvantages of the previous methods, this paper proposes a real-time animal detection method that generates a total of six applicable input images depending on the context and uses them for detection. The proposed method is based on the Sobel edge algorithm, which is simple but can detect edges quickly based on change values. The method can detect animals in a single image without training data. The fastest detection time per image was 0.033 s, and all frames of a thermal video could be analyzed. Furthermore, because of the synchronization of the properties of the thermal and RGB images, the performance of the method was above average in comparison with previous studies. With target images acquired at heights below 100 m, the maximum detection precision and detection recall of the most accurate input image were 0.804 and 0.699, respectively. However, the low resolution of the thermal sensor and its shooting height limitation were hindrances to wildlife detection. The aim of future research will be to develop a detection method that can improve these shortcomings.
SeungHyeon Lee; YoungKeun Song; Sung-Ho Kil. Feasibility Analyses of Real-Time Detection of Wildlife Using UAV-Derived Thermal and RGB Images. Remote Sensing 2021, 13, 2169 .
AMA StyleSeungHyeon Lee, YoungKeun Song, Sung-Ho Kil. Feasibility Analyses of Real-Time Detection of Wildlife Using UAV-Derived Thermal and RGB Images. Remote Sensing. 2021; 13 (11):2169.
Chicago/Turabian StyleSeungHyeon Lee; YoungKeun Song; Sung-Ho Kil. 2021. "Feasibility Analyses of Real-Time Detection of Wildlife Using UAV-Derived Thermal and RGB Images." Remote Sensing 13, no. 11: 2169.
Although many studies have considered urban structure when investigating urban ecological networks, few have considered the three-dimensional (3D) structure of buildings as well as urban green spaces. Airborne LiDAR datasets provide an opportunity to quantify 3D structure and evaluate 3D metrics in connectivity mapping. We examined an urban ecological network using the 3D structure of both green spaces and buildings. Using breeding-season bird species observations and airborne LiDAR data collected, we assessed the influence of 3D structural variables on species diversity. We used correlation analyses to determine if vertical distribution, volume, area, and height of both buildings and vegetation were related to bird species diversity. Then we conducted circuit theory-based current flow betweenness centrality (CFBC) analysis using the LiDAR-derived structural variables. We found that the volumes of buildings and 8–10 m vegetation heights were both highly correlated with species richness per unit area. There were significant differences between 2D and 3D connectivity analysis using LiDAR-derived variables among urban forest patches, boulevards, and apartment complexes. Within urban forest patches and parks, 3D CFBC represented canopy structural characteristics well, by showing high variance in spatial distributions. The 3D CFBC results indicated that adjacent high-rise buildings, dense apartment complexes, and densely urbanized areas were isolated, as characterized by low centrality values, but that vegetation planted in open spaces between buildings could improve connectivity by linking isolated areas to core areas. Our research highlights the importance of considering 3D structure in planning and managing urban ecological connectivity.
Heejoon Choi; YoungKeun Song; Wanmo Kang; James H. Thorne; Wonkyong Song; Dong Kun Lee. LiDAR-derived three-dimensional ecological connectivity mapping for urban bird species. Landscape Ecology 2021, 36, 581 -599.
AMA StyleHeejoon Choi, YoungKeun Song, Wanmo Kang, James H. Thorne, Wonkyong Song, Dong Kun Lee. LiDAR-derived three-dimensional ecological connectivity mapping for urban bird species. Landscape Ecology. 2021; 36 (2):581-599.
Chicago/Turabian StyleHeejoon Choi; YoungKeun Song; Wanmo Kang; James H. Thorne; Wonkyong Song; Dong Kun Lee. 2021. "LiDAR-derived three-dimensional ecological connectivity mapping for urban bird species." Landscape Ecology 36, no. 2: 581-599.
Anthropogenic land use has led to the loss and fragmentation of native habitats and disruption to ecosystem processes, resulting in a decline in landscape connectivity and biodiversity. Here, in order to find the potentials of improvements in ecological connectivity, we provide a spatial analysis to present differences in ecological connectivity based on land cover maps and urban habitat maps in Suwon city, Republic of Korea. We generated two permeability maps for use in a network analysis, one being land cover and the other urban habitat, including a 5-km buffer area from the city boundary. We then determined the current-flow betweenness centrality (CFBC) for each map. Our results indicate that forests are typically the most highly connected areas in both maps. However, in the land cover map results, nearly all high-priority areas were in the mountainous region (CFBC value: 0.0100 ± 0.0028), but the urban habitat indicated that grasslands and rivers within the city also significantly contribute to connectivity (CFBC value: 0.0071 ± 0.0022). The CFBC maps developed here could be used as a reference when introducing green infrastructure in cities. Before establishing ecological networks for urban areas, future work should integrate the land use and ecological data of different administrative districts with continuous ecological connection.
Dohee Kim; Wonhyeop Shin; Heejoon Choi; Jihwan Kim; YoungKeun Song. Estimation of Ecological Connectivity in a City Based on Land Cover and Urban Habitat Maps. Sustainability 2020, 12, 9529 .
AMA StyleDohee Kim, Wonhyeop Shin, Heejoon Choi, Jihwan Kim, YoungKeun Song. Estimation of Ecological Connectivity in a City Based on Land Cover and Urban Habitat Maps. Sustainability. 2020; 12 (22):9529.
Chicago/Turabian StyleDohee Kim; Wonhyeop Shin; Heejoon Choi; Jihwan Kim; YoungKeun Song. 2020. "Estimation of Ecological Connectivity in a City Based on Land Cover and Urban Habitat Maps." Sustainability 12, no. 22: 9529.
Reduced vegetation growth ultimately induces degradation of the ecosystem and CO2 sequestration. Multiple risks can affect vegetation, but climate change and human influence have been particularly known to be major risks for deteriorating the ecosystem. However, there is limited information illustrating comprehensive impact pathways that consider both climatic and human impacts on vegetation. To promote optimum decision-making, information is required to elucidate complex cause-and-effect pathways in order to determine how various impacts are related and which ones are more important. Hence, we identified impact pathways affecting enhanced vegetation index (EVI) regarding climate and human factors by revealing a causal network using the Bayesian network approach. Vulnerable vegetation types and the spatial range of impact were evaluated based on the identified network by analyzing temporal changes in annual average EVI, human-induced land conversion, and multiple climate extremes from 2002 to 2014 on Jeju Island, South Korea. The results indicated the high vulnerability of coniferous forests compared with mixed and deciduous forests were able to elucidate the major impact paths, including human-induced land conversion at lower elevation, length of frost, degree of heat, and general intensity of wetness (Pearson’s r = 0.58). Existing policies in the study site have been insufficient to avoid the major paths influencing vegetation state. This study offers insights into comprehensive impact paths in order to support effective decision-making for nature conservation.
Yoon Jung Kim; Young Keun Song; Dong Kun Lee; Kim; Song; Lee. Understanding the Critical Impact Path on Vegetation Growth under Climate Extremes and Human Influence. Forests 2019, 10, 947 .
AMA StyleYoon Jung Kim, Young Keun Song, Dong Kun Lee, Kim, Song, Lee. Understanding the Critical Impact Path on Vegetation Growth under Climate Extremes and Human Influence. Forests. 2019; 10 (11):947.
Chicago/Turabian StyleYoon Jung Kim; Young Keun Song; Dong Kun Lee; Kim; Song; Lee. 2019. "Understanding the Critical Impact Path on Vegetation Growth under Climate Extremes and Human Influence." Forests 10, no. 11: 947.
Understanding forest dynamics is important for assessing the health of urban forests, which experience various disturbances, both natural (e.g., treefall events) and artificial (e.g., making space for agricultural fields). Therefore, quantifying three-dimensional changes in canopies is a helpful way to manage and understand urban forests better. Multitemporal airborne light detection and ranging (LiDAR) datasets enable us to quantify the vertical and lateral growth of trees across a landscape scale. The goal of this study is to assess the annual changes in the 3-D structures of canopies and forest gaps in an urban forest using annual airborne LiDAR datasets for 2012–2015. The canopies were classified as high canopies and low canopies by a 5 m height threshold. Then, we generated pixel- and plot-level canopy height models and conducted change detection annually. The vertical growth rates and leaf area index showed consistent values year by year in both canopies, while the spatial distributions of the canopy and leaf area profile (e.g., leaf area density) showed inconsistent changes each year in both canopies. In total, high canopies expanded their foliage from 12 m height, while forest gap edge canopies (including low canopies) expanded their canopies from 5 m height. Annual change detection with LiDAR datasets might inform about both steady growth rates and different characteristics in the changes of vertical canopy structures for both high and low canopies in urban forests.
Heejoon Choi; YoungKeun Song; Youngwoon Jang. Urban Forest Growth and Gap Dynamics Detected by Yearly Repeated Airborne Light Detection and Ranging (LiDAR): A Case Study of Cheonan, South Korea. Remote Sensing 2019, 11, 1551 .
AMA StyleHeejoon Choi, YoungKeun Song, Youngwoon Jang. Urban Forest Growth and Gap Dynamics Detected by Yearly Repeated Airborne Light Detection and Ranging (LiDAR): A Case Study of Cheonan, South Korea. Remote Sensing. 2019; 11 (13):1551.
Chicago/Turabian StyleHeejoon Choi; YoungKeun Song; Youngwoon Jang. 2019. "Urban Forest Growth and Gap Dynamics Detected by Yearly Repeated Airborne Light Detection and Ranging (LiDAR): A Case Study of Cheonan, South Korea." Remote Sensing 11, no. 13: 1551.
Dong Kun Lee; YoungKeun Song. Special issue: Urban green infrastructure and the ecological functions. Landscape and Ecological Engineering 2019, 15, 241 -243.
AMA StyleDong Kun Lee, YoungKeun Song. Special issue: Urban green infrastructure and the ecological functions. Landscape and Ecological Engineering. 2019; 15 (3):241-243.
Chicago/Turabian StyleDong Kun Lee; YoungKeun Song. 2019. "Special issue: Urban green infrastructure and the ecological functions." Landscape and Ecological Engineering 15, no. 3: 241-243.
The spread of invasive plants in urban forests is of great concern to land managers and ecologists. Here, we analyse the distribution pattern and potential occurrence of a problematic invasive plant, Ageratina altissima, on Mt. Umyeon, in the Seoul metropolitan area of South Korea, using multiple species distribution modelling with geographic information system layers and a time series of Landsat 8 satellite imagery data. Also, we identify this species’ potential dispersal corridors using a network-based landscape lattice approach. All five species distribution models performed well with a range of test area under the receiver operating characteristic curve values of 0.843–0.899 with an average of 0.876. Distance from trails had the greatest effect on its occurrence probability, and generally exerted a negative influence within ca. 20 m of trails, indicating that urban forest trails facilitate the spread of invasive plants. Of the remote sensing-based predictors used, 7 August 2016 tasselled cap brightness index was an important variable having a negative effect on the presence of A. altissima. Elevation generally had a positive effect on its presence, although it was less important than tasselled cap brightness index. We explicitly detected the distribution pattern of high invasion risk corridors, mostly located on or around trails, which follow the central ridgeline of the study area. The results and approaches employed here can be useful for understanding, monitoring, and predicting invasive plant distribution and spread for the management of urban natural resources and biodiversity conservation.
Wanmo Kang; YoungKeun Song; Dongkun Lee; Gowoon Kim; Heemyung Chae. Identifying habitats and corridors of an invasive plant, Ageratina altissima, in an urban forest. Landscape and Ecological Engineering 2019, 15, 277 -287.
AMA StyleWanmo Kang, YoungKeun Song, Dongkun Lee, Gowoon Kim, Heemyung Chae. Identifying habitats and corridors of an invasive plant, Ageratina altissima, in an urban forest. Landscape and Ecological Engineering. 2019; 15 (3):277-287.
Chicago/Turabian StyleWanmo Kang; YoungKeun Song; Dongkun Lee; Gowoon Kim; Heemyung Chae. 2019. "Identifying habitats and corridors of an invasive plant, Ageratina altissima, in an urban forest." Landscape and Ecological Engineering 15, no. 3: 277-287.
Human-induced land degradation fragments natural ecosystems, hinders ecological processes, and threatens biodiversity. Maintaining or restoring ecological flows across landscapes through landscape linkages may provide a solution. Here, we identify a peninsula-wide ecological connectivity network for the Korean Peninsula using two linkage mapping models. We found three major north-south axes of connectivity traversing the Demilitarized Zone (DMZ), which emerged as an important east-west linkage. Only 7% of the highest-ranked connections are currently secured by protected areas. We found 120 linkages in North and South Korea that are intersected by road networks consisting of motorways and trunk roads under both models. These locations should be the focus of immediate attention for conservation planners, as well as 274 and 1130 additional road-impacted linkages under one model or the other. The results can be used for policy support, and potentially as a basis for the two countries to engage in discussions about ecosystem health and climate change adaptation. The approach presented here can also be efficiently used to assess and map natural landscape linkages.
Wanmo Kang; James H. Thorne; Gowoon Kim; Dongkun Lee; YoungKeun Song. Conserving terrestrial linkages that connect natural landscapes of the Korean Peninsula. Environmental Monitoring and Assessment 2019, 191, 385 .
AMA StyleWanmo Kang, James H. Thorne, Gowoon Kim, Dongkun Lee, YoungKeun Song. Conserving terrestrial linkages that connect natural landscapes of the Korean Peninsula. Environmental Monitoring and Assessment. 2019; 191 (6):385.
Chicago/Turabian StyleWanmo Kang; James H. Thorne; Gowoon Kim; Dongkun Lee; YoungKeun Song. 2019. "Conserving terrestrial linkages that connect natural landscapes of the Korean Peninsula." Environmental Monitoring and Assessment 191, no. 6: 385.
In many metropolitan areas, the urban fringe is defined by highly sensitive habitats such as forests and wetlands. However, the explosive growth of urban areas has led to the formation of informal settlements in the urban fringe, subsequently threatening these sensitive habitats and exaggerating several social and environmental problems. We seek to improve the current understanding of informal settlements and their formation in the metropolitan fringe through a comprehensive spatiotemporal analysis of the Guryong Area (GA) in the Gangnam District, Seoul, South Korea. We measured the land-use and land-cover (LULC) changes in the entire GA from 1950 to 2015, and then analyzed the changes in one specific land-use type defined as “spontaneous settlements”. We then combined these changes with landform and slope data in 600-m-wide bands along the gradient of urbanization. The results showed spontaneous settlements distributed in small clusters in 1975, and the growth of this distribution into larger, more condensed clusters beginning in 1985. Between 1950 and 2015, the total area of spontaneous settlements decreased, while the settlement locations shifted from the urban core to the marginal area of the GA. Meanwhile, the locations selected for spontaneous settlements moved from plain areas with slopes of 2–7%, to more steeply sloped, remote areas such as the mountain foothills with slopes of 15–30%. These results suggest that the spatial characteristics of informal settlements are shown in the degree of aggregation and marginalized trend indicated from the analysis of spontaneous settlements. Finally, we hope the spatial analysis can be used as a basis and starting point for the evaluation process of informal settlement redevelopments in other areas of Seoul, as well as in other Asian cities.
Yiwen Han; YoungKeun Song; Lindsay Burnette; David Lammers. Spatiotemporal Analysis of the Formation of Informal Settlements in a Metropolitan Fringe: Seoul (1950–2015). Sustainability 2017, 9, 1190 .
AMA StyleYiwen Han, YoungKeun Song, Lindsay Burnette, David Lammers. Spatiotemporal Analysis of the Formation of Informal Settlements in a Metropolitan Fringe: Seoul (1950–2015). Sustainability. 2017; 9 (7):1190.
Chicago/Turabian StyleYiwen Han; YoungKeun Song; Lindsay Burnette; David Lammers. 2017. "Spatiotemporal Analysis of the Formation of Informal Settlements in a Metropolitan Fringe: Seoul (1950–2015)." Sustainability 9, no. 7: 1190.