Abandoned houses are increasing as people leave them behind. The problem of vacant houses has emerged as a national issue. It does not discriminate based on size or location, from major cities like Busan to islands like Ulleungdo. The situation is serious in small cities and rural areas with a population of less than 300,000, which are experiencing population decline. When vacant houses increase, problems arise such as garbage being discarded or heightened risks of crime. Villages disappear, and public services like safety, health, and transportation are eventually at risk of being discontinued.
The government is encouraging the demolition of abandoned houses in cities and rural areas by reforming laws in 2023. Most places where houses once stood remain vacant lots. This phenomenon, referred to as "urban perforation," is described as resembling a city with holes, and some scholars liken it to osteoporosis in cities, as if bones have holes formed by calcium depletion. The government and local governments are considering ways to utilize the land after demolishing these houses. However, there is currently no data available on the status of urban perforation needed to formulate policies.
Building area 1.5 times larger than Bonghwa soccer field has disappeared in 7 years
The satellite service company Naraspace has announced the results of an analysis of urban perforation phenomena in Bonghwa County, a region with a high proportion of underpopulated areas in North Gyeongsang Province, and medium-sized cities such as Sangju, Gimcheon, and Namwon in Jeonbuk, using aerial photographs and satellite images in collaboration with Professor Park Yoon-mi of the Department of Civil and Environmental Engineering at Seoul National University and Research Institute An Ji-hyun.
Underpopulated areas are regions where the population has decreased to a point where it is difficult to sustain reproduction due to an aging resident population or increased migration to other areas. According to the National Geographic Information Institute, among 250 cities and counties nationwide, over 35% of 50 areas classified as small cities are underpopulated. In contrast, the metropolitan area of Seoul has a 3.84% rate, and the greater Seoul area, including Gyeonggi and Incheon, has a 10.10% rate. Bonghwa has the highest percentage of underpopulated areas among municipalities nationwide, at 49.81%.
The research team analyzed the changes that occurred in Bonghwa, Gyeongsangbuk-do, utilizing deep learning-based Change Detection technology. Change detection is a video analysis technique that detects changes in the same area taken at regular time intervals.
The research team examined the urban perforation phenomenon in Bonghwa County by dividing it into three districts and using aerial images from 2015 and 2022 provided by the National Geographic Information Institute. They focused primarily on detecting locations where buildings had disappeared and turned into vacant lots. The analysis revealed that a building near the Young Poong Smelting Company in Seokpo-myeon, Bonghwa County, which existed in 2015, had disappeared and turned into a vacant lot by 2022. The smelting company has operated in Seokpo-myeon, Bonghwa County, since 1970 and is the world's fourth-largest zinc producer. During the same period, some buildings near the Seokpo Health Center and the entrance of Seokpo 3-ri north of Seokpo Station also disappeared and were confirmed to have changed into vacant lots.
The research team found that there were a total of 16 instances of urban perforation in Bonghwa County during this period, covering an area of 11,400 square meters. This is equivalent to 1.5 times the size of a soccer field, or the average area of 162 households when calculated based on the average dwelling size in Korea (21 pyeong, 70.1 square meters).
Holes appear throughout Sangju, Gimcheon, and Namwon
Change detection technology is used in various fields, but in urban areas, it is employed to capture newly appearing large and small perforations. Professor Park noted, "Identifying urban perforation phenomena on a large scale will significantly contribute to preemptively understanding various problems arising in the city and formulating countermeasures."
The research team also examined the perforation phenomena appearing in Sangju, Gimcheon, and Namwon in Jeonbuk, which are experiencing population decline. These cities have also seen a continued outflow of population recently, weakening urban functionality.
The population of Sangju city first fell below 100,000 in 2017, decreasing by 1,000 each year. Analyzing aerial photos of Sangju taken in 2013 and 2023 revealed that urban perforation has not yet occurred extensively in this area. During this period, buildings located to the west and east of the Sambaek Sauna in Seoseong-dong of Sangju disappeared and were confirmed to have turned into a parking lot and grass field, respectively. Similarly, buildings on the east and west sides of the Sangju Post Office were also found to have disappeared and been transformed into vacant lots. According to the street view provided by Naver, these spaces have now been confirmed as urban parking lots.
It has been revealed that from 2013 to 2023, large buildings in Gimcheon, Gyeongbuk, and Namwon, Jeonbuk, have gradually disappeared. As the population decreases, most demolition sites are left as vacant land with no new buildings being constructed. The analysis indicates that even in these regions, areas remaining after building demolitions become vacant lots or vacant land where shrubs grow.
According to the Korea Real Estate Board, there were 134,082 vacant houses nationwide last year. The houses most often demolished are those that have become uninhabitable due to age. In Sangju alone, the percentage of old houses over 30 years old reaches 64.9%. When visiting small cities, one can see numerous vacant lots where old houses have been demolished between old city buildings. Sometimes, there are only weeds growing, and at other times, they are utilized as parking space.
Urban holes impact environmental and health issues and local climate
Globally, the issues of population decline and vacant houses are emerging as common problems. Whether in urban or suburban areas, perforation is not uniform and appears randomly.
Indiscriminate demolition of vacant houses and the resulting abandoned lots harm urban aesthetics and become breeding grounds for illegal parking and illegal dumping of waste. This may even lead to soil pollution and water quality contamination of rivers. Urban perforation is also affecting city climates. Last year, researchers from Pusan National University and Kyungsung University released findings in the international journal Environment and Planning B indicating that the urban climate environment (local climate) changes based on the characteristics of lots created after the demolition of long-abandoned vacant houses. When vacant houses are demolished and the land is paved with concrete, the heat environment index is consistently higher compared to when trees are planted and the area is converted into green space. Researchers indicated that if vacant lots created by the demolition of vacant houses are covered with concrete, it may actually adversely affect the urban heat island effect and precipitation patterns. Professor Park stated, "Strategically demolishing vacant houses will increase urban ventilation and enhance thermal comfort by creating wind paths." He also noted that most vacant lots are still private property, and thus, local government intervention is limited, while owners cannot manage them well.
Japan has amended related laws to respond to "urban spongification." Urban spongification refers to the phenomenon where vacant houses and lots appear randomly in cities due to population decline. Likewise, in Detroit, Michigan, the population has decreased and vacant houses have increased due to the decline of the automobile industry.
South Korea is no exception. The risk of extinction areas in South Korea has been increasing since the first survey results were announced in 2016. According to future population projections released by the National Statistical Office, the population in the metropolitan area is expected to decrease by 5.3% from 2022 to 2052, while the Yeongnam region is expected to decrease by 22.5% and the Honam region by 16.3%. In rural small cities with serious aging, more vacant houses and urban perforation phenomena are anticipated.
The government is implementing measures to overcome the local extinction crisis caused by population decline. In South Korea, the "Urban Vacant House Management Project" is being promoted in 2023, revising laws and providing guidelines to promote the utilization of land after demolishing vacant houses. However, statistics or current data related to urban perforation phenomena are still woefully insufficient.
Utilizing satellite imagery for detecting vacant houses in extensive areas
Research on vacant houses and urban perforation is most active in Japan. Japan is also experiencing a rapid decline in rural populations. Researchers from the University of Tokyo and Chiba University are analyzing the patterns of perforation occurring in Chiba Prefecture, where the population is rapidly declining.
In the United States, patterns of vacant houses arising in old urban areas, like Baltimore and Chicago, are being confirmed to develop predictive models for future vacancies. In South Korea, a study conducted in 2023 by Professor Hong Seong-jo of Chungbuk National University analyzed 19 small cities experiencing population decline and revealed a correlation between the proportion of elderly population, buildings over 35 years old, and increasing vacancies, as well as the farther they are from areas where the population is increasing. Professor Park's research team, in collaboration with researchers from Texas A&M University in 2021, analyzed 141 cities in South Korea and found that factors like aging, the decline of manufacturing jobs, and increases in new housing tax have influenced the rise in vacant houses.
Recently, methods for analyzing extensive areas utilizing aerial imagery, satellite imagery, and street view images have also been developed. Researchers at the State University of New York at Buffalo utilized high-resolution aerial images in 2021 to detect vacant houses. They identified houses that appeared in images in 2011 but disappeared by 2014 as a basis for detecting vacancies. Researchers from Tsinghua University in China reported in the international journal Landscape and Urban Planning in 2022 that they have successfully identified nearly 90% of lots created in 36 cities in China using Google satellite images. According to Naraspace, signs like untended trees around a house, garbage outside, or a damaged roof are indicators for determining vacant house status. In the U.S., vacant houses are identified based on missing roofs or doors boarded up with wood.
This analysis utilized aerial images and satellite imaging. Aerial photographs have limitations in detecting changes occurring quickly due to their long capture intervals for the same area. High-resolution satellite imagery is necessary to analyze urban perforation phenomena in small cities. While satellite imagery has become more frequent due to the increase in private satellite corporations, its high cost remains a significant limitation.
Professor Park noted, "If we continuously observe using remote sensing technologies such as aerial and satellite images, we will likely be able to respond promptly to urban safety, health, and environmental issues."
[Interview] "The rapidly increasing issue of vacant houses in local cities and urban perforation; quick status identification is a task at hand"
Professor Park Yoon-mi, Seoul National University
"Korean society is facing social issues such as population decline and aging that lead to local extinction. The situation is particularly serious in small cities with populations under 300,000."
Professor Park Yoon-mi from the Department of Civil and Environmental Engineering at Seoul National University pointed out that as the population declines nationwide, the number of vacant houses is increasing, leading to a rapid expansion of vacant lots in cities—a phenomenon referred to as urban perforation. Furthermore, she emphasized that current information and statistics are critically lacking. Professor Park is researching solutions to the problems future cities will face by utilizing smart technologies and cloud control. The increasing phenomenon of vacant houses in local cities is one of the major concerns. She and her research team are searching for fundamental countermeasures and solutions to the problem of vacant houses increasing and being left as vacant lots after demolition.
Similar phenomena are occurring in the United States, Europe, and Japan, but solutions remain elusive. Professor Park believes that deeply understanding vacant houses and urban perforation phenomena may provide clues to solving the extinction problem in small cities. She emphasized, "The issue of vacant houses directly relates to the quality of life, necessitating the active collection of more data and the establishment of countermeasures." Professor Park, who analyzed the situation in Bonghwa, Sangju, and Gimcheon using aerial and satellite photos, was interviewed along with Research Institute An Ji-hyun, who participated in the analysis.
- How are vacant houses being utilized?
"When vacant houses are demolished, the space is primarily used as parking lots or vegetable gardens. The same is true for areas like Bonghwa and Sangju that were investigated. Various local governments express interest in using these spaces as vegetable gardens. In some rural cities, they are also often utilized as practical social overhead capital (SOC) such as parking lots. Cities like Jeongeup and Andong frequently express intentions to develop public parking lots after demolishing vacant houses. However, currently, there are no sharp solutions beyond these options."
- Isn't it better to leave it as a vacant lot rather than abandon it?
"That's true. Vacant houses can become hotspots for crime and litter, posing environmental and health challenges. However, when holes appear in the urban area, people may roam around and unintentionally cause problems that weren't previously considered. This can lead to an increase in ground temperature. They can also become habitats for wild animals if not maintained properly."
- How are the government and local governments responding to the issue of vacant houses?
"As the number of vacant houses continues to grow, it has become a situation where the government cannot help but intervene. Currently, demolition is the only solution to the vacant house problem in South Korea. In 2023, the government amended the 'Special Act on the Management of Vacant and Small Houses' and the 'Rural Redevelopment Law' to encourage the demolition of abandoned houses. By April 2024, the results of a nationwide survey on vacant houses will also be disclosed. The government is managing vacant houses by grading them."
- Is the status of urban perforation being accurately assessed?
"The status assessments are not being carried out effectively. The current process takes too long to investigate vacant houses. There is a hassle of needing to send people directly. Even if someone wants to demolish a vacant house, the situation data is not updated quickly enough, leading to delays in applying for government benefits. The situation remains similar even after the vacant houses are demolished, as there is no data showing how they are being used after demolition. It is essential to quickly survey many areas and continuously update the status to confirm the context of the situation as 'phenomena.'"
- What patterns are evident in South Korea?
"In regions experiencing population decline, a phenomenon occurs where residential density decreases, akin to calcium depletion in bones. As research progresses, it’s crucial to observe whether urban perforation occurs more frequently on the outskirts or in city centers. Even if vacancies arise, patterns may differ by region due to varying available resources. The pattern of urban perforation resembles the types of vacant houses that appear. Naturally, a decrease in population density leads to an increase in vacant houses. The factors directly inducing urban perforation phenomena have not yet been identified. However, there is a high likelihood that urban perforation occurs in areas with a high proportion of elderly residents or declining industries due to reduced housing demand."
- Why is urban perforation in small cities or rural areas a focus?
"In many small cities in South Korea, the population is declining due to the deaths of elderly residents or increases in out-migration. These regions often lack capacity or resources. Compared to major cities such as Seoul and Busan, where policies can be more effectively structured, small cities do not have the same level of planning. Therefore, preparations for these cities are essential."
- If holes appear throughout the city, it seems that public services like transportation, safety, and health would also collapse.
"When vacant houses increase in a region, there are methods to either wait until what little housing remains is occupied or encourage residents to move to more livable areas. In Japan, there was a project known as 'location optimization' which assisted migration, but it wasn't very successful. This is because leaving a place where one has lived all their life is not easy, and often homes and workplaces are closely linked. However, to maintain quality of life, it is necessary to determine which public services need to be maintained until when, and where to begin anew. An accurate diagnosis of reality is the most crucial first step."
- Is the vacant house problem serious abroad as well?
"Japan, like South Korea, is facing serious population extinction crises in its small cities. The United States has also been actively managing these issues. While they don’t use the term 'urban perforation', they refer to it as 'vacant lots'. In Europe, the terms 'demolition' or others are used. Besides problems arising from economic stagnation or job losses, there were cases where East Germans migrated to West Germany after unification, leaving vacant houses in East Germany. Population decline usually becomes evident first through vacant houses. This is a concern in most cases of population decline. Cities or countries with stagnant or declining industries are all worried about this issue."
- How are vacancies being addressed abroad?
"In the United States, vacant houses may be sold for $1,000, while in Chicago, they can be sold for $100 or $250. However, the easiest way to manage vacant houses is through demolition. In the U.S., only about 1-2% of vacant houses become urban gardens or are recycled, while most are abandoned. Detroit, a representative city in the Rust Belt, primarily manages vacant houses by demolishing them. While it would be nice to reuse them, areas where residents have departed often lack demand, making management challenging. In contrast, in the UK, some elderly residents grow vegetables or flowers in those spaces."
- How should urban perforation be utilized from a long-term perspective?
"Currently, there are no exemplary cases. More data collection and analysis is required. An example from a 2017 report by Philadelphia's land banking indicated that priorities for development should be based on whether perforation is dispersed or concentrated. While some suggest returning areas to nature, this is difficult when houses still remain. It would require a more extensive area to be feasible. There is an example in the U.S. known as Buffalo Commons. Originally the land of buffalo in the central plains of the U.S., it was inhabited by humans for a time. Now that the population density has decreased, areas of the land are becoming uninhabited. Frank Popper, a professor at Rutgers University, has advocated for returning unused areas to buffalo as much as possible.
- How can urban perforation measures be improved?
"The assessment of the vacant house situation is conducted once every five years, yet the speed at which vacant houses arise is much faster. We need methods to detect vacancies quickly and analyze how they are used or what forms they take post-demolition. This is necessary to decide what kind of facilities to introduce or what needs to be restored in future policies."
References
Naraspace Earth Paper, https://ep.naraspace.com/
With the development of low-cost space launch vehicles and small satellite technologies, we have entered an era where events on Earth can be monitored in real-time. Satellites are now used not only for defense but also for disaster monitoring, damage assessment, and industrial trend analysis across various domains. ChosunBiz is publishing a series on space journalism called ‘The World Seen from Satellites’ and ‘Economy Seen from Satellites,’ analyzing satellite image data from the domestic satellite service company Naraspace in relation to defense, industry, economy, society, and international affairs.