Earlier studies
As GIS-based spatial information services provided through the Internet are increasingly common today, various and precise spatial information that was not accessible in the past are available free of charge today. One of the most popular services is Google Earth, a spatial information service provided by Google, a multinational company, based on satellite spatial images. Google Earth has been utilized in various areas, and, in particular, it has been actively utilized to acquire geographic information on disaster and devastated areas of which changes over time are hardly accessible, and to identify the routes of spread by country.
Scientists around the world utilize Google Earth for various purposes for humanity such as predicting different types of natural disasters to secure the safety of airplanes, researching global warming, and tracing avian flue variations and the routes of spread. Moreover, it is also used to figure out the decisive evidence of global warming, and to forecast the melting of permanent snow caused by global warming. The National Snow and Ice Data Center (NSIDC) of Colorado University in the United States has continued to analyze satellite images to research glaciers in the polar areas, and also successfully proved the seriousness of global warming by animating the images of glaciers in the Arctic in a time-ordered sequence utilizing Google Earth. The NSIDC reported that over 50% of sea ice in the Arctic was melted within only two months.
Dr. Daniel Janies, a zoologist at the Ohio State University, tried to trace the routes of spread and variation process of H5N1 avian influenza that can infect humans by country utilizing Google Earth, and found that the share of abnormal routes such as bird smuggling, and other routes without transmission between birds or migratory birds is increasing.
Above all, the area that can show a significant amount of achievements by applying Google Earth to scientific research is predicting and monitoring natural disasters. The research team of Dr. Peter Webley in the Institute of Volcanology at University of Alaska developed the Precise Point Positioning (PPP) program for volcanic ash utilizing Google Earth, which highlights the utility of Google Earth. The Real Time Mission Monitor (RTMM) is a tool that integrates meteorological images updated in real time every minute through Google Earth with the flight paths of research aircraft, playing a key role in helping aircraft approach hurricanes avoiding unexpected risk factors such as lightning or gusts.
As such, Google Earth is mainly used to preemptively prevent disasters and to secure the safety of humans, but when natural disasters occur, it can be utilized to establish plans for rescue. It is because situations in disaster areas can be monitored in real time through Google Earth. It also allows to develop maps of emotions that integrate geographic information with sensory information, supporting reasonable urban development. Christian Nold, a designer in the United Kingdom, built data on emotional reactions of people towards certain urban areas, integrated them with Google Earth and created the world’s first two-way map that showed geographic information and human emotions simultaneously. As the map of emotions shows how people react to certain social places such as parks and squares, and to which point of intersection of roads people tend to show more emotional reactions, it can be utilized in establishing basic guidelines for urban development or plans for reasonable urban development.
In this study, Google Earth, an Internet-based geographic information service, was utilized as an alternative in order to overcome the limits of conventional geographic information. Google Earth provides satellite images of over 2.5m spatial resolution as basic data. For large cities or certain facilities, it provides 1m high-resolution satellite images. As
Fig. 1 shows, most of the high-resolution satellite images of North Korea provided by Google Earth were taken before 2000, covering nearly every region of North Korea. The high-resolution satellite images provided by Google Earth show the date and year when the images were taken (
Fig. 2).
In addition, there has been almost no study in Korea that researched the impact of nuclear tests on the environment of forests that will be examined through Google Earth in this study, and only few studies examined the destruction of forests.
People in North Korea have cut down trees in mountains for firewood, which turned them into bare mountains, and reduced the area of forests in North Korea by 30% over the past two decades (
Song, 2012). The ‘excessive conversion of forests into terraced fields’ has devastated forests in North Korea. The unplanned ‘development of terraced fields’ and the ‘new land development project’ have been pointed out as one of the causes of the worst-ever flood damage in the mid-1990s in North Korea (
Jung and Byun, 2011). In particular, regions like Hwanghaenam-do and Hwanghaebuk-do have relatively more low hills and slopes than other regions have experienced serious forest destruction due to the development of terraced fields and the new land development project that were conducted in order to secure agricultural lands. In addition, forest destruction and environmental pollution were found to broadly spread across North Korea centering on industrial cities (
Ki, 2016).
For this reason, it will be important to identify and establish measures against the effects of nuclear tests and consequent environmental destruction on the Korean Peninsula, even if they does not pose immediate deadly threats, in order to minimize damage from potential threats (
Jang, 2017). Most of the studies conducted in Korea, however, focus on political and economic environments associated with North Korea’s nuclear tests. Some studies were conducted in other countries on environmental destruction caused by nuclear tests, but they also researched their impact on the atmosphere, air, sea, soil, plants and humans only (
Pravalie, 2014). There has been no study that focused on forest destruction by nuclear tests. For this reason, this study that examines the impact of North Korea’s nuclear tests on environment, especially forest destruction, utilizing Google Earth is expected to give various implications.
Methods
With the aim of examining the environmental impact of North Korea’s nuclear test based on Google Earth spatial images, this study selected as a research subject the nuclear test site at Punggye-ri, Gilju-gun, Hamgyeongbuk-do, North Korea. North Korea conducted its first nuclear test in 2006, and most recently the sixth nuclear test in September, 2017 (
Fig. 3,
Table 1).
If there is any radiation leak and environmental destruction after nuclear tests in North Korea, it is necessary to analyze their actual level based on scientific and objective data. The satellite images of Google Earth used in this study provide 25m-resolution SPOT images as basic data, and 60cm-resolution QuickBird images are additionally available for major cities and military facilities. Most of the images were taken after 2005, and the date and year of the images were provided by Google Earth with images (
Bae, 2010).
In particular, images provided by Google Earth can be conveniently compared with those taken in the past using a function of viewing historical imagery. Users can also add an icon to spot an exact location by entering latitude and longitude information, which allows users to see how the environment of the place has changed over time visually. However, recent images for some areas are not available, and thus it is difficult to compare differences between the past and present conditions of those areas.
This study aimed to examine environmental destruction caused by six rounds of nuclear tests in North Korea by comparing images before and after the nuclear tests. In particular, areas related to forest destruction were focused on in this study. In many cases, forest destruction is associated with changes in geological and geographical features, which in turn accelerates radiation leaks or spreading. To do so, this study compared images before and after the nuclear tests in order to identify the location of each nuclear test and changes in the color and shape of their surrounding areas and thus to examine their impact. Despite the limitations of comparison based on Google Earth images, this study aimed to identify whether forest destruction was directly caused by nuclear tests or indirectly caused by earthquakes or landslides after nuclear tests, and to compensate the limitations through literature review.
The location of six nuclear test sites conducted in Punggye-ri identified on Google Earth images is as shown in
Fig. 3, and the conditions of surrounding areas before and after nuclear tests were as shown in
Table 1.
Fig. 3 shows the location and date of nuclear tests, and the magnitude of earthquakes caused by nuclear tests. Each nuclear test was carried out within very close proximity, and in particular those from the fourth to the sixth tests seemed to be conducted in almost the same place.