Impact of Deforestation on Agro-Environmental Variables in Cropland, North Korea

Deforestation in North Korea is becoming the epitome of the environmental change occurring in the Korean Peninsula. This study estimates the agro-environmental variables of North Korea’s croplands and analyzes the impact of deforestation using the GEPIC (GIS-based EPIC (Environmental Policy Integrated Climate)) model and time-series land cover maps. To identify the changes in agricultural quality under deforestation, wind erosion, water erosion, organic carbon loss, and runoff were selected as the agro-environmental variables having an impact on cropland stability and productivity. Land cover maps spanning the past three decades showed that 75% of the forests were converted to croplands and that 69% of all converted croplands were originally forests, confirming the significant correlation between deforestation and cropland expansion in North Korea. Despite limitations in the verification data, we conducted qualitative and quantitative validation of the estimated variables and confirmed that our results were reasonable. Over the past 30 years, agro-environmental variables showed no clear time-series changes resulting from climate change, but changes due to spatial differences were seen. Negative changes in organic carbon loss, water erosion, and runoff were observed, regardless of the crop type. On newly-converted agricultural lands, runoff is 1.5 times higher and water-driven erosion and soil organic loss are more than twice as high compared to older croplands. The results showed that the agro-environment affected by deforestation had an impact on cropland stability and productivity

접근불가지역인 북한의 시계열 토지피복도 매핑 및 산림 변화 동향 분석

학위논문(석사) -- 서울대학교대학원 : 농업생명과학대학 생태조경·지역시스템공학부(생태조경학), 2021.8. 이동근.North Korea, as an inaccessible area, has little research on land cover change, but it is very important to understand the changing trend of LULCC and provide information previously unknown to North Korea. This study therefore aimed to construct and analyze a 30-m resolution modern time-series land use land cover (LULC) map to identify the LULCCs over long time periods across North Korea and understand the forest change trends. A land use and land cover (LULC) map of North Korea from 2001 to 2018 was constructed herein using semi-permanent point classification and machine learning techniques on satellite image time-series data. The resultant relationship between cropland and forest cover, and the LULC changes were examined. The classification results show the effectiveness of the methods used in classifying the time series of Landsat images for LULC, wherein the overall accuracy of the LULC classification results was 97.5% ± 0.9%, and the Kappa coefficient was 0.94 ± 0.02. Using LULC change detection, our research effectively explains the change trajectory of North Korea’s current LULC, providing new insights into the change characteristics of North Korea’s croplands and forests. Further, our results show that North Korea’s urban area has increased significantly, its forest cover has increased slightly, and its cropland cover has decreased. We determined that North Korea’s Forest protection policies have led to the forest restoration. Thus, as agriculture is one of North Korea’s main economic contributors, croplands have been forced to relocate, expanding to other regions to compensate for the land loss caused by forest restoration.북한은 세계에서 가장 심각하게 황폐화된 산림 중 하나를 포함하고 있지만 최근에는 산림 복원을 강조하고 있다. 산림 복원이 일어나는 정도를 이해하기 위해서는 토지 이용과 토지 피복 변화 경향 (LULCC)을 이해해야 한다. 따라서 본 연구는 30m 해상도의 현대 시계열 토지 이용 토지 피복 (LULC)지도를 구성 및 분석하여 북한 전역의 장기 LULCC를 식별하고 산림 변화 추세를 이해하는 것을 목표로 한다. 2001 - 2018 년 기간 동안 국가의 LULC지도는 30m 해상도 위성 이미지 시계열 데이터를 기반으로 반영구적 포인트 분류 및 기계 학습을 사용하여 구성되었으며, 이는 GEE (Google Earth Engine)에서 수집 한 현상 학적 정보와 함께 사용되고 있다. 또한 LULCC 탐지기 법과 경작지 변화와 고도의 관계를 고려하여 2001 - 2018 년 북한의 산림 변화를 평가하였다. LULC 맵 결과의 전체 분류 정확도는 97.5 % ± 0.9 %이고, Kappa 계수는 0.94 ± 0.02 이다. LULCC 탐지는 또한 2001 - 2018 년에 북한의 산림 면적이 약간 증가한 것으로 나타났다. 일반적으로 산림 피복 면적은 크게 변하지 않았으나 남부와 중부 지역의 산림 복원과 북부와 서부의 경작지 상대적 증가 측면에서 뚜렷한 공간적 변화가 관찰되었다. 북한의 특성과 산림 정책 문서를 검토 한 결과 북한 근대 산림의 일부 지역이 복원되고 있음을 확인하였다.Chapter 1. Introduction 1 Chapter 2. Study Area 7 Chapter 3. Materials and Methods 8 3.1. Study overview 8 3.2. Data Collection 9 3.3. Data Processing 11 3.4. Classification Process 12 3.5. LULCC Analysis 14 3.6. Reference Data Collection and Classification Accuracy Validation 15 Chapter 4. Results 17 4.1. LULC Classification Accuracy Assessment 17 4.2. LULC Classification Results 20 4.3. LULC Change Detection 22 4.4. Relation with mountainous cropland and elevation 26 Chapter 5. Discussion 28 5.1. Interpretation and explanation of the forest change in North Korea 28 5.2. Importance of spatial analysis and future research directions 30 5.3. Limits and Advantages 32 Chapter 6. Conclusion 34 Bibliography 36 Appendix 44 Abstract in Korean 51석

Assessment of Agricultural Drought Considering the Hydrological Cycle and Crop Phenology in the Korean Peninsula

Hydrological changes attributable to global warming increase the severity and frequency of droughts, which in turn affect agriculture. Hence, we proposed the Standardized Agricultural Drought Index (SADI), which is a new drought index specialized for agriculture and crops, and evaluated current and expected droughts in the Korean Peninsula. The SADI applies crop phenology to the hydrological cycle, which is a basic element that assesses drought. The SADI of rice and maize was calculated using representative hydrological variables (precipitation, evapotranspiration, and runoff) of the crop growing season. In order to evaluate the effectiveness of SADI, the three-month Standardized Precipitation Index, which is a representative drought index, and rainfed crop yield were estimated together. The performance evaluation of SADI showed that the correlation between rainfed crop yield and SADI was very high compared with that of existing drought index. The results of the assessment of drought over the past three decades provided a good indication of a major drought period and differentiated the results for crops and regions. The results of two future scenarios showed common drought risks in the western plains of North Korea. Successfully validated SADIs could be effectively applied to agricultural drought assessments in light of future climate change, and would be a good example of the water-food nexus approach

Google Earth Engine을 이용한 북한의 산림 황폐화 연구

학위논문(석사) -- 서울대학교대학원 : 농업생명과학대학 생태조경·지역시스템공학부(생태조경학), 2021.8. 이동근.산림 황폐화는 산림 생태계를 파괴하며 물 저장 및 공급과 대기오염을 줄이는 등 산림이 가지고 있는 기능을 저하시킨다. 황폐화로 인한 산림의 기능 저하는 기후변화 대응 및 대기질 측면에서 부정적인 영향을 미치게 된다. 북한은 세계 3개 산림 황폐지역으로 1990년대부터 최근까지 산림의 약 28%가 황폐화되었다는 국립 산림 과학원의 연구결과가 있다. 하지만 공인된 통계는 없어 추후 복원을 위해서는 정확한 현황 파악이 필요한 실정이다. 일반적인 산림 황폐화와는 달리 북한은 경제적인 어려움으로 인한 식량 부족과 에너지 자원의 부족으로 발생하였다. 식량 공급을 위하여 산림은 밭으로 개간되었고, 석탄의 부족으로 인하여 에너지원으로 사용하기 위한 무분별한 벌목이 진행되어 광범위함 산림 황폐화가 가속화되었다. 산림 황폐화의 문제점은 북한에서도 인식하여 관련 정책을 진행하는 등의 노력을 하였지만, 지속되는 경제난과 한국과의 관계 악화로 인하여 효과적으로 이루어지지 않고 있다. 북한의 산림 황폐화는 북한뿐 아니라 한반도의 환경과 동북아에 사회 경제적으로 영향을 주고 있기 때문에 복원이 시급한 상황이며 추후 한국과의 관계가 개선되었을 때 효과적인 복원 사업 지원을 위해서는 정확한 현황과 규모를 파악하는 것이 중요하다. 북한은 현재 접근 불가 지역으로 현장조사를 통한 현황 파악이 불가능하기 때문에 위성영상을 사용한 원격탐사가 가장 효과적인 방법이다. 또한 산림 황폐화는 단기간에 나타나는 현상이 아니라 장기간에 걸쳐 진행되는 현상이기 때문에 다중시기로 분석할 필요가 있다. 따라서 본 연구에서는 북한의 산림 황폐화가 심화되기 시작한 1990년대 이후인 2000년부터 가장 최근인 2020년까지 20년 동안의 북한 산림 황폐화 현황을 파악하는 것을 기본으로 두 가지 연구 가설을 세워 리를 확인하고, 황폐화 진행이 얼마나 되었는지, 복원사업의 성과가 있었는지 살펴보고자 한다. 이를 통해 추후 복원 사업을 진행할 때, 체계적인 계획을 세울 수 있는 기초자료로 쓸 수 있도록 하는 것이 연구 목표이다. 이를 위하여 미국의 지리정보 플랫폼인 Google Earth Engine을 통하여 픽셀 기반 감독 분류 랜덤 포레스트(Random Forest) 방법을 사용하여 토지 피복 분류를 진행하고, 이를 기반으로 Change Detection(변화 감지)을 하여 어느 지역에서 황폐화가 진행되었는지, 산림 면적이 얼마나 변화하였는지 살펴보았다. 분석을 진행한 결과, 2000년-2010년 동안 북한의 산림 비율은 전체 면적의 약 72.5%에서 약 61%로 약 11.5% 정도 감소한 것으로 나타났다. 이와 반면에 농지와 나지의 비율은 각각 약 7%, 약 2% 증가한 것으로 나타나 무분별한 벌채와 개간으로 인한 산림 황폐화가 심각하다는 것을 보여준다. 변화가 가장 많이 나타난 지역은 평안도, 함경도, 강원도 지역으로 나타났으며, 변화가 가장 적게 나타난 지역은 황해도 지역으로 나타났다. 2010년-2020년 동안의 북한의 산림 비율은 약 61%에서 약 62%로 약 1%정도 증가하였으며, 농지도 약 3% 증가하였다. 이와 반면에 나지 비율은 약 4% 감소하여 본격적인 산림 복원 사업을 시작한 2016년 이후 산림 비율이 약간 상승하고 나지 비율이 감소하였으나 농지 비율이 증가한 것으로 보아 산림 복원이 성공적으로 이루어지지 않았으며, 무분별한 개간 또한 지속되고 있다는 것을 보여준다. 변화가 가장 크게 일어난 지역은 황해도, 함경도 강원도 지역으로 나타났으며, 변화가 가장 적게 일어난 지역은 평안도 지역으로 나타났다. 20년 동안 공통적으로 변화가 많이 일어난 지역은 함경도 강원도로, 분석결과를 통해 이 지역에서 개간과 벌채가 많이 일어났음을 알 수 있다.Deforestation destroys forest ecosystems and reduces the functions of forests, such as reducing water storage and supply and air pollution. The degradation of forests due to deforestation harms climate change response and air quality. North Korea is one of the world's three deforested areas, and according to the research results of the National Institute of Forestry and Science, about 28% of the forest has been degraded from the 1990s until recently. However, as there are no official statistics, it is necessary to accurately identify the current situation for future restoration. Unlike general deforestation, North Korea was caused by a shortage of food and energy resources due to economic difficulties. Forests were cleared into fields for food supply, and extensive deforestation was accelerated by indiscriminate logging for use as an energy source due to a lack of coal. Although North Korea has recognized the problem of deforestation and implemented related policies, it has not been effectively implemented due to the continuing economic difficulties and deterioration of relations with South Korea. Since deforestation in North Korea has a socio-economic impact on North Korea and the environment on the Korean Peninsula and in Northeast Asia, restoration is urgently needed. In addition, it is important to know the exact current status and scale of deforestation for effective restoration project support when relations with Korea improve in the future. Since North Korea is currently inaccessible and it is impossible to determine the current situation through field surveys, remote sensing using satellite imagery is the most effective method. In addition, since deforestation is not a short-term phenomenon, but a long-term phenomenon, it is necessary to analyze it in multiple periods. Therefore, in this study, the status of deforestation in North Korea for 20 years from 2000 to 2020 after the 1990s, when deforestation in North Korea began to intensify, was identified, and two research hypotheses were established and confirmed. This study aims to enable it to be used as basic data for systematic planning when conducting a restoration project in the future. To this end, land cover classification is carried out using the pixel-based supervised classification random forest method through Google Earth Engine, a geographic information platform in the United States, and based on this, change detection is performed to determine the extent of devastation in an area. We looked at the progress and how much the forest area had changed. As a result of the analysis, the proportion of forests in North Korea decreased by about 11.5% from about 72.5% of the total area to about 61% from 2000 to 2010. On the other hand, the ratio of cropland and bareland increased by about 7% and about 2%, respectively, indicating that the deforestation caused by reckless logging and clearing is serious. The regions with the most changes were Pyeongan-do, Hamgyeong-do, and Gangwon-do, and the region with the least change was Hwanghae-do. During 2010-2020, the proportion of forests in North Korea increased by about 1% from about 61% to about 62%, and the cropland also increased by about 3%. When the full-scale forest restoration project began in North Korea, the ratio of bareland decreased by about 4% and the ratio of the forest increased slightly. Hwanghae-do and Gangwon-do, Hamgyeong-do showed the largest change, and Pyeongan-do show the least change. Gangwon-do, Hamgyeong-do, has seen many changes in common over the past 20 years, and the analysis results show that clearing and logging took place a lot in this area.Chapter 1. Introduction 2 1.1. Study Background and Purpose of Research 2 Chapter 2. Literature Review 5 2.1. Deforestation of North Korea 5 2.2. Random Forest using GEE 9 2.3. Change Detection 12 Chapter 3. Materials and Methods 14 3.1. Study Area and Materials 14 3.1.1. Study Area 14 3.1.2. Materials 15 3.2. Methods 21 3.2.1. Dataset and Pre-processing 21 3.2.2. Random Forest using GEE 22 3.2.3. Change Detection 23 Chapter 4. Results and Discussions 24 4.1. Results of Radom Forest 24 4.2. Results of Change Detection 28 4.2.1. 2000-2010 28 4.2.2. 2010-2020 30 4.2.3. 2000-2020 32 4.2.4. Regional Results 33 4.3. Discussions 46 Chapter 5. Conclusion 48 Bibliography 50 Abstract in Korean 55석

Spatiotemporal approach for estimating potential CO2 sequestration by reforestation in the Korean Peninsula

A forest is one of the carbon sinks in the terrestrial ecosystem; it is a major target for securing CO2 sequestration to achieve carbon neutrality. Reforestation is a forest management method that could attain carbon fixation and forest degradation recovery at the same time, but quantitative research has not been actively conducted. The purpose of this study is to identify the target areas for reforestation through changes in land cover in the Korean Peninsula and to quantify the potential CO2 sequestration effect of reforestation. According to the land cover change through satellite imagery, the area of settlements in the Republic of Korea (ROK) was the most dominant (+3,371 km2), and the main change occurred from cropland to settlements. The forest area increased by +1,544 km2 from 68,264 km2 in the 1980s to 69,809 km2 in the late 2010s. The forest decreased by 7,526 km2, accounting for 5.68% of the entire land area of the Democratic People's Republic of Korea (DPRK), and cropland increased by 5,222 km2 which is 5.12%. Assuming that the target of reforestation is an area whose land cover was a forest in the past and then converted to cropland, wetland, or bare ground, the area of the target decreased as the reference period was applied more recently. As a result of comparing the late 2000s to the late 2010s, the ROK's annual net carbon sequestration due to reforestation is predicted to be 10,833,600 Mg CO2 yr−1 in 2050 and 20,919,200 Mg CO2 yr−1 in 2070. In the DPRK, 14,236,800 Mg CO2 yr−1 in 2050 and 27,490,400 Mg CO2 yr−1 in 2070 were predicted. Reforestation in the Korean Peninsula was analyzed to have sufficient potential to secure a carbon sink, and the DPRK in particular was analyzed to be able to play a role in overseas reforestation