Satellite‐Based Mapping of South Manchurian Mixed Forests Highlights Critical Conservation Needs

Questions South Manchurian mixed forests (SMMFs) are among the most species‐rich forest ecosystems in the Northern Hemisphere's cold‐temperate zone. Across their range, native SMMFs have been largely replaced by secondary forests and other human‐modified vegetation. They continue to face significant threats from climate change, mismanagement, and anthropogenic pressures. Effective conservation requires a precise quantitative evaluation of the remaining SMMF area coupled with an estimation of their potential distribution. This study aims to assess the current area of SMMFs, evaluate their potential distribution, and analyze changes over time. Location Northeastern China, the southern Russian Far East, and the Korean Peninsula. Methods We mapped SMMFs using multi‐temporal satellite data. Specifically, we employed the Global Land Analysis and Discovery (GLAD) analysis‐ready Landsat time‐series for two reference years: 2001 and 2021. For classification, we applied a bagged regression tree algorithm. We trained the classifier on a dataset derived from field relevés and published literature records. For accuracy assessment and area estimation, we used a stratified sampling design based on the resulting maps. To estimate the potential distribution area of the SMMFs, we performed habitat suitability modeling, employing two machine learning algorithms: Random Forest (RF) and Extreme Gradient Boosting (XGBoost). The models were built using two independent, verified presence/absence point datasets. Predictors included topographic variables (elevation, slope, aspect) and key bioclimatic variables, including warmth and continentality indices, alongside a proxy for precipitation. Results We estimated the total area of SMMFs in 2021 at 4145.4 (SE ±876.4) km 2 . The largest area of these forests is preserved in Russia (34.0%). North Korea, China, and South Korea account for 31.4%, 29.9%, and 4.7% of the total SMMF area, respectively. The areas potentially suitable for these forests are estimated at 28,642.5 (SE ±9094.5) km 2 . Globally, the mean sample‐based estimate of current SMMF area represents only 20.2% of the estimated potential distribution area. Although severe historical declines in SMMF area have been documented, no significant changes have been detected over the past 20 years. Nowadays, SMMFs are highly fragmented and are largely confined to protected areas. Conclusions The new SMMF map is a critical tool for conservation, enabling the identification of priority forest areas and informing targeted strategies for their protection and restoration. Specifically, it provides the spatial foundation for optimizing protected area networks and designing biological corridors—essential measures for ecosystem restoration and the advancement of broader conservation objectives.