Abstract
Phenology-based multi-index with the random forest (RF) algorithm can be used to overcome the shortcomings of traditional deforestation mapping that involves pixel-based classification, such as ISODATA or decision trees, and single images. The purpose of this study was to investigate methods to identify specific types of deforestation in North Korea, and to increase the accuracy of classification, using phenological characteristics extracted with multi-index and random forest algorithms. The mapping of deforestation area based on RF was carried out by merging phenology-based multi-indices (i.e., normalized difference vegetation index (NDVI), normalized difference water index (NDWI), and normalized difference soil index (NDSI)) derived from MODIS (Moderate Resolution Imaging Spectroradiometer) products and topographical variables. Our results showed overall classification accuracy of 89.38%, with corresponding kappa coefficients of 0.87. In particular, for forest and farm land categories with similar phenological characteristic (e.g., paddy, plateau vegetation, unstocked forest, hillside field), this approach improved the classification accuracy in comparison with pixel-based methods and other classes. The deforestation types were identified by incorporating point data from high-resolution imagery, outcomes of image classification, and slope data. Our study demonstrated that the proposed methodology could be used for deciding on the restoration priority and monitoring the expansion of deforestation areas.
Highlights
Forest ecosystems provide ecological benefits to both humans and wildlife [1]
The normalized difference vegetation index (NDVI) consistently increased from March to June for forest, unstocked forest, and plateau vegetation during the growing season, and decreased during the period from August to October
The highest NDVI value of all land cover classes was observed in July and August
Summary
Growing global demand for food and fiber is accelerating the pressure on forest ecosystems around the world, from agriculture and logging [2]. Between 1990 and 2015, almost 40 percent of the forests in North Korea have either been converted to fields for food crop production, or cut down for fuel wood. This wide-spread deforestation has led to increased damage by natural disasters [4,5,6]
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