A Fine-Scale Mangrove Map of China Derived from 2-Meter Resolution Satellite Observations and Field Data

Tao Zhang,Shanshan Hu,Yun He,Yuhang Gan,Xiaomei Yang,Aixia Liu,Shucheng You

doi:10.3390/ijgi10020092

Abstract

Mangrove forests are important ecosystems in the coastal intertidal zone, but China’s mangroves have experienced a large reduction in area from the 1950s, and the remaining mangrove forests are exhibiting increased fragmentation. A detailed mangrove dataset of China is crucial for mangrove ecosystem management and protection, but the fragmented mangrove patches are hardly mapped by medium resolution satellite imagery. To overcome these difficulties, we presented a fine-scale mangrove map for 2018 using the 2-meter resolution Gaofen-1 and Ziyuan-3 satellite imagery together with field data. We employed a hybrid method of object-based image analysis (OBIA), interpreter editing, and field surveying for mangrove mapping. The field survey route reached 9500 km, and 2650 patches were verified during the field work. Accuracy assessment by confusion matrix showed that the kappa coefficient reached 0.98, indicating a highly thematic accuracy of the mangrove dataset. Results showed the total area of mangrove forest in China for 2018 was 25,683.88 hectares, and approximately 91% of mangroves were found in the three provinces of Guangdong, Guangxi, and Hainan. About 64% of mangroves were distributed in or near the nature reserves established by national or local governments, which indicated that China’s mangroves were well protected in recent years. The new fine-scale mangrove dataset was freely shared together with this paper, and it can be used by local authorities and research groups for mangrove management and ecological planning.

Highlights

IntroductionMangrove forests are distributed in the tropical and subtropical areas of the world between approximately 30◦ N and 30◦ S latitude [1,2]
Mangrove forests provide a wide range of ecosystem services such as shoreline stabilization, water purification, the provision of biological diversity and nursery habitats for marine fisheries, and they are important to the recreation and tourism industry [3,4,5,6]
In the process of the field work, we found sparsely distributed mangroves with canopy densities less than 20%, and these sparse forests were not included in the Mangrove China 2018 (MC2018) dataset either

Summary

Introduction

Mangrove forests are distributed in the tropical and subtropical areas of the world between approximately 30◦ N and 30◦ S latitude [1,2]. These forests consist of trees, shrubs, and palms that grow in harsh environmental settings including high salinity, high temperatures, extreme tides, high sedimentation, and muddy anaerobic soils [1]. Mangrove forests provide a wide range of ecosystem services such as shoreline stabilization, water purification, the provision of biological diversity and nursery habitats for marine fisheries, and they are important to the recreation and tourism industry [3,4,5,6]

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Methods

Results

Discussion

Conclusion