Mangroves map of China 2018 (MC2018) Derived from 2-meter resolution Satellite Observations and Field Data

Mangrove is an important ecosystem in the coastal intertidal zone, but since the 1950s, the area of Mangrove in China has decreased greatly. China's detailed mangrove data set is very important for mangrove ecosystem management and protection, but the medium resolution satellite images can hardly capture fragmented mangrove patches. To overcome these difficulties, we present here a detailed map of mangrove forests in 2018 using 2-meter resolution satellite images of gaofen-1 and ziyuan-3, as well as topographic data. We used a hybrid method of object-based image analysis (OBIA), interpreter editing and field investigation, and interpreted more than 300 scenes. The field survey route reached 9,500 kilometers, 2650 patches were verified and detailed information of 650 mangrove patches were collected during the field work. The accuracy evaluation was conducted with the confusion matrix. Two sources of ground truth points for accuracy assessment in this study: First, in June 2019, 223 points were obtained Guangdong, Guangxi, Hainan and Fujian by field survey; Second, 2,077 mangrove verification points were collected by field investigator from higher-resolution imagery of GoogleEarthTM and BingMapTM. Result shows that the overall accuracy of the data is 99.3%, the Kappa coefficient is 0.985, the mapping accuracy is 99.3%, and the user accuracy is 99.0%. The statistics from this dataset showed that the total area of mangroves in China in 2018 was 25683.88 hectares, of which 91% were distributed in Guangdong, Guangxi and Hainan provinces. About 64% of the mangroves are distributed in or near the nature reserves established by the national or local governments, which indicates that the mangroves in China have been well protected in recent years. In this paper, the new fine scale mangrove data set is shared free of charge to local authorities and mangrove ecological protection and research groups.