Annual Change Analysis of Mangrove Forests in China during 1986–2021 Based on Google Earth Engine

Abstract

Mangroves are a key type of protected coastal wetland, with a range of benefits such as protection from wave damage, sand fixation, water purification and ecological tourism. As the academic knowledge of mangroves has gradually increased, the use of remote sensing to monitor their dynamic changes in China has become a hot topic of discussion and has received attention in academic circles. Remote sensing has also provided necessary auxiliary decision-making suggestions and data support for the scientific and rational conservation, restoration and management of mangrove resources. In this paper, we used Landsat satellite series data combined with the normalized difference vegetation index (NDVI) and adaptive threshold partitioning (OTSU method) to monitor mangrove dynamics in coastal China from 1986 to 2021 based on Google Earth Engine (GEE), with three main results. (1) Based on the massive data and efficient computational capability of the GEE platform, we achieved large-scale interannual mangrove distribution extraction. The overall classification accuracy for 2019 exceeded 0.93, and the mangrove distribution extraction effect was good. (2) The total mangrove area and the mean patch size in China showed overall increasing trends, and Guangdong and Guangxi were the top two provinces in China in terms of the largest mangrove area. (3) Except for Dongzhaigang National Nature Reserve, the mangrove areas in other national mangrove reserves mainly showed increasing trends, confirming the effectiveness of the reserves. Data on the spatial structure and area trends of mangroves in China can provide scientific references for mangrove conservation and development, and serve in the further restoration of mangrove ecosystems.

MTF Measurement by Slanted-Edge Method Based on Improved Zernike Moments

“…The Otsu algorithm was proposed by OTSU N in 1979 [ 40 ]. It is mainly applied to digital image segmentation [ 41 , 42 ], and its main idea is to divide the image into foreground and background parts by using a threshold [ 43 , 44 , 45 ], to maximize the variance between foreground and background. Suppose the segmentation threshold is , the proportion of foreground pixels is , the average gray level is , the proportion of background pixels is , the average gray level is , the total average gray level of the image is , and the variance between-cluster is , then: …”

A Simulation Optimization Approach for Wetland Conservation and Management in an Agricultural Basin

“…By using GEE, it is possible to view and analyze all covers and uses of the earth with high spatial details in two and three dimensions. Many studies in different fields, such as vegetation monitoring [50], land use/cover maps [51] and their characteristics, such as the temperature of the earth's surface [52], monitoring of protected areas [53], monitoring of water resources and water bodies [54], agricultural products [55], and other types of remote sensing studies, have been carried out using this system.…”

Structure and composition of mangrove vegetation in the Lakkang Delta and Lantebung, Makassar City, South Sulawesi, Indonesia

“…Ecological function: In terms of physical protection, mangroves are a significant type of protected coastal wetland that guard against wave damage, fix sand, purify water, and encourage siltation and land creation. Wang et al (2022) resist disasters such as wind, hurricanes, and floods (Warpur, 2016). Vegetation mangroves, prevent the shore from eroding and stabilize it, The root system of mangrove vegetation can withstand erosion caused by sea waves (Farista & Virgota, 2021).…”

“…Sediments in the waves may be caught by mangroves (Raju & Arockiasamy, 2022). Chemical Aspect: Mangroves have a significant role in the carbon cycle and biodiversity (Hu et al, 2020), decreasing marine pollution, removing impurities from water, preserving the variety of marine organisms, and advancing the global carbon cycle, ecotourism, and science education (Wang et al, 2022). Biological function, habitat, spawning grounds, nursery grounds, and feeding grounds (Supriadi et al, 2015).…”