Quantitative studies of mangrove leaf functional traits will help us understand the adaptive evolutionary strategies of mangrove plants and the relationship between mangrove biodiversity and ecosystem functions. Because of the special environment of the intertidal zone where mangroves are located, it is very difficult to obtain the functional traits of mangrove canopies from the ground, and relevant studies are lacking. The maturity of Unmanned Aerial Vehicle (UAV) hyperspectral remote sensing technology provides a new means of conducting such research. This study considered mangroves on Qi'ao Island, Zhuhai, as the research object. Based on UAV hyperspectral data, two UAV hyperspectral data processing methods, which combined Partial Least Squares Regression with Normalized Difference Vegetation Index (PLSR+NDVI) and Partial Least Squares Regression with Continuous Wavelet Transform (PLSR+CWT), were used to estimate the 10 canopy leaf functional traits of mangroves on Qi'ao Island. The results showed that the PLSR + NDVI method was more suitable for the inversion of mangrove canopy-specific leaf weight (LMA), phosphorus content per unit mass (P_mass), and nitrogen content per unit area (N_area), whereas the PLSR + CWT method was more suitable for the estimation of the nitrogen/phosphorus ratio (N/P), chlorophyll content (C_ab), and carotenoid content (C_xc). However, the results of the above two methods for retrieving the nitrogen content per unit mass (N_mass), potassium content per unit mass (K_mass), phosphorus content per unit area (P_area),and potassium content per unit area (K_area) were not ideal (R²<0.3). The optimal method established in this study was used to estimate the contents of LMA, P_mass, N_area, N/P, C_ab, and C_xc of the mangrove canopy leaves in the study area and map their spatial distribution. Mangrove canopy leaf functional traits obtained using UAV hyperspectral data inversion better reflect the horizontal structure and function of the mangrove community. Regarding the spatial distribution patterns of canopy leaf functional traits, the spatial distribution patterns of N_area, C_ab, C_xc, and N/Pwere relatively consistent with higher values in the middle region and lower values in the edge region. The spatial distribution patterns of the LMA and P_mass were similar, and the distribution was relatively uniform throughout the study area. Combined with ground survey data, the internal relationship between species composition and spatial patterns of functional traits, as well as ecosystem functions and processes, can be deeply explored, and rapid investigation and assessment of mangrove forests can be realized at the community and ecosystem scales. The spatial distribution pattern of functional traits was closely related to the spatial distribution pattern of canopy structure and species. The inversion model of hyperspectral functional traits was constructed by separating mangrove species with different life types, which is expected to further improve the inversion accuracy of the model. Constructing a specific functional trait inversion model for each mangrove species, combined with the species identification results of visible-light images, will effectively improve the inversion accuracy of mangrove canopy leaf functional traits.

Mangroves are typical ecosystems located in the intertidal zone of tropical and subtropical coasts that protect the area against wave action, promote accretion in river estuaries, and act as an important global carbon sink. However, several natural mangroves have recently degraded due to climate change and human activities, increasing the risk to coastal areas' ecological environments. The mangroves on Qi'ao Island in Zhuhai, China, have been destroyed by human activities and the invasion of the exotic species Spartina alterniflora. In 1999, the Zhuhai municipal government imported pioneer species, such as Sonneratia apetala, to Qi'ao Island to restore the degraded mangroves, which have now evolved into a sufficiently continuous community with a stable area since 2015 with S. apetala as the dominant species. However, because the intensity and frequency of typhoon landfalls are increasing under global warming, dominant species in the mangroves of Qi'ao Island, S. apetala, is more vulnerable to typhoon disturbance due to its height and low trunk density, leading to greater uncertainty regarding their ecological functions on Qi'ao Island. Existing studies have mainly focused on the damage and recovery patterns of mangroves by a single typhoon, having seldom analyzed the response process of mangroves to consecutive disturbances by multiple typhoons; thus, these studies cannot be used to predict the succession process of mangroves with increasing typhoon frequency. In this study, the damage and recovery patterns of mangroves on Qi'ao Island were studied under the disturbance of three consecutive typhoons (2016 NIDA, 2017 Hugo, and 2018 Mangkhut), and their influencing factors were discussed based on the Normalized Difference Vegetation Index (NDVI) using Sentinel-2 remote sensing images. The results showed that (1) the NDVI of mangroves on Qi'ao Island decreased after the typhoon, and the damage levels could be classified as mild or mild to moderate. Moreover, the severity of the damage was relatively small. (2) An annual legacy effect existed across multiple typhoons. The recovery process of mangroves generally followed a circulating succession mode after typhoon disturbances in the order of more severe damage→slow recovery→milder damage→rapid recovery→ more severe damage pattern. (3) The damage levels of mangroves on Qi'ao Island increased with typhoon intensity. However, they decreased if S. apetala recovered slowly before the typhoon. Thus, the recovery pattern was mainly influenced by the damage levels of S. apetala after the typhoon landing and was not largely dependent on the hydrothermal conditions at regional scales. The results suggest that mangroves on Qi'ao Island, mainly consisting of S. apetala,have evolved to adapt to the consecutivetyphoon disturbances, which has promoted their succession from plantations to near natural forests and the formation of a stable typhoon-resistant ecosystem.

Mangroves are halophytic forest plant communities located on saline marshes in estuaries of tropical and subtropical bays. They are one of the most vulnerable ecosystems in the world and are severely threatened by urban development, environmental pollution, aquaculture, and other problems. The Dongchong mangrove forest is a relatively well-preserved mangrove forest in China, with a large area and a typical Excoecaria agallocha landscape, which has significant ornamental and ecological conservation value. The aim of this study is to provide basic support not only for mangrove ecological conservation and restoration, but also to construct and manage nature's reserves. The eco-environmental geological characteristics of mangroves were investigated using geology, geomorphology, pedology, ecology, and other methods, and a typical eco-environmental geological profile of the mangrove in Dongchong was drawn. The results show that the strata in the study area are mainly Quaternary sediments and rhyolites of the Nanshancun Formation of the Early Cretaceous. Faults are developed in the west of Dongchong Mangrove Wetland Park. The main environmental geological problems are uneven ground settlement, ground subsidence, and ground cracks. The concentration of F^- in the surface water are high, and the water quality is slightly lower than that of the Class III water standard; however, the groundwater is freshwater with low salinity and hardness. Cd and Tl are locally significant in the surface soil of the study area. N, P, CaCO₃, Org, and B are deficient in the soil, whereas the K content is mainly medium. A part of the soil is polluted by heavy metals, particularly As, followed by Cd. However, the mangrove leaves are rich in nutrients, indicating that the lack of soil nutrient elements and heavy-metal pollution are not the major factors limiting the growth of mangroves in this region. Improving the growth environment of mangroves should include expanding the landscape area and reinforcing reserve management. In the rock-soil-plant ecosystem, As, Pb, Cd, and B are significantly rich in the soil, indicating that their contents have a slight correlation with their parent rocks. Ni, Cu, Zn, and K are limited by the parent rock contents, and some elements including P, Mo, and Cr show enrichment capacity in the soil. The BCF >2 of mangroves of the mangrove forests in Dongchong are P and B, indicating that the mangrove trees have a higher absorption capacity for P and B. In contrast, the BCF values of As, Pb, and Cd are relatively low, which, in addition to the weak absorption capacity of the mangrove trees for these elements and combined with the geochemical characteristics of the soils in the study area, are also affected by the high Cd and As contents of the soil. All the data presented in this paper are from the project, "Ecological and Environmental Geological Survey of Shenzhen Nature Reserves," for which we express our sincere gratitude.

Mangroves, which have extremely high primary productivity, are efficient coastal blue carbon ecosystems. Aboveground biomass (AGB) is an important component of vegetation carbon pools. Thus, accurate estimation of mangrove AGB is critical for studying carbon cycle and climate change. While the practical significance and application of information obtained on mangrove AGB in China is apparent, studies of this nature in China at a national scale have rarely been reported. Remote sensing technology is convenient, efficient, has a wide observational range, and can be used for large-scale ecosystem monitoring. Canopy height is a structural parameter that is positively correlated with the AGB of vegetation. The Global Ecosystem Dynamics Investigation (GEDI) spaceborne Light Detection and Ranging (LiDAR) satellite, launched in recent years, is able to obtain vegetation canopy height. This study employed forest canopy height derived from GEDI satellite-based LiDAR and an allometric equation based on the allometric theory to estimate mangrove AGB in China in 2019, and the quantitative and spatial distribution of mangrove biomass and their main influencing factors were analyzed. The results showed that the total and mean AGB of mangroves in China in 2019 were about 1,974,827 t and 73.0 t/hm², respectively. Guangdong-Hong Kong-Macao area showed the largest total mangrove AGB, reaching 843,836 t. The mean values of AGB in each province (region) with mangrove ecosystems nationwide ranged from 53.3 to 92.1 t/hm², of which the largest was found in Hainan Province, reaching 92.1 t/hm². In Hainan, Taiwan, and Fujian provinces, mean mangrove AGB was higher than the national mean. Considering nature reserves, the mean AGBs of mangroves in Neilingdingdao-Futian and Mai Po mangrove nature reserves in Shenzhen Bay in the Guangdong-Hong Kong-Macao area and Dongzhaigang mangrove nature reserve in Hainan province were relatively high, with values greater than 110 t/hm². The accumulation and distribution of mangrove AGB in China are affected by latitude and anthropogenic factors. This study provides a comprehensive analysis of mangrove AGB in China based on remote sensing and an allometric equation and can provide a database and technical reference for estimating carbon storage in mangrove ecosystems. It will also contribute to the implementation of ecological restoration and protection measures for coastal mangroves, as well as carbon emission control in China.

Accurate mangrove biomass measurement is necessary for the management and protection of mangrove ecosystems. Sonneratia apetala was the first high-quality mangrove species to be introduced for mangrove restoration in China. Compared with other mangrove species, Sonneratia apetala has higher productivity and can store large amounts of carbon in its living biomass. However, accurate depiction of the single-wood canopy of Sonneratia apetala is challenging because of its high clumping density and intricate canopy structure. While traditional satellite remote sensing focuses on regional or larger-scale monitoring needs, the newly emerged Unmanned Aerial Vehicle (UAV) remote sensing has significant advantages for monitoring mangroves at finer scales. However, few studies have used UAV data for mangrove biomass analyses. In this study, we successfully used consumer-grade UAV data to estimate the height and aboveground biomass (AGB) of Sonneratia apetala on Qi'ao Island, Zhuhai, Guangdong Province. We used a variable window filter algorithm to detect the treetops. Individual tree canopy segmentation was performed using the seed region-growing algorithm. Additionally, we constructed a regression equation for height (H) and diameter at breast height (DBH) of Sonneratia apetala in the study area and optimized the traditional allometric equation. Finally, mangrove AGB was estimated at the tree level using the optimized allometric equation, and the results indicated that the AGB of Sonneratia apetala could be accurately extracted using UAV images. The accuracy of the tree delineation was 67%, the correlation between H and DBH was DBH = 2.2726H-6.4415, and the correlation coefficient R² was 0.8713. The aboveground mass of a single wood of Sonneratia apetala in the study area ranged from 29.60 to 388.44 kg, with a mean value of 145.72 kg and a total aboveground mass of 368.97 t. Partial spatial clustering was observed in the distribution of the aboveground mass of Sonneratia apetala in the study area, with a Moran's I index value of 0.594. The aboveground mass of Sonneratia apetala at the edge of the area and in the window part of the area was found to be smaller, mainly for two possible reasons. First, the natural death of Sonneratia apetala in part of the study area created a window, but its surrounding seedlings were still in the biomass accumulation stage. Second, the aboveground mass of Sonneratia apetala at the edges of the study area is often lost due to its vulnerable nature and anthropogenic factors. The average number of Sonneratia apetala in each quadrat was 6.3 and the AGB in the study area ranged from 2.99 to 247.24 t/hm², with a mean value of 92.14 t/hm². The estimated AGB based on UAV data was consistently lower than that generated from field data. The methods described in this study offer the possibility of easily repeatable, low-cost UAV surveys, providing a faster and more economical approach for monitoring mangrove forests than traditional ground surveys. These results may assist in decision-making regarding ecological monitoring, resource use, mangrove introduction, and scientific advancement of mangroves in China.

Mangroves occur in coastal intertidal zones and play an important role in terrestrial and marine carbon cycles. Accurate estimations of mangrove carbon stocks and sequestration potential can help quantify the contribution of mangroves to addressing climate change and achieving carbon neutrality goals. The carbon stocks and burial rates of different mangrove communities and regions in Guangdong Province were studied through literature collection and data integration. The soil carbon densities of the Rhizophora stylosa and Bruguiera gymnorhiza communities were 0.27 and 0.23 Gg C/hm², respectively, while the soil carbon density of the Kandelia obovata community was the lowest at only 0.13 Gg C/hm². The area of mangroves in Guangdong Province is 9,106.2 hm², the total carbon stock is 1,542.02 Gg C, and the soil carbon density is 0.23 Gg C/hm². The total carbon reserves of mangroves in thirteen regions are in the following order: Zhanjiang (894.5 Gg C) > Yangjiang (195.4 Gg C) > Jiangmen (97.7 Gg C) > Zhuhai (91.0 Gg C) > Maoming (59.6 Gg C) > Shantou (51.4 Gg C) > Zhongshan (49.2 Gg C) > Huizhou (36.1 Gg C) > Guangzhou (35.1 Gg C) > Shenzhen (18.3 Gg C) > Shanwei (10.8 Gg C) > Dongguan (2.83 Gg C) > Chaozhou (0.11 Gg C). Using the ²¹⁰Pb method, the sediment accretion rate was found to be 13.47 mm/a. Qi'ao Island had the highest sediment compaction rate of 31.5 mm/a, followed by Zhenhai Bay, with 16.5 mm/a, Shenzhen Futian, with 15.9 mm/a, and Leizhou Bay, with the lowest sediment compaction rate of 7.3 mm/a. The carbon sequestration capacity of Guangdong province is approximately 19.72 Gg C/a, with the Leizhou Peninsula having the highest (6.05 Gg C/a) and Futian, Shenzhen having the lowest (0.66 Gg C/a) capacities. The carbon storage of mangroves in Guangdong Province was 1,542.02 Gg C, which was higher than that in other regions. The carbon sequestration capacity of the mangroves was relatively strong. Therefore, the protection and restoration of local mangroves may substantially contribute to the mitigation of climate change while providing additional benefits. This assessment, on a provincial scale, provides insights into blue carbon sequestration capacity, thus contributing to the synchronous progression of blue carbon management.

Mangroves are woody wetland communities that grow in the intertidal zones of tropical and subtropical coasts and are among the most productive ecosystems in the world. Mangroves provide important support for coastal ecological and environmental protection, social development, and economic progress. Those found in Southeast Asia are a key portion of global mangroves. The study of spatiotemporal changes of mangrove forests and their driving factors in Southeast Asia can provide a theoretical basis and supportive evidence for the scientific protection and effective management of mangrove ecosystems. Based on the cloud computing platform of the Google Earth Engine, Landsat satellite data, and mangrove distribution data sets, combined with the Theil-Sen median trend analysis and Mann-Kendall test methods, this study analyzed the spatial variation trend of mangroves in Southeast Asia from 1990 to 2020. A factor detector and an interaction detector in the geographic detector method were used to quantitatively analyze the driving factors. First, the results showed that, from 1990 to 2020, the overall mangrove area in Southeast Asia showed a downward trend, with an area reduction of 1,467,883.1 hm² and an annual average loss rate of 1.1%. According to the statistics of the mangrove area change rate based on cellular network data, the total loss of mangrove area was as high as 40.11%. Of the total mangrove area, the regions with a change rate between -99% and -50% accounted for 28.57%, regions with a change rate between -49% and -5% accounted for 8.79%, and regions with a change rate between -4% and -1% accounted for only 13.95%. Regions with a change rate between 1% and 99% accounted for 8.18%. Only 0.4% of the mangrove area remained unchanged. The regions with increased mangrove area were primarily distributed in the Philippines, western and eastern Indonesia, and northern Vietnam. Second, the improvement and degradation of mangroves in Southeast Asia showed a concomitant distribution from 1990 to 2020. The degradation area of mangroves (79.25%) was much larger than the improvement area (20.32%) in Southeast Asia. Specifically, the significantly degraded areas accounted for 31.58%, the slightly degraded areas accounted for 47.67%, the significantly improved areas accounted for 4.75%, the slightly improved areas accounted for 15.57%, and only 0.42% of the area remained stable. Finally, the increase in aquaculture pond area was the main driving factor for mangrove area decline, with q values above 30%. Additionally, the shortest distance of mangroves from roads and population changes also had significant effects on the decline of mangrove area. The average annual temperature, precipitation, and topography had a relatively low degree of influence on mangrove changes. The results of the interaction detector indicated that all factors showed interaction enhancement, and the interaction between the culture tank and other factors was significantly stronger than that between other factors. The single factors with relatively weak driving force, such as average annual rainfall, temperature, and topography, had a significantly stronger influence on the interaction with other factors and showed a nonlinear enhancement effect.

Human activities such as deforestation, farming, and uncontrolled construction have had a negative impact on mangrove areas in the Reserve. This paper explores how the mangrove area and space have changed since the establishment of the Dongzhaigang Mangrove Nature Reserve, as well as the relationship between this change and the community residents around the Reserve. Six remote sensing images, from 1976 to 2021, were used to obtain wetland data of different ages in the Dongzhaigang Mangrove Forest Nature Reserve in Haikou City. Using the transfer matrix, a questionnaire survey, and principal component analysis, we analyzed the changes in mangrove forests in protected areas and their relationship with surrounding communities over the past 45 years. The results show that: (1) From 1976 to 2021, the area of mangroves in the reserve has increased from 1,395.84 hm² in 1976 to 1,589.28 hm² in 2021, showing a trend of "suddenly slowing and rising" during this period, and the proportion of mangrove area has increased from 28.6% in 1976 to 32.6% in 2021, becoming the main wetland type. The largest decline (250 hm²) in the mangrove area was from 1976 to 1985. The largest growth occurred from 2005 to 2018, when the mangrove area increased by 190.08 hm². (2) From 1976 to 2021, 91.77 hm² of mangrove wetlands in the study area were converted into other wetlands, 10.71 hm² were converted into non-wetlands, and 267.71 hm² of other wetlands and 28.21 hm² of non-wetlands were converted into mangrove wetlands. In the same period, the transfer targets of mangrove forests in the reserve were muddy beaches (34.32 hm²), rivers (25.81 hm²), marine aquaculture farms (21.06 hm²), other land (10.58 hm²) and flooded wetlands/interiors. Land flats (8.26 hm²); silt beaches (177.41 hm²), rivers (38.18 hm²), other land (28.21 hm²), deltas/sands/sand islands (22.15 hm²), flooding Wetlands/inland tidal flats (21.79 hm²), and paddy fields (6.34 hm²) are the most common areas transferred into mangroves. (3) Fishing income from surrounding community-dwelling individuals was significantly associated with farming, disfiguring forest-digging pond areas, conservation awareness, and mangrove area variation. The factor quality of fishing practices (cos2), values of fishing practices and income, months of fishing, fishing volume, and conservation attitude in the surrounding community residents accounted for more than 0.6 in the principal component analysis of area change of mangrove forests, where the factor quality of fishing practices and fishing income were more than 0.8. The decline in residential fishing frequency corresponds with the shift in household income sources, the occupational move from fishing to wage and service industries, the obvious increase in conservation awareness and the conservation attitude of residents, and the transformation of the mangrove area away from serious destruction to less fragmentation. The contributions of freshwater farms, resident population, number of secondary schools, and village to mangrove distance factors were all greater than 10 and negatively correlated with mangrove area change. Therefore, it is necessary to explore the relationship between mangroves and community residents to obtain a scientific reference for the utilization, protection, restoration, and management of mangroves in the Dongzhaigang Mangrove Nature Reserve.

Mangroves are one of the most important wetland ecosystems. The development of fisheries in tropical and subtropical bays or estuaries is closely associated with mangroves since the high heterogeneity of the mangrove ecosystem provides a suitable habitat for marine organisms. However, multiple factors have led to a significant reduction in mangroves, such as water pollution, disease, insect pests, invasive alien species, and climate change. It is crucial to understand the relationships among organisms, as well as the interactions between organisms and their environment, by studying the ecological niche width and overlap of species. Therefore, two new perspectives of ecological niche width and ecological niche overlap were used to understand the interspecific ecological relationships, competition mechanisms, and resource utilization status of fish communities in mangrove forests. Based on the data collected during seasonal sampling in July 2019 (summer), October 2019 (autumn), January 2020 (winter), and May 2020 (spring) in the Nanliujiang Estuary, the index of relative importance (IRI), Shannon index, and Pianka index were employed to analyze the temporal and spatial niche of the main fish species in the mangrove creeks and to study niche differentiation among the main fish species by redundancy analysis. A total of 17,680 individual fish were collected in this study, belonging to 12 orders, 23 families, 37 genera, and 45 species. Ten main fish species with IRI>100 were identified. Among the main fish species, the temporal niche breadth ranged from 0.46 to 1.78, with the highest of which belonging to Butis butis (1.78) and the lowest belonging to Pseudogobius javanicus (0.46). The spatial niche breadth ranged from 0.81 to 2.05, with the highest of which belonging to Synechogobius ommaturus (2.05) and the lowest belonging to P. javanicus (0.81). The spatiotemporal niche breadth of six species was greater than 2 (wide-niche species) that included Mugil cephalus, Coptodon zillii, Bostrychus sinensis, S. ommaturus, B. butis, and Pisodonophis boro. With regard to overlap, the temporal niche overlap between M. cephalus and P. javanicus was the highest (0.928), whereas that between Ambassis urotaenia and Terapon jarbua (0.001) was the lowest. The spatial niche overlap between A. urotaenia and Gambusia affinis was the highest (0.979), whereas that between M. cephalus and P. javanicus (0.178) was the lowest. Finally, the spatiotemporal niche overlap between C. zillii and P. javanicus was the highest (0.822), whereas that between A. urotaenia and Terapon jarbua (0.001) was the lowest. The two-dimensional temporal and spatial niche pairs in the mangrove creeks of the Nanliujiang River Estuary significantly overlapped (Q_ik > 0.6), accounting for 6.7% of the total species pairs, indicating that the temporal and spatial distributions of species were quite different and the temporal and spatial niche overlap was affected by seasonal changes. Redundancy analysis revealed that the main factors affecting spatiotemporal niche differentiation of the main fish species in the mangrove creeks of the Nanliujiang Estuary were water temperature, salinity, and Chlorophyll a. And the main fish biomass in winter was positively correlated with salinity; the main fish biomass in spring was positively correlated with dissolved oxygen, pH and Chlorophyll a; the main fish biomass in summer was positively correlated with total organic carbon, water temperature and Chlorophyll a; the main fish biomass in autumn was positively correlated with total nitrogen, turbidity and total phosphorus.

As an important land and water transition zone on Earth, wetlands are good places for birds to breed and roost. Bird monitoring has become an important index for assessing the biodiversity and ecological environment of a region. Nansha Wetland Park in Guangzhou is rich in biological resources and provides an important resting and wintering ground for global migratory birds as it is located on their migration route from East Asia to Australasia. To understand the migration patterns and annual dynamic changes of birds in the Nansha Wetland Park, line- and point-transect surveys were conducted to collect bird species and abundance data from January 2014 to December 2018. First, our results showed that 139 birds were recorded during the study period, of which migrant species were dominant. Combined with the available literature, a total of 186 bird species were recorded, belonging to 17 orders and 49 families. Of these bird species, 165 are under various levels of protection. Second, while the interannual changes in bird abundance were substantial, those of bird species richness were not, indicating that bird species tended to reach maximum abundance in bird communities. When compared to bird abundance in 2015, the number of individuals was relatively stable in other years of investigation, and the number of investigated species was the highest in 2017. Finally, monthly changes in bird species were in accordance with the annual rhythms of migration. Specifically, bird species richness increased rapidly during the wintering period, but remained constant during the breeding period. In addition, the migration time of waterbirds tended to increase over time. This may be related to a warming climate that prompts birds to migrate earlier. Differences in habitat patches are important influencers of bird feeding habits, and thus bird distribution and habitat. Among the habitat patches investigated, birds were primarily distributed in shallow tidal flats with rich food sources and in tall and lush mangrove communities, such as those containing the species Sonneratia apetala. Notably, the number of Platalea minor, a key indicator bird species, has increased steadily, with an increase of 346.15% from 26 in 2014 to 116 in 2018. The annual and monthly dynamic changes of birds in different areas showed subtle changes in individual numbers but generally showed a stable trend, which may be related to the environmental capacity of the habitat. The number of species and individuals that can be sustained by the environment tended to be saturated; that is, the maximum number of species that can be accommodated by the Nansha Wetland Park. Taken together, these findings suggest that bird species diversity could be promoted by expanding the area of tidal flats, increasing the planting area of mangroves, reasonably reclaiming wetlands, and maintaining the proportion of shallow water tidal flats and mangroves.

Mangroves have critical ecological functions and social and economic value, and are an important target for protection in the coastal wetland ecosystem. By monitoring long-term dynamic changes in mangrove ecosystems, the overall change process can be systematically and accurately recorded, providing data support and a basis for decision-making on scientific protection and effective management of the ecosystem. This study focuses on mangrove forests in coastal areas of Guangdong Province. A map of the mangrove forest, from 1986 to 2018, was made using Landsat remote sensing image based on Google Earth Engine (GEE),which is a cloud computing platform. The Random Forest (RF) method was used to extract mangrove trees from 32 periods from 1986 to 2018, in Guangdong Province. The interannual variation in mangrove characteristics in coastal cities of Guangdong province were compared. In addition, the evolution characteristics of mangrove patches in Guangdong province were analyzed. The results show that 1) The computing capacity and massive data of the GEE cloud platform provide data support for analyzing the inter-annual evolution of mangroves in Guangdong province, which greatly improves the computing efficiency. From 1986 to 2018, the overall classification accuracy of mangrove remote sensing was higher than 90%, with high classification accuracy and reliable results. In general, the coastal mangrove area of Guangdong province first decreased and then increased, and the range of change gradually declined after 2014, remaining at about 11 000 hm². Mangrove forests are unevenly distributed in the province and occur mainly in the west. 2) Concerning coastal cities, mangroves are distributed in 14 cities, among which Zhanjiang and Yangjiang have the largest mangrove area, which is about 70% of the mangrove area of Guangdong province. The mangrove area changes in each city fall under three categories: decreasing first and increasing later, increasing fluctuation, and no obvious change. 3) From 1986 to 2018, the overall number of patches in mangrove forests in Guangdong province showed a decreasing trend, but the average patch area (MPS) showedan increasing trend, and mangrove fragmentation was reduced. In 2018, the mangrove MPS was 4.11 hm² in Guangdong province, and the total number of patches was 2 782. From 1986 to 2018, when the change trend of MPS in mangrove forests in Guangdong province was opposite to that of patch quantity, the changes of patches were mainly expansion and fragmentation. When MPS change trend was consistent with the change trend of plaque number, the increase and decrease in the change of plaque were dominant. Information on annual mangrove area distribution and structural changes can provide more detailed data and reference for the rational development and protection of mangroves and support ecological restoration and finely tuned mangrove management.