Chair Professor, Department of Chemistry;
Director, State Key Laboratory of Marine Pollution;
Associate Dean (Research & Postgraduate Education), College of Science;
City University of Hong Kong
Reclamation and marine infrastructure projects often adopt simple artificial vertical or sloping seawalls as coastal defences against wave action, flooding and land erosion. However, these structures do not possess any microhabitats that can be readily occupied and used by marine organisms as refuges and feeding grounds. Through incorporating the knowledge of marine ecology and collaboration among ecologists, architects and engineers, we are able to design eco-friendly artificial structures to serve dual roles as coastal defences and functional ecosystems for enhancing marine biodiversity and ecosystem services such as carbon sequestration and biofiltration. In this presentation, I will introduce the basic ecological principles for eco-engineered shorelines and draw examples from different parts of the world. I will also highlight the results of several recent trials of eco-engineered shorelines in Hong Kong. The implementation of eco-engineered shorelines for restoring manmade habitats will support the national master plan of China for ecosystem restoration (2021-2035), and the United Nations Decade on Ecosystem Restoration (2021-2030).
Work Group Leader, Leibniz Centre for Tropical Marine Research (ZMT), Germany
Editor-in-Chief, Estuarine, Coastal and Shelf Science (ECSS)
The tropical island of Hainan is the largest special economic zone of China and its coasts were once lined with mangrove forests, seagrass meadows and coral reefs. The beauty of these coastal ecosystems founds their economic potential for tourism, which is a major and growing sector. However, activities in other major economic sectors, i.e. agriculture, aquaculture and urbanization/industrialization, affect and impair the integrity of the coastal ecosystems and hence their economic potential and related livelihoods of the population.
This vicious cycle started in the 1960s when mangroves were massively deforested and converted into aquaculture ponds on Hainan. Brackish water aquaculture, with intensive use of artificial fertilizers and feed was and is a major pillar of Hainan’s economy. Untreated wastewater including large amounts of anthropogenic nitrogen is either released into semi-enclosed coastal bays or directly into coastal back-reef areas where it leads to eutrophication. We traced the pathway of anthropogenic nitrogen from aquaculture ponds into coastal waters and sediments as well as into the food web over four trophic levels. Seagrasses are strongly impaired, abundance and diversity are declining, in some places they disappeared totally. Coral reefs are similarly affected by eutrophication, organic pollutants, overfishing and other threats. The connectivity of coastal ecosystems is disrupted and ecosystem service supply is diminished.
Long-term research in the inter- and transdisciplinary collaborative Sino-German projects LANCET, ECOLOC and TICAS enabled us to delineate causes and consequences of coastal development for ecosystem functioning, services and connectivity in Hainan’s coastal zone. We established a science – society interface and developed and implemented measures towards a more sustainable use of the coastal zone together with stakeholders from policy and civil society. Measures included awareness raising among all stakeholders through education events in schools, public talks, stakeholder workshops, radio interviews, art exhibitions and ‘citizen science’. Recommendations for decision-makers were published in a Policy Brief and training courses were conducted for aquaculture farmers. Finally, seagrass conservation and restoration projects led by transdisciplinary teams are in operation. Hainan stands as an example for problems related to coastal development observed around the globe, but also shows a way forward towards sustainability.
Professor
Tsinghua University, China
Hainan International Blue Carbon Research Center
Blue carbon is broadly considered as nature bases solution (NbS) for mitigating global climate change, which attracts increasing attentions from scientists, policy makers, carbon traders and even investors. Mangroves, salt marshes and seagrass beds are three major blue carbon ecosystems (i.e. coastal blue carbon ecosystems) with global coverages, and very high carbon density, ecosystem CO2 exchange rates, carbon burial rate and carbon sink potentials. Although great efforts have been made on scientific research, regulation policy and marketing of coastal blue carbon during last 15 years, there are still many knowledge gaps and issues regarding the mechanisms of coastal blue carbon sinks and their future dynamics, the protocols, standards and quantification methodologies for these valuable coastal wetland ecosystems, which hinges our understanding of blue carbon properties, incorporating blue carbon into national carbon trade system and value realization of blue carbon. Meanwhile, the mangroves, seagrass and salt marshes in China are still under significant pressures of human activities, biological invasion and global climate change, even most of them are under strict protections by state and local governmental regulations. Great investment will be placed on restoration of these coastal wetlands in next few years, providing great opportunities for coastal blue carbon research, monitoring, and trading. In this talk, we will summarize (1) Definitions of blue carbon including coastal blue carbon, (2) Progresses of coastal blue carbon research and monitoring, (3) Trends and issues of coastal blue carbon assessments and trading, and (4) future perspectives of coastal blue carbon research and applications.
Natural systems have been evolving for many of millions of years, elaborating complex relationships that suffuse and diversify modern day ecology. Using examples and case studies, this talk examines how complexity develops over time in mangrove systems. Genetic studies indicate mangrove species have diversified greatly over the last 100 million years, but have also suffered many extinctions due to sea level rise. The coming decades may offer an opportunity to observe rapid sea level rise on our warming planet, and possible new mangrove extinctions over the next 100-1000 years. Other time-based examples include how weekly and daily tidal variations can interact with groundwater to export nutrients and carbon from mangroves to the coastal ocean, while also supplying freshwater needed for tree growth. The most complex relationships in the mangrove systems probably involve food web interactions that are very flexible through time, and becoming easier to characterize with new isotope, trace element, lipid and eDNA technology. Also soil-based interactions between tree roots and colonizing fungi are being newly characterized through DNA assays, with an emerging perspective that fungi may control many time-based patterns of tree growth and mangrove forest development.
The talk concludes with a homework assignment: conference participants are asked to use online resources to create a 1-5 page e-scrapbook describing their experiences on the Day 3 Eco-Tour of local mangroves in Hong Kong. Along with cell phone photos and impressions recorded as text, the e-scrapbook should include mangrove ecosystem images from artificial intelligence as second opinions about what was observed. Homework for conference organizers is to archive the e-scrapbooks and make them available for future use; the e-scrapbooks may serve as reminders of what mangrove systems looked like in 2023 and baselines for judging subsequent mangrove complexity evolution or devolution in the Hong Kong area.
Professor and Director, Simon F S Li Marine Science Laboratory, School of Life Sciences
Director, Institute of Environment, Energy and Sustainability
The Chinese University of Hong Kong
Adjunct Professor
Griffith University, Australia
The structure and function of coastal wetlands are strongly dependent on intricate interactions of the biological community, e.g., the invertebrate assemblage, and the physical setting, e.g., the hydrological regime. These interactions result in the capacity of different coastal wetlands for delivering various ecosystem services to different extents. Decades of research on ecological processes have provided key knowledge on the interactions driving ecosystem function, which may be used to direct future management to maximize the capacity for specific services as well as optimize the balance of potentially competing demands for services. Using the service of blue carbon storage as example, I will demonstrate how decades of research on the carbon dynamics of mangrove forests may allow managers to harness the capacity of these ecosystems to contribute to emission mitigation, especially on tropical peri-urban coastlines.
Professor
Beibu Gulf University, China
Assistant Professor
School of Science and Technology, Hong Kong Metropolitan University, Hong Kong
The coastal ecosystems of Lung Mei and Ting Kok in the Tolo Harbour and Channel in Hong Kong are known for their high biodiversity. Unfortunately, the construction of an artificial beach in Lung Mei has threatened the ecological value of the region. This study was conducted to investigate the marine biodiversity of Lung Mei and Ting Kok after the beach was built. Two sites, Lung Mei East and Lung Mei West, and one reference site, Ting Kok East, were selected and monitored for a period of one year. Quantitative surveys were conducted twice during the dry and wet seasons, including transect and quadrat surveys, beach seining and purse seining. Additionally, monthly qualitative monitoring was carried out to supplement the species found at each site. A total of 327 marine species were recorded in the course of the study. Ting Kok East (TKE) was the most biodiverse site, with 243 species, followed by Lung Mei West (LMW) with 239 species, and Lung Mei East (LME) with 208 species. Within the Lung Mei sites, LMW had a higher species richness, abundance and biomass than LME. The dominant taxonomic groups were bivalves, gastropods, crustaceans, and fishes, which accounted for 74.3% of the total species recorded. Additionally, species richness, abundance, and biomass were higher during the summer than in the winter across the three sites. The higher biodiversity of benthic species in TKE compared to LMW and LME could be explained by the differences in the substrate and habitat composition. The more natural and diverse habitats in TKE may have contributed to its higher biodiversity, whereas the less natural and diverse habitats in LME may explain its lower biodiversity. This systematic assessment of biodiversity over the course of a year has allowed for a better understanding of coastal biodiversity in a post-construction scenario. The artificial and degraded shores at Lung Mei could be potentially restored by implementing ecologically engineered techniques to increase the provision of suitable habitats for marine species.
Postdoc
School of Science and Technology, Hong Kong Metropolitan University, Hong Kong
The periodic tidal cycles in mangroves ecosystem induce wide variation in environmental parameters across small spatial scale. These variations across intertidal locations and pneumatophore lead to the formation of characteristic microbial zones with varying community structure and function. With the purpose of studying microbial zonation, the Ting Kok mangrove in Hong Kong was partitioned into three different zones: mudflat (TK_MF), mangrove (TK_M) and pneumatophore associated sediments (TK_PSAM). The sediment samples from all the three microbial zones were processed for metagenomic DNA extraction followed by shotgun sequencing and metadata analysis. Proteobacteria and Bacteroidetes were the most dominant phyla in all the microhabitats followed by Firmicutes (in TK_MF_ and TK_M_) and cyanobacteria (in TK_PSAM). Archaeal distribution remained uniform across all three habitats with Thaumarchaeota as the most abundant phyla. Simultaneous analysis was performed to study functional zonation associated with crucial energy metabolic pathways (methane and nitrogen metabolism) in mangrove ecosystem. Relatively high proportion of genes associated with methanogenesis was observed in TK_MF_ and TK_M_ samples as compared to TK_PSAM. For nitrogen metabolism, the relative abundance of nitrogen fixation and denitrification pathway were high in TK_MF_ and TK_M_ samples whereas nitrate reduction pathway was high in TK_PSAM_. To the best of our knowledge, this is the first attempt to study prokaryotic zonation in intertidal location and pneumatophore using shotgun sequencing.
Conservation Education Manager
The Nature Conservancy, Hong Kong
Pak Nai, adjacent to Mai Po Inner Deep Bay Ramsar Site, is one of the ecological hotspots in Hong Kong. The mudflat of Pak Nai, where Kon Pak Stream meets Deep Bay, is home to a variety of species including Chinese horseshoe crabs (Tachypleus tridentatus), Mangrove horseshoe crabs (Carcinoscorpius rotundicauda), black-faced spoonbills (Platalea minor), seagrass (Halophila beccarii), Hong Kong oyster (Magallana hongkongensis) and many mudflat organisms. It is an estuarine area with mangrove, seagrass bed, bare soft shore and a large area of abandoned benthic oyster farms in the low tide areas of the mudflat that has high potential to be converted to oyster reef. Oyster reefs are the most endangered marine habitat on the planet, with an estimated 85% global loss.
Despite its ecological importance, Pak Nai is currently not protected and under a multitude of increasing threats. To address this, The Nature Conservancy (TNC) has adopted the community conservation approach by working with local villagers and community partners to actively manage the coastal ecosystem in Pak Nai, since 2021 summer. TNC's work includes conducting scientific research, carrying out site-based habitat management, promoting responsible tourism, and raising public awareness. Over the past 1.5 years, TNC has engaged more than 3,500 members of public to reconfigure more than 5000m2 of abandoned oyster reef, removed more than 1200m2 of invasive cordgrass (Sporobolus alterniflorus), cleaned about 190m3 of aquaculture debris and 4,278kg of marine litter, in Pak Nai.
In this interim stage of our 3-year plan, TNC would like to share our latest progress and findings on managing different habitats in Pak Nai as well as the importance of adopting the community conservation approach.
Professor
Xiamen University, China
The human-created greenhouse gas emissions have caused dramatic changes in the earth's climate with warming and sea-level rise. Mangroves are recognized as a key potential and self-sustaining Nature-based solution (NbS) to mitigating climate change attributed to their ability to capture and store carbon. High photosynthetic rates, fast sediment deposition rates, and low decomposition in anoxia sediment with coastal flooding contribute to high carbon capture and storage in mangroves. Fast sediment accretion rates will help build up land to balance the rising sea level. Due to the conservative water use characteristics, mangroves can furthermore contribute to the coastal water cycle and alleviate freshwater shortages. Importantly, mangrove ecosystems conserve high biodiversity and maintain a livelihood in coastal regions, if they are healthy and sustainably managed. However, mangroves are facing the challenges of global climate change and land-use changes. Whether they can serve well as NbS to mitigate climate change depends on their capacities for ecosystem-based adaptation, especially on the adaptations of plant communities. A robust consideration of global change factors and their interactions with mangroves will help us better predict of the future patterns and functions of this ecosystem. Increased knowledge of the combined effects between climate factors (e.g. elevated atmospheric CO2 concentrations, warming, sea-level rise) and local environmental factors (e.g. hydrology, flooding, nutrient enrichment, species competition, etc.) would reduce uncertainty in the impacts of climate change with varying anthropogenic stressors. Research-integrated fundamental knowledge will broaden the community of practice of blue carbon science, and contribute to the management and new economic pathways to support carbon-neutral strategies.
Research Fellow
Third Institute of Oceanography, China
Coming soon.
Associate Professor
Member of State Key Laboratory of Marine Pollution
City University of Hong Kong, Hong Kong
There are four extant horseshoe crab species, with two of them, Tachypleus tridentatus and Carcinoscorpius rotundicauda, being found in Hong Kong. Owing to human exploitation for consumption and biomedical use, pollution and coastal development, horseshoe crabs are facing with extinction risk and T. tridentatus, the largest among the extant species, was categorized as endangered in the IUCN red list 2019.
The highest density of T. tridentatus in Hong Kong was found on two neighbouring mudflats, Ha Pak Nai and Pak Nai, in Deep Bay. Although the physical environment, including shore profile and sediment organic content of these sites, were similar, Pak Nai had a higher percentage of area covered with oyster rubbles from abandoned oyster farms than Ha Pak Nai because the frequency of beach cleanup organized by green groups in the former was only 1/3 that of the latter.
Horseshoe crabs avoid habitats with a high density of rubbles which affects their foraging behaviour, resulting in a more convoluted foraging trail. Ha Pak Nai is a more favourable habitat for horseshoe crabs, as reflected by a higher population density, a larger median prosomal width, and a higher median wet weight. After correcting for the size difference, individuals T. tridentatus in Hai Pak Nai were 20% heavier than those in Pak Nai. Therefore, regular beach cleanup is an effective way to improve the habitat quality for horseshoe crabs and should be promoted as a conservation strategy for these “living fossils”.
Research Assistant
Hong Kong Marine Ecological Association, Hong Kong
Coastal wetlands, such as mangroves, mud flats and sandy beaches, are often key nursery grounds for marine fishes. These habitats are also important not only in supporting a rich biodiversity, but also in social-economic aspects as they provide various ecosystem services and fishery resources to local communities. Tolo Harbour and Channel (the Tolo Area) at north-eastern Hong Kong in South China harbours various coastal wetlands including the fourth largest mangrove stand in Hong Kong. The Tolo Area has been previously recognised as a nursery ground of marine fish species, including those that are commercially important. However, these coastal wetlands, and the marine biodiversity and fisheries resources in this area have been jeopardised by various anthropogenic threats such as coastal development and pollution. This study aimed at providing up-to-date ecological information of juvenile marine fishes in the Tolo Area, and identifying locations with a high conservation priority. A three-year study, using beach and purse seining, was carried out to assess the current status of the juvenile fish community in coastal soft-bottom and shallow water habitats throughout the Tolo Area. A total of 171 species/taxa were recorded, including the IUCN-red-listed vulnerable species of seahorse Hippocampus kuda. Juvenile individuals were found in 155 of the recorded species/taxa. Juvenile fishes were dominated by small and/or fast-growing species. Significant spatial and seasonal variations in juvenile fish assemblages were recorded in the Tolo Area. Diel differences in juvenile fish assemblages were also recorded in sites where additional night-time surveys were conducted. Species richness was generally higher in outer Tolo Harbour and inner Tolo Channel, and priority should be given to the coastal soft-bottom and shallow water habitats in these areas to protect the species diversity and fishery resources. The results of this systematic study provide an ecological baseline of juvenile fishes in the Tolo Area for future monitoring and conservation of the coastal wetlands marine fish communities.
Postdoctoral Research Associate
The Hong Kong University of Science and Technology, Hong Kong
What is an ecosystem service? Often not well defined even among those who employ the term often, this seminar presents a conceptual framework for understanding ecosystem services that facilitates their assessment and valuation. Produced from a combination of spatial econometric and GIS modelling methods, results from a case study of mangrove plantations in Bangladesh are used to demonstrate this approach for both provisioning and regulating ecosystem services. Results from a household survey across eight coastal villages illustrate how and who among local rural communities utilize these resources. The predominant direct use of the mangrove plantations within local rural communities is the extraction of detritus and non-main stem material (e.g., limbs, leaves) for combustible fuel, disproportionately by the landless and the poor. This study uses household foraging distances to estimate and map net value densities based on reported market prices of extracted goods. Cost-benefit analyses suggest that direct use values alone have justified the establishment and management of previously planted stands. However, other indirect values must be taken into account if these areas are to merit additional plantations. Analysis of GIS data on coastal dynamics and land cover demonstrate the effectiveness of mangrove plantations for facilitating accretion and preventing erosion in Bangladesh. The results indicate that plantation areas experience greater rates of accretion relative to erosion than non-plantation areas. On the other hand, econometric analyses fail to show any benefits of the mangrove plantations from acting as barriers to tropical cyclone activity. Thus, rigorous, data-driven assessment can yield counterintuitive results, which underscores the need for primary data collection in the assessment and evaluation of ecosystem services.
Refocusing on Hong Kong, what key ecosystem services from mangroves and other wetlands are relevant to our urban setting? What methods are appropriate for evaluating them? Prevailing studies of ecosystem services in Hong Kong and the Greater Bay Area have relied upon questionable benefit transfer methods that lack external validity. One possible alternative is the application of local primary data in allometric models. Given the paucity of primary data currently available, this remains a challenging information gap for Hong Kong.
Research Associate
Beibu Gulf University, China
Heavy metals (Ni, Cu, Cr, Zn, Pb, and Cd) are persistent widespread pollutants in different environmental compartments. In this study, the chemical speciation of heavy metals was studied in surface sediments of the Cross River Estuary (CRE) and surrounding environment, Gulf of Guinea, South East Nigeria. In addition, the sources of sedimentary organic carbon (OC) were quantified using a Monte Carlo mixing model utilizing the stable isotope of OC (δ13C) and the molar ratio of OC to total nitrogen (OC/TN) as source markers for organic matter derived from terrestrial soil, mangrove wetland, and marine phytoplankton to determine their influence on heavy metals sources in estuarine sediments. A Bayesian Network (BN) model was developed to study the interdependency of heavy metals on factors such as sedimentary OC sources, TN, pH, salinity, and sediment grain sizes. Chemical speciation results showed that Pb, Cd, Zn, and Cr were predominantly available in non-residual phases, suggesting their potential bioavailability. Cd was the most polluted heavy metal with the highest bioavailability risk in the study area. According to the BN model results, sedimentary OC from mangrove wetlands played a key influencing role on the contents and variability of Pb and Zn, while the input of OC from terrestrial soil strongly influenced Cu and Ni contents. In the estuarine sediments, Cd and Cr were sensitive to changes in sediment pH, while Ni was sensitive to salinity variation. Strong interdependency between Cd and TN suggested that nitrogen has the potential to increase Cd bioavailability upon release from sediments. This study indicated that the ecological health of coastal marine systems can be significantly impacted adversely when the surrounding wetland environments are degraded and, at the same time, significantly perturbed by human activities. Overall, this study highlights the need for coastal wetland protection,
conservation, and restoration.
Assistant Professor
The University of Hong Kong, Hong Kong
Seagrass, mangroves and saltmarshes are important ecosystem engineers with fundamental ecological roles in coastal areas. These plants mitigate habitat erosion, they help to tackle climate change through carbon removal and storage, they provide shelter and food to many animals, and they also improve water quality by filtering out nutrients and by controlling pathogens. These ecosystem services contribute with numerous socio-economic benefits to the coastal communities, sustaining for instance many commercial fisheries and aquaculture activities. Despite of these valuable and fundamental services, we are witnessing a significant and rapid decline of natural populations of coastal marine plants in Hong Kong. Such declines are mainly driven by anthropogenic pressures, including pollution and the alteration of the seascape configuration. As a consequence, the ecological connectivity of coastal marine vegetation has been strongly affected, generating important functional effects on the health and resilience of coastal wetlands. Here, I will discuss the outcomes of ongoing projects enhancing wetland ecosystem services by restoring the connectivity between seagrasses, mangroves and saltmarshes in Hong Kong. Using an environmental DNA (eDNA) approach, we identified higher biodiversity assemblages in areas where seagrass connectivity was considered as part of the restoration intervention, compared to areas in which seagrasses were restored in isolation. The result of this work highlights the importance of landscape/seascape connectivity when planning restoration and managing efforts for coastal vegetation in highly urbanized and fragmented zones.
Postdoc
The University of Hong Kong, Hong Kong
Often situated on populous tropical coasts, mangroves are commonly threatened by anthropogenic nutrient enrichment. Sesarmid crabs play an essential role in mangrove ecosystem processes, mainly attributed to their leaf-eating habit. This study investigated how mangrove sesarmid crabs respond to nitrogen (N) enrichment and their regulatory role in nutrient dynamics. We hypothesized that N enrichment would change the microphytobenthos (MPB) communities in surface sediment, which may modify the crab's diet, e.g., increased use of MPB and reduced leaf litter consumption, thus affecting their role in nutrient dynamics through shaping the microbial communities in surface sediment. The same amount of 13C-enriched mangrove leaves added to tidal mesocosms with two factors and four treatments (high/low N enrichment and presence/absence of crabs) each day for two months. Field levels of N, crab and MPB abundances were measured as reference. N enrichment at 2x and 20x the background level resulted in significant changes in the MPB composition (increased relative abundance of cyanobacteria). Stable isotope analysis followed by mixing models suggested that the main carbon source of crabs shifted from leaf litter to cyanobacteria in mesocosms for both high (20x) and low (2x) N enrichment. However, their leaf-eating habit (leaf consumption rate) did not change during the experiment. The significantly lower total cellulase activity of mesocosm crabs compared to field crabs might explain the decreased C assimilation from leaf litter. In the mesocosms with crabs, microbiome taxonomic and functional structure showed significant differences between high and low N enrichment, driving significantly higher C processing rate in mesocosms with high N enrichment. This demonstrated linkage between nutrient dynamics (through stable isotope analysis) and the composition of microbial communities provides a framework for achieving mechanistic insights into how sesarmid crabs drive key biogeochemical processes in mangroves under eutrophic conditions.
MCF Mangrove Foundation, China
Ramsar Convention on Wetlands has highlighted the importance to recognize, maintain, restore and wisely use the vital ecosystem functions and the ecosystem services they provide to people and nature. CEPA program has been developing in China since 1992, and has gone through various stages. Multiple challenges for promoting wetland education in China are identified. For instance, lack of professional exchange and practice, disconnection between wetland nature reserves and formal education, as well as low awareness of public on wetland and migratory birds conservation.
One of the key solutions proposed is the China Wetland Centers (CWC) Initiative established in 2022 at the Ramsar Convention COP14. It aims to connect people and wetlands and promote public engagement in wetland conservation through the development of wetland centers across the country. Its key objectives are to contribute to action plan for the development of wetland centers, capacity building for various stakeholders, platform for exchange and communication, and model wetland centers.
As a keen wetland education group, MCF has established several wetland centers including Shenzhen Bay center. We also developed mangrove education program which integrates with formal education curriculum. Until end of 2022, there were 6,421 students from 133 classes which have participated in the Shenzhen Bay wetland school education program.
In 2020, with help from professional experts, MCF conducted evaluation of the teaching outcomes. It was found that the program has significantly helped students with environmental learning, social communication and academic performance. Capacity building for school teachers and nature reserve education staff was also conducted through training and providing guidebooks.
Looking into future, the enhancement on exchange and collaboration among national and international networks, CEPA curriculum for formal education, as well as outreach in public communication are essential for ensuring the society's recognition on importance of wetland conservation.
Associate Professor
Universiti Sains Malaysia, Malaysia
The impact of human activities on biodiversity loss in Southeast Asia is a pressing issue that requires attention. This study aimed to assess the extent to which human activities are contributing to the loss of biodiversity in Southeast Asia. To achieve this objective, a comprehensive review of the available literature and analyzed data from various sources was conducted and the analysis revealed that human activities, such as deforestation, land-use change, poaching, and pollution, have led to a significant decline in biodiversity in Southeast Asia. For instance, Southeast Asia is home to 15% of the world’s plant species, and 70% of the region’s forests have been lost or degraded due to human activities. Additionally, overexploitation of marine resources and habitat destruction have caused the decline of several marine species, including sharks and sea turtles. Significant negative correlation between human activities and biodiversity was noted. Based on our findings, if current human impact on biodiversity continues, it is projected that Southeast Asia could lose up to 45% of its biodiversity by 2050. This projection highlights the urgency of addressing the impact of human activities on biodiversity loss in Southeast Asia. This study provides important insights into the impact of human activities on biodiversity loss in Southeast Asia. The findings underscore the need for effective conservation strategies to protect the region’s rich biodiversity. The implementation of policies to reduce deforestation, regulate land-use change, and address overexploitation of marine resources is essential to ensure the long-term survival of Southeast Asia’s biodiversity.
Associate Professor
Beibu Gulf University, China
Mangrove is a typical natural landscape with great ecological, social and economic functions and values, and should be highly valued and protected. However, in the past few decades, mangrove resources have suffered serious damage. Chinese mangroves, as an important part of the global mangroves, are of great research value. In the present study, the status and challenges of Chinese mangrove resources in Guangxi were investigated. In terms of administrative region, mangroves in China mainly occur in three provinces, Guangdong (9,891ha), Guangxi (8,375ha), and Hainan (3,930.3ha), constituting an area of 22,196ha. Guangxi coast of Beibu Gulf (8,375ha), making up 35.72 % of China mangroves. Mangrove area in the three regions constitutes 78.66% of total mangrove coverage in China. In this study, the community types and spatial distribution of mangroves along Guangxi coast was studies based on multi-source high-resolution satellite imageries, using image processing, GIS, GPS technology and field investigations. As per results, there were 7 243.15 hm2 of mangroves in Guangxi in 2023. Totally, 2793 mangrove patches were found, with the average patch-area of 2.59 hm2. The total area and the number of patches of mangrove in Beihai city were 3263.66 hm2 and 905 respectively, accounting for 45.06% of mangroves in Guangxi. There were 2097.41 hm2 in Qinzhou city, which had 1259 patches and accounted for 28.96% of mangroves in Guangxi. Fangchenggang city had the smallest area of mangroves among the three coastal cities in Guangxi, with 1882.08 hm2 in area, 629 patches which accounting for 25.98% of mangroves in Guangxi. Twenty-one types of mangrove communities in Guangxi were identified, including Community Avicennia marina, Community Avicennia marina+Aegiceras corniculatum, Community Aegiceras corniculatum, Community Aegiceras corniculatum+Avicennia marina, and Community Bruguiera gymnoihiza –Avicennia marina, etc. and were among the most dominant mangrove communities. At the same time Guangxi mangrove resource faces serval challenges, for instance, the development of Beibu Gulf Economic Zone threatens the mangrove ecosystems. Seawall construction, shrimp pond enclosures, and mangrove cutting degrade mangrove habitats, leading to mangrove damage and death. Identifying suitable mangrove restoration sites and determining suitable habitat conditions are key factors that affect the success of mangrove restoration.
Professor
Deputy Dean, College of Marine Sciences
Beibu Gulf University, China
Asian horseshoe crabs are ancient marine arthropods inhabiting coastal and estuarine ecosystems along the west coast of the Pacific Oceans. The distribution of mangrove and horseshoe crab habitats along the Chinese coastline is highly overlapped. However, the role of mangrove wetlands in supporting horseshoe crab populations is largely unknown. Field investigations in northern Beibu Gulf, China found that, Asian horseshoe crab nests were distributed in bare flats in between mangrove patches, at the bases of mangrove roots, or near tidal creeks adjacent to seawall. Nests can also be found near man-made structures, including mangrove boardwalks, seawall slopes, water control gates. These areas were characterized with elevated, mildly sloping substratum within the high tide zones. For the nursery habitats, juvenile Asian horseshoe crabs are primarily distributed on upper intertidal flats outside the mangrove fringes or saltmarsh patches close to tidal creek outflows. The relative locations of their spawning and nursery habitats suggest that mangrove tidal creek may be the main route for horseshoe crab larval dispersal. Based on the present findings, effective management measures for conservation of Asian horseshoe crab populations include: (1) routinely remove ground cages/erected stick nets and abandoned aquaculture farm structures/rubbles within upper intertidal areas, particularly during peaked breeding and nursery seasons (May-July), (2) regulate artisanal aquaculture, fishing and beachcombing activities near mangrove fringes and along tidal creeks, (3) avoid coastal projects that alter the beach topography and bathymetry, (4) create mounds with suitable slope and sediment textures along the shoreline to improve spawning habitats.
Associate Professor
The Chinese University of Hong Kong, Hong Kong
Coastal
mangroves are considered to be important carbon sinks due to their high primary
productivity and carbon burial rates. Yet, there is currently a paucity of
studies measuring the fluxes of carbon dioxide in mangrove ecosystems at high
temporal resolutions. Moreover, the biosphere-atmosphere exchange of other
greenhouse gases, e.g. methane, between mangroves and the atmosphere is not
well characterized by continuous field measurement. In this presentation, we will
present the results of our work on long-term monitoring of carbon dioxide and
methane fluxes in a subtropical estuarine mangrove in Hong Kong. Our findings
suggest that estuarine mangroves are a net sink of carbon dioxide but a net
source of methane. The warming impact arising from methane emissions could
offset over 50% of the cooling impact generated by carbon dioxide uptake by
estuarine mangroves. Future climate change could further reduce the strength of
mangrove wetlands as a nature-based climate solution through the effects on
greenhouse gas fluxes.
Education Director
WWF-Hong Kong
The latest edition of “Living Planet Report 2022” concluded that globally, there has been an average decline of 69% in wildlife species populations since 1970, implying the planet is in the midst of a biodiversity and climate crisis, and we have a last chance to act.
With the journey began in 1961, WWF is now active in nearly 100 countries with a mission to build a future in which humans live in harmony with nature. As the world's leading conservation organization, we works at every level. Through collaborating with people around world, WWF strives to bend the curve of nature loss hence people and nature can thrive!
WWF-Hong Kong is an integral part of the WWF global network since 1981. Our work here began with managing the Mai Po Nature Reserve, an important part of the only Wetland of International Importance (Ramsar Site) in Hong Kong SAR. We have since expanded our mission to cover other aspects of conservation and sustainability with the goal to transform Hong Kong into Asia's most sustainable city. To achieve this, it is dependent on all people from across the community.
Engaging all walks of life to become part of the conservation solutions are done through various community education and eco-programmes. WWF-Hong Kong is operating the nature centre at Mai Po Nature Reserve to help create a new generation of conservation and sustainability advocates through fun, engagement and real-life experiences. The conservation management at the wetlands of Mai Po is a good model to demonstrate how the communities in Hong Kong can be engaged, motivated and mobilized to support nature conservation.
“Change the way we live” and “Habits Protect Habitats” has become the mantras for WWF's education works. Let's join hands to create a nature-positive future.
Postdoctoral Researcher
Stockholm University, Sweden
Visual surveys are commonly used to quantify and characterize beach litter. However, they can be time-consuming and challenging to conduct on remote or inaccessible beaches. To address this issue, we propose an alternative approach for assessing beach litter using an unmanned aerial vehicle (UAV) or drone equipped with automated image acquisition and processing capabilities. We conducted a study by randomly placing litter of varying sizes, colors, and materials on two beaches with different substrates. Using the drone, we captured images of the beaches at various operating heights and lighting conditions, and untrained personnel identified the litter in the photos. We are currently undertaking a comprehensive survey using drone to quantify beach litter in Hong Kong. In the future, we believe that the integration of machine learning will further enhance the survey’s efficiency by automating the object identification process. Our findings suggest that drones can be a cost-effective and efficient sampling method for routine beach litter monitoring programs.
Citizen science (i.e. the involvement of non-scientists in scientific research) has been shown in recent years to combine the possibility to expand the collection of valuable scientific data while simultaneously engaging local communities to better understand and manage local ecosystems. Nowhere is this more important than in the management of transitional wetlands, ecosystems that provide a range of services to multiple stakeholders and are severely threatened across the globe.
There is increasing interest in harnessing the scientific, social, economic, environmental, and political benefits of citizen science by using it within environmental monitoring schemes. Here, we explore the opportunities for combining citizen science and water quality monitoring data in wetland and river ecosystems. One example is the monitoring and management of multiuse wetlands in the Yangtze and Pearl river catchments, where wetlands are managed for agricultural, tourism and biodiversity purposes, but whose ecosystem services are poorly defined, largely due to limited data. The second is the Rokel River ecosystem in Sierra Leone, which has multiple stressors and yet provides major services to a population of over 2 million people.
In both cases, the creation of a citizen science programme to engage communities and local persons was shown to provide important data for wetland management. In the Nansha and Tianfu wetlands, citizen scientist data indicated that agricultural conversion of natural areas had important impacts of wetland nutrient and carbon removal services. In the Rokel River, citizen scientists are participating directly in an integrated basin management plan, providing key data and knowledge to the management process.
Research Assistant
Xiamen University, China
Coastal wetlands have a variety of ecosystem services including blue carbon sinks and biodiversity conservation. As an important component of nature-based solutions (NbS), coastal wetlands sequestrate blue carbon and mitigate climate change. The blue carbon projects (BCPs) that generate carbon credits for the market by conserving and restoring coastal wetlands act as an effective way to realize the value of coastal wetlands, which play an important roles of blue carbon ecosystems in coping with climate change. This study overview the existing carbon market and carbon market methodologies applicable to BCPs in the global, and analyses the development of BCPs in the current carbon market. Currently, totally 12 BCPs, all of which are mangrove projects, have been registered under Clean Development Mechanism (CDM), Verified Carbon Standard (VCS) and Plan Vivo Standard. Methodologies for mangrove BCPs in mainland China have also been developed, and mangrove BCPs in Fujian and Hainan Province have been successfully developed and traded. However, the methodologies applied to the BCPs is still limited, which need to be developed and promoted across a wider range of project types and ecosystems. In addition, we discussed the strengths and challenges of implementing BCPs and compared the management strategies used in global BCPs to provide advice on future BCPs design as well as blue carbon market development. BCPs can not only provide carbon credits for the market, but also enable community development and biodiversity conservation. And political support, effective community engagement and numerous goals in addition to the generation of carbon credits are critical for project success.
Manager, Wetland Research
WWF-Hong Kong, Hong Kong
Eurasian otter (Lutra lutra) is threatened in China and a small population is known to persist in and around Mai Po Nature Reserve. As a nocturnal species that is elusive with a large home range, studying otter is often a challenge and insufficient data on the demography, spatial ecology and threats of the species hampers the development of effective conservation measures. WWF-Hong Kong is currently working with a multi-faceted approach in order to collect more scientific information about the population and space use of otters through collaboration, engagement and public education.
With generous donation from Hongkong Bank Foundation, WWF-Hong Kong has launched the “Wetland Incubator” project in 2021 to find solutions to improve the city's resilience towards climate and ecological change. As the backbone of scientific research, WWF-Hong Kong is collaborating with Kadoorie Farm and Botanic Garden to study otter population and distribution in and around Mai Po Nature Reserve via camera trapping, regular sign survey and genetic analysis. General public has also been trained as citizen scientists to support otter surveys. With the help of Wildlife Insights – a web-based camera trap data management platform, citizen scientists are able to assess camera-trapped photos at home, amid the pandemic. To further enhance otter sign detection, innovative ideas have been incubated and this include trial of spraint detection dog by engaging local dog trainer and design of otter platform by local secondary school students. A series of public awareness-raising activities focusing on Eurasian Otters have also been designed and developed by our recruited education design teams facilitated by WWF-Hong Kong.
The value of multi-faceted approach lies on the integration of knowledge and strength of different stakeholders in solving the challenges we face. This provides opportunities to not only broaden our knowledge on the species, but also implement ideas that a single party may not be able to achieve and allow more people to understand the conservation issue. In face of development pressure and threats to the otters, engaging different parties together to understand and contribute would bring us closer to achieving holistic management of a landscape where otters and people strive.
Professor
Southern Marine Science and Engineering, Guangdong Laboratory, Guangzhou, China
Coastal wetlands trap plastics from terrestrial and marine sources, but the stocks of plastics and their impacts on coastal wetlands are poorly known. We evaluated the stocks, fate, and biological and biogeochemical effects of plastics in coastal wetlands with plastic abundance data from 112 studies. The representative abundance of plastics that occurs in coastal wetland sediments and is ingested by marine animals reaches 156.7 and 98.3 items kg−1, respectively, 200 times higher than that (0.43 items kg−1) in the water column. Plastics are more abundant in mangrove forests and tidal marshes than in tidal flats and seagrass meadows. The variation in plastic abundance is related to climatic and geographic zones, seasons, and population density or plastic waste management. The abundance of plastics ingested by pelagic and demersal fish increases with fish length and dry weight. The dominant characteristics of plastics ingested by marine animals are correlated with those found in coastal wetland sediments. Microplastics exert negative effects on biota abundance and mangrove survival but positive effects on sediment nutrients, leaf drop, and carbon emission. We highlight that plastic pollution is widespread in coastal wetlands and actions are urged to include microplastics in ecosystem health and degradation assessment.
Research Scholar
Bharathiar University, India
Coastal wetlands are the one of the most disappearing habitat among all the wetland types. Landfilling, construction of buildings, urban development projects, aquaculture farming are some of the major threats to this wetland. The study focused on the less studied and unexplored coastal wetland system in northern Kerala, India. Kavvayi, Azheekkal, Dharmadam, Ezhimala, Valapattanam are the selected estuaries for this study. Azheekkal, Madakkara, Ezhimala, Dharmadam, valapattanam are the major estuaries in Kannur and kasargod district, Kerala state India. The area is part of Western Ghats. All these estuaries ultimately join with Arabian Sea. As a part of the research fish diversity and its availability in each coastal wetland were studied from monsoon to summer season. The diversity and the availability of the fishes were collected from the estuarine landing centers .landing survey was systematically conducted in all season to know the fishery resource of each estuary. Presence of 158 fish species were recorded. There are 28 elasmobranches were present throughout the study area. Fish diversity and species richness was abundant in Dharmadam, Azheekkal and valapattanam. Fish diversity and richness was calculated by PAST software. A community platform we made for the open interaction for the fisherman community in each estuarine zone. There are 580 active Fisherman were interviewed to know the perception on fish and fishery in the estuarine habitat. The unsustainable fishing or Juvenile catch was high during monsoon. Here the study focused only on finfishes and elasmobranches (Rays &sharks).The salinity in each estuary was recorded through the onsite salinometer in every regular interval. The community participation and socially committed fisherman youth wings help to record the water parameter data. We already provide one day training for the fisherman community for conservation and sustainable use of fish and fishery in all six estuaries. Interview, survey, focal group discussion, estuary wise vulnerability assessment were conducted. To ensure proper conservation of estuaries are essential for conserve fish, their habitat as well as livelihood of local fisherman community.
Assistant Professor
Guilin University of Technology, China
China’s coastal wetlands have been under considerable stress and have been severely damaged due to intense urbanization, climate change, sea level rise, marine disaster, land reclamation activities, natural hazards and pollution. Coastal wetlands in China are mainly distributed in coastal areas within nine provinces and cover an area of 5795 900 ha. Coastal areas have paid a high environmental price, especially with tremendous demand for land resources leading to a sharp decline in coastal wetland areas. By 2013, the wetland area occupied by infrastructural constructions had reached 1292 800 ha, an increase of more than 10 times compared with ten years prior. China has become the world’s second-largest economy, and GDP from coastal regions accounts for ~60% of China’s total. Thus, the restoration and reclamation of costal area is very essential. Coastal reclamation has occurred rapidly in China since the 1950s, with over 30% of tidal land reclaimed by the 1990s. Mangroves found in southern wetlands along the coastlines for which government initiated several project for its restoration in Zhejiang, Fujian, Guangdong, Guangxi and Hainan, consequently the mangrove area in China has increased from 14877 ha in 1997 to 23 081.5 ha in 2008. For the initial restoration, some invasive species were introduced which improved the wetland ecosystem services and structure. Other restoration practices includes, to solve the sediment shortage in habitat restoration, necessary to restore migratory waterbird numbers. Three other solutions were adopted for the rehabilitation wetland sites, including promoting sediment deposition and settlement through engineering intervention in Chongming Dongtan and Eastern Nanhui, and using dredged sediments to nourish and create new habitats in Hengsha Eastern Shoal. Along with the increase of wetlands and habitats, the abundance of waterbirds increased 1.3 times, 121 times and 1.5 times in these areas respectively. Other national level initiative are “the national Clean Bohai Sea Program”, the first regional ocean governance program in China, “polluters-pay” policy for pollution control and coastal environmental protection and Laws regulating water, environmental protection, and marine environmental protection have been issued during the last decade, which has helped in the reclamation of wetland areas.
Co-Chair, IUCN SSC Horseshoe Crab Specialist Group
Baseline Editor, Marine Pollution Bulletin
Distinguish Professor (retired), Hong Kong Metropolitan University
Associate Professor (retired), City University of Hong Kong
Horseshoe crabs are regarded as marine living fossil and their distribution is only confined to the east coast of USA to the Yucátan Peninsula of Mexico and along the coastline of some countries in Asia. Of the four extant horseshoe crab species in the world, three are found in Asia. In particular, the mangrove horseshoe crab (Carcinoscorpius rotundicauda) is closely associated with the soft sediment on the fringe of mangrove systems. This presentation provides an overview of the importance of horseshoe crabs in marine coastal ecology, the imminent threats of their population decline, and how conservation of coastal wetland can help safeguard their well-being, especially for the mangrove horseshoe crabs. The ongoing work of the Horseshoe Crab Specialist Group under the IUCN Species Survival Commission is also highlighted.
Senior Lecturer
Institute of Science and Environment, University of St. Joseph, Macao
Mangrove forests are vital coastal wetland ecosystems that provide various ecosystem services. In Macao, a city located on the west shore of the Pearl River in southern China, mangroves have become a focus of our scientific investigation. Our research has centered on the local mangroves, particularly investigating their role as nature-based solutions for addressing coastal water pollution and climate change-related issues. Moreover, they have the potential as carbon sinks and natural coastal barriers, which are crucial in mitigating the adverse effects of climate change. Our findings suggest that mangroves have an essential role to play in Macao's local environment. They are, however, vulnerable to threats due to rapid development in the city. To raise awareness about the value of mangroves, we have developed environmental awareness campaigns that aim to translate our research findings into actionable solutions. Through these initiatives, we have engaged thousands of students and other people from the local community in successfully implementing these activities. Overall, our research highlights the potential of mangroves as nature-based solutions for addressing environmental challenges and the importance of raising awareness to protect and conserve these ecosystems in Macao.
Post-doctoral Fellow
The Chinese University of Hong Kong
Coastal wetlands such as mangroves and salt marshes are termed “blue carbon” ecosystem due to their strong capacity for carbon (C) storage and sequestration. Unfortunately, many coastal wetlands have been intensively developed by land-use and land-cover change (LULCC) for more than a century owing to the rising population and subsequent economic growth. The impact of LULCC on ecosystem carbon dynamics has been previously documented at local scales or global scales, but uncertainty persists for the coastal wetlands due to geographical variability and field data limitations. Here, field-based assessments of plant and soil C contents and stocks of various LULCC types were conducted on nine regions along the coastline of China, ranging from temperate to tropical climate zones. These regions are cover natural coastal wetlands (including salt marshes and mangroves) and former wetlands converted to different LULCC types, including reclaimed wetlands, dry farmlands, paddy fields and aquaculture ponds. A total of 120 plant samples and 540 soil samples (top 30 cm) were collected in July to August 2020, for the measurement of content and stock of soil total and organic C, and plant biomass C. The results showed that natural coastal wetland had highest ecosystem organic C stock (EOC, sum of plant and soil organic C stocks) of 77.0±24.8 Mg ha-1, while LULCC generally decreased C contents and stocks of plant‒soil system by 29.6%±2.5% and 40.4%±9.2%, respectively, but significantly increased the proportion of labile C in soil. Conversion to aquaculture ponds caused largest EOC loss, following reclaimed wetlands, dry farmlands and paddy fields. The proportion of labile C in soil organic carbon can be an indicator reflecting the potential of organic C loss following LULCC. Our results showed that the response of plant-soil organic C to LULCC was mainly related to differences in soil particle size, soil water content, plant biomass, ratio of labile C to soil organic C, and NH4+-N concentration. Our results emphasize the importance of LULCC in triggering C loss in natural coastal wetlands, giving a hint that the current land-based climate models and climate mitigation policies must account for situation of specific land use types.
Associate Research Fellow
Guangxi Academy of Sciences, China
Bycatch is a severe challenge to global marine biodiversity conservation. Although studies have focused on bycatch of marine megafauna, research on relevant issues regarding invertebrates is limited, especially for the threatened horseshoe crabs. In this study, we explored the spatial pattern of common fishing gears and evaluated the bycatch intensity of two Asian horseshoe crab species in the intertidal zones of the northern Beibu Gulf, Guangxi, where the most abundant juvenile horseshoe crab populations distribute in along the coastline of China. Seven intertidal habitats for Tachypleus tridentatus and Carcinoscorpius rotundicauda were surveyed in the summer. A transect that crossed the tidal creeks and tidal flats between the high tide embankment/vegetation and low tide line of a given habitat was surveyed during the ebb tide. The type, number, and GPS of fishing gears were recorded when sighted; the bycatch number of each horseshoe crab species was counted and prosomal width of every bycaught individuals was measured. Bycatch intensities differed among the habitats, ranging 0.3-18.4 and 1.2-22.7 individuals per kilometer of transect for T. tridentatus and C. rotundicauda, respectively. Among the three types of fishing gears, ground cages and stick net sets which were located near the tidal creeks, fringes of mangrove forests, and low tide lines, caused a stronger bycatch pressure on these two species. Most bycaught horseshoe crabs were large individuals in late juvenile and adult stages. We suggest regulating the use of ground cages and stick net sets in the intertidal zones to reduce the stress of bycatch on threatened horseshoe crab populations. Ground cages and stick net sets should be regularly removed from focal areas, including tidal creeks, mangrove fringes, and low tide lines to ensure functionality of the intertidal zone as the spawning corridor and nursery habitat for these two species of Asian horseshoe crabs.
Guangdong Neilingding Futian National Nature Reserve
Shenzhen Bay (Deep Bay) is a coastal wetland located between Shenzhen and Hong Kong, and is a wintering ground and transit station for Nearly 100,000 waterfowls on the East Asia-Australia flyway, which has important ecological and social values. The Futian Mangrove wetland on the Shenzhen side is the only national nature reserve in the urban hinterland in China, and is more affected by urban development. This presentation focuses on the experience and practices of conservation and restoration work carried out on the Futian side over the past 30 years, systematically and rigidly protecting and restoring mangrove forests and waterfowl habitats, while taking into account the needs of Cityscape and Public visit. These experiences and practices will hopefully provide practical examples to other countries and regions in the urbanization process, helping to achieve the harmonious coexistence of cities and wetlands, people and nature.
Director
The Hong Kong Bird Watching Society, Hong Kong
Waterbird population is an important indicators of a healthy wetland ecosystem and waterbird monitoring is a common practice in wetland conservation to collect data on their population size. In Deep Bay, many are migratory which breed in Siberia in summer, and migrate southward after breeding season along a migration route known as East Asian-Australasian flyway (EAAF). As one of the most important wintering sites for migratory waterbirds, Deep Bay area with long-term waterbird monitoring is shown to hold significant EAAF populations for 13 waterbird species. Along EAAF, studies have shown that wintering populations of many species have declined in Australia and Japan; however, long term data of waterbird population along China coast are limited.
We analyzed population data collected from monthly bird surveys to quantify population trends of wintering waterbirds from 1998 to 2017 in Deep Bay area. Of the 42 species studied, 12 declined, while nine increased significantly. Phylogenetic comparative analysis revealed that population trends were negatively correlated to reliance on the Yellow Sea and body size. Further, waterbird species breeding in Southern Siberia declined more than those breeding in East Asia. This study shows that data collected from wintering sites provide insights on the patterns of declining waterbirds along EAAF and inform conservation actions accordingly.
Building on the study result, we conduct further research in Deep Bay by putting GPS loggers on Eurasian Wigeon and Black-faced Spoonbill, to track its movement and habitat use. Preliminary data show individuals had a home range covering a considerable extent of wetlands in Deep Bay area, and was using a variety of wetlands including fishponds, abandoned ponds, river channels, mudflats and geiwai, and also moved away from the Deep Bay, highlighting the knowledge gap of such diverse habitat use by the species, and the ecological function of different types of wetlands towards waterbirds.
Professor
Beibu Gulf University, China
Qinzhou Bay is not only known as the hometown of high-quality oysters-big oysters, but also the largest oyster breeding base in China. Large-scale and scattered oyster breeding rafts and oyster biomass assessment have become urgent problems in fishery management. Remote sensing images can present large-scale, high-definition oyster farming conditions. Artificial intelligence machine learning, especially target detection algorithms, have the advantages of high recognition accuracy. Therefore, this study uses the remote sensing image data of aquaculture sea area to develop a Raft-YOLO model for machine learning target detection to solve the problem of small target aquaculture raft recognition in complex backgrounds, realize accurate identification of aquaculture rafts and quickly count the biomass of oysters cultured. The experimental results show that: (1) A detection frame generation method based on the Raft-YOLO model with extended rotation angle elements is proposed, which makes it easier for the detection frame to match irregular targets under complex backgrounds. (2) The target IoU is calculated based on the intersection and union method of pixel units, which makes the loss value sensitive to the size, position and rotation angle of the label box, and is more conducive to the non-maximum suppression of NMS to control the selection of the detection box. (3) The AVG Recall of the Raft-YOLO model is 0.73, which is 0.12 higher than the YOLOv5 average recall rate of 0.61. It can be seen that the Raft-YOLO model has a better effect on the identification of oyster farming rafts. (4) Combined with the on-site oyster biomass survey and model evaluation, 4,419 aquaculture rafts and 222,100 tons of oyster resources were estimated. Therefore, the Raft-YOLO model can serve applications such as marine fishery management and typhoon disaster loss assessment.
Deputy Director
Zhanjiang Mangrove National Nature Reserve Administration
Coming soon.
Associate Professor
Shenzhen University, China
Coming soon.
Professor and Director, Simon F S Li Marine Science Laboratory, School of Life Sciences
Director, Institute of Environment, Energy and Sustainability
The Chinese University of Hong Kong
Adjunct Professor
Griffith University, Australia
Acting Head and Chair Professor of Environmental Toxicology and Chemistry, Department of Chemistry
Associate Dean (Research & Postgraduate Education) of College of Science
Director of State Key Laboratory of Marine Pollution
City University of Hong Kong
