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The United Nations General Assembly declared the “United Nations Decade for Ocean Science for Sustainable Development, 2021–2030” in December 2017 to support the successful implementation of the Sustainable Development Goals (SDG), including SDG14 on seas and oceans. Drawing on IOC documents, the review provides background information on the Decade to help promote awareness and participation of Vietnam, a country that has actively committed to the 2030 Agenda of the United Nations. The United Nations Decade of Marine Science for Sustainable Development vision is “the science we need for the ocean we want”. Decade’s mission is to “promote the transformation of ocean science for sustainable development, connecting people and our oceans”. The Decade is geared towards seven socially desirable goals of a pollution-free, ecologically healthy, predictable, safe, productive, transparent, and understood ocean. The Decade’s perspectives and directions for action encourage the scientific community, public, and decision-makers to think beyond just doing business as usual and expect real change in the process of ocean understanding and collaborative management and partnerships to support sustainable development and maintain healthy oceans. During 2019–2020, the IOC, as the coordinating body, coordinated to prepare the implementation plan for the Decade, including the operating mechanism, the method of financial mobilization and management, and the process of evaluating the Decade’s performance results.

Climate change impacts ocean nutrient availability and will likely alter the marine food web. While climate models predict decreased average ocean productivity, the extent of these changes, especially in the marginal seas upon which large human populations depend, is not well understood. Here, we reconstructed changes in seawater phosphate concentration and nitrate source over the past 400 years, which reveals a more than 50% decline in residence time of seawater phosphate, and 8%–48% decline in subsurface nitrogen supply following the coldest period of Little Ice Age. Our data indicates a link between surface ocean nutrient supply and the East Asian Summer Monsoon strength in an economically important marginal sea. As climate models predict that the East Asian Summer monsoon will strengthen in the future, our study implies that surface ocean primary productivity may increase in the South China Sea, contrary to the predicted decrease in global average ocean productivity. Ministry of Education (MOE) Nanyang Technological University Published version The research was supported by the Singapore Ministry of Education Academic Research Fund Tier 2 (award MOE2016-T2-1-016 to N. F. G. and K. A. H.), by the Earth Observatory of Singapore and the Singapore Ministry of Education under the Research Centers of Excellence initiative, and by the Taiwan Ministry of Science and Technology (MOST 110-2636-M-002-002- to H. R.)

Ocean warming is increasing the incidence, scale, and severity of global-scale coral bleaching and mortality, culminating in the third global coral bleaching event that occurred during record marine heatwaves of 2014-2017. While local effects of these events have been widely reported, the global implications remain unknown. Analysis of 15,066 reef surveys during 2014-2017 revealed that 80% of surveyed reefs experienced significant coral bleaching and 35% experienced significant coral mortality. The global extent of significant coral bleaching and mortality was assessed by extrapolating results from reef surveys using comprehensive remote-sensing data of regional heat stress. This model predicted that 51% of the world’s coral reefs suffered significant bleaching and 15% significant mortality, surpassing damage from any prior global bleaching event. These observations demonstrate that global warming’s widespread damage to coral reefs is accelerating and underscores the threat anthropogenic climate change poses for the irreversible transformation of these essential ecosystems.

The Province of Khanh Hoa, Vietnam, is located in the western South China Sea and boasts a shoreline of 385 km and many islands. Previous studies have indicated the extreme diversity and abundance of coral reefs in its waters as compared with other coastal provinces of Vietnam. A study on the resilience of coral reefs against increased surface water temperature and anthropogenic impact is conducted at 19 reef sites in 2015. At each site, a series of parameters (e.g., coral covers, genus diversity, and coral recruitment, substratum heterogeneity, depth, water exchange level, and sediment deposit and water temperature) are measured quantitatively or semi-quantitatively. The measured data are rated based on the relationship between the parameter values and coral susceptibility; the consideration that reef health reflects the biological capability to adapt to environmental changes and the recruitment potential if bleached; and positive or negative influences of physical factors in the mitigation of thermal stress and protecting corals from bleaching. A cumulative analysis enables researchers to divide the studied reefs into four categories based on varying levels of reef health to support resilience, recovery, and vulnerability in the case of increased water temperature. Relevant management interventions for each category and other supporting activities are suggested to enhance management effectiveness and to plan the rehabilitation of coral reefs for biodiversity conservation and touristic development, taking into account the involvement of related stakeholders.

Given predicted increases in urbanization in tropical and subtropical regions, understanding the processes shaping urban coral reefs may be essential for anticipating future conservation challenges. We used a case study approach to identify unifying patterns of urban coral reefs and clarify the effects of urbanization on hard coral assemblages. Data were compiled from 11 cities throughout East and Southeast Asia, with particular focus on Singapore, Jakarta, Hong Kong, and Naha (Okinawa). Our review highlights several key characteristics of urban coral reefs, including “reef compression” (a decline in bathymetric range with increasing turbidity and decreasing water clarity over time and relative to shore), dominance by domed coral growth forms and low reef complexity, variable city-specific inshore-offshore gradients, early declines in coral cover with recent fluctuating periods of acute impacts and rapid recovery, and colonization of urban infrastructure by hard corals. We present hypotheses for urban reef community dynamics and discuss potential of ecological engineering for corals in urban areas.

The South China Sea in the Central Indo-Pacific is a large semi-enclosed marine region that supports an extraordinary diversity of coral reef organisms (including stony corals), which varies spatially across the region. While one-third of the world’s reef corals are known to face heightened extinction risk from global climate and local impacts, prospects for the coral fauna in the South China Sea region amidst these threats remain poorly understood. In this study, we analyse coral species richness, rarity, and phylogenetic diversity among 16 reef areas in the region to estimate changes in species and evolutionary diversity during projected anthropogenic extinctions. Our results show that richness, rarity, and phylogenetic diversity differ considerably among reef areas in the region, and that their outcomes following projected extinctions cannot be predicted by species diversity alone. Although relative rarity and threat levels are high in species-rich areas such as West Malaysia and the Philippines, areas with fewer species such as northern Vietnam and Paracel Islands stand to lose disproportionately large amounts of phylogenetic diversity. Our study quantifies various biodiversity components of each reef area to inform conservation planners and better direct sparse resources to areas where they are needed most. It also provides a critical biological foundation for targeting reefs that should be included in a regional network of marine protected areas in the South China Sea.

The South China Sea in the Central Indo-Pacific is a large marine region that spans an area of more than 3 million km2 bounded by the coastlines of ten Asian nation states and contains numerous small islands. Although it abuts the western border of the Coral Triangle, the designated centre of maximum marine biodiversity, the South China Sea has received much less scientific and conservation attention. In particular, a consolidated estimate of the region’s scleractinian reef coral diversity has yet to emerge. To address this issue, we assemble a comprehensive species distribution data set that comprises 16 reef areas spread across the entire South China Sea. Despite containing less than 17 % of the reef area as compared to the Coral Triangle, this region hosts 571 known species of reef corals, a richness that is comparable to the Coral Triangle’s based on a standardised nomenclatural scheme. Similarity profile analysis and non-metric multidimensional scaling demonstrate that most areas are compositionally distinct from one another and are structured according to latitude but not longitude. More broadly, this study underscores the remarkable and unexpected diversity of reef corals in the South China Sea.

The South China Sea is an area of globally significant biological diversity. The Transboundary Diagnostic Analysis prepared for this marine basin identified the issue of coastal habitat degradation and loss as a key priority issue for action. The UNEP/GEF project entitled “ Reversing Environmental Degradation Trends in the South China Sea and Gulf of Thailand ” (SCS project) focused on these concerns through implementing a series of activities under the component on habitat degradation and loss. Important outputs of this project component were national reports on coastal habitats. This paper reviews and analyses available information from these reports and recent studies to present a review of the status and trends in coastal habitats of the South China Sea. This includes a technical summary of the best available information relating to the: distribution and extent of the dominant coastal habitats of mangroves, coral reefs, and seagrass; richness of habitat building species and hotspots of biodiversity; ranking of threats and the related rates of coastal habitat degradation and loss; and the state of coastal habitat management regimes. The use of this information in developing National Action Plans for habitats and the Strategic Action Programme for the South China Sea is reviewed. It is concluded that the science-based planning fostered by the SCS project was essential in reaching multi-lateral agreement on the regional targets and priority actions for coastal habitat management in this transboundary water body.

The United Nations Environment Programme (UNEP)/Global Environment Facility (GEF) project entitled “ Reversing Environmental Degradation Trends in the South China Sea and Gulf of Thailand ” developed and operated a regional network of 23 coastal habitat demonstration sites and land-based pollution pilot activities from 2002 to 2008. This network generated examples of best practice in coastal habitat and land-based pollution management that were documented, shared regionally, and used to inform the development of National Action Plans and the Strategic Action Programme for the South China Sea. Examples of these best practices include: strengthened cross-sectoral coordination and management; involvement of stakeholders in development of fisheries refugia ; involvement of the private sector in coastal management; building capacity of local government and communities for law enforcement; changes in awareness and habits by local communities and industry participation in land-based pollution prevention; integration of traditional knowledge and practices into management planning; adoption of supplementary and alternative livelihoods as tools for improved habitat and resource management; promotion of sustainable tourism in coastal areas; rehabilitation of habitats and sustainable aquaculture practices; and bilateral cooperation for transboundary water resource management. Each of these best practices are reviewed and discussed from the perspectives of lessons learned and opportunities for their replication and scaling-up. The role of the network of demonstration sites in integrating local governments and communities within national and regional frameworks and in generating bilateral co-operation for natural resource and environmental management in the South China Sea marine basin is highlighted as a key innovation in transboundary water resource management that has potential for future application both in Southeast Asia and elsewhere.

Restoration of coastal reefs in the South China Sea started in the 1990s in response to widespread degradation of reef habitats. A wide variety of restoration techniques is practiced including coral transplantation, substrate modification, and non-coral species stock enhancement. Interesting lessons are derived from these experiences. Protection and management remains the foremost option and should continue to be strengthened. Restoration is more costly and has its limitations, but is at the same time regarded as necessary to address extensive reef loss. Much can be gained from the sharing of information and the combined experience will help to advance the science of reef restoration for the region.