The global problem of coral bleaching is in urgent need of attention
Recently, the U.S. National Oceanic and Atmospheric Administration and the International Coral Reef Initiative issued a joint statement saying that in the past year, more than 54% of the world's coral reefs have experienced bleaching, involving large coral reefs in the Atlantic, Pacific and Indian Oceans, affecting at least 53 countries and regions.
Coral reef bleaching is an ecological phenomenon in which colorful coral reefs turn white due to the loss of symbiotic zooxanthellae in the corals or the loss of pigment from symbiotic zooxanthellae. Global warming is one of the main causes of coral bleaching. The United Nations Environment Programme (UNEP) has warned that the average global temperature could rise by nearly 3 degrees Celsius this century above pre-industrial levels if carbon emissions are not significantly reduced. Scientists predict that even if global warming is limited to 2 degrees Celsius, about 99% of the planet's corals will be at risk of dying. If ocean temperatures do not return to normal, corals will die in large numbers, threatening coral-dependent species and food chains.
There is an increase in range and intensity
"For more than 20 years, the global problem of coral bleaching has been characterized by high frequency and wide scope." Zhao Meixia, a researcher at the Key Laboratory of Marginal Sea and Ocean Geology of the South China Sea Institute of Oceanology, Chinese Academy of Sciences, said in an interview with this reporter that in 2023, large-scale bleaching of coral reefs in the world will occur for the fourth time. This phenomenon has occurred three times before: in 1998, about 16% of the world's corals experienced bleaching due to rising ocean temperatures; In 2010, the proportion of coral reef areas affected by bleaching rose to 35 percent; Coral bleaching from 2014 to 2017 was the most widespread, affecting 56% of the world's coral reefs. Over the years, coral bleaching has increased in both scope and intensity globally.
Wang Aimin, a professor at Hainan University and chief scientist of the Hainan International Blue Carbon Research Center, said in an interview with this reporter that coral reef bleaching is distributed all over the world, but it is mainly concentrated in the following areas: in the tropical Pacific Ocean, including Guam, Hawaii, the Great Barrier Reef, etc.; In the Caribbean, including the Bahamas, Jamaica, Dominican Republic, etc.; in the Indian Ocean, including Maldives, Seychelles, Mauritius, etc.; in the Red Sea region, including Saudi Arabia and Egypt, among others; In the Gulf of Mexico, including some areas of Florida, etc. This phenomenon is also seen in parts of China, such as the Paracel Islands, the southern part of Hainan Island, the Leizhou Peninsula and the Weizhou Island in Guangxi.
In response to coral bleaching, relevant institutions around the world and some countries have taken corresponding protection measures.
According to Zhao Meixia, these measures mainly include the following types: first, global initiatives, such as the United Nations Decade of Ocean Science for Sustainable Development (Ocean Decade 2021-2030), the International Coral Reef Initiative in 2023, the Global Coral Reef Fund and the Coral Reef Breakthrough Initiative launched by high-level climate advocates; For example, the government of New Caledonia, a French overseas territory, issued a decree to establish new marine protected areas in the Coral Sea Natural Park from January 1, 2024, when 10% of the area of New Caledonia's exclusive economic zone will be designated as marine protected areas; The third is to implement ecological restoration plans, such as the Marine Ecological Protection and Restoration Project of the Ministry of Finance of the People's Republic of China and the Australian Riverbank Restoration Program. Fourth, global coral reef scientific researchers carry out academic seminars and scientific and technological cooperation, such as the International Coral Reef Research Academic Forum and the International Coral Reef Ecological Restoration Technology Symposium.
Talking about the current status of global coral reef conservation, Wang Aimin said, first, international organizations including the United Nations Environment Programme, the International Union for Conservation of Nature, the International Coral Reef Initiative, the World Wide Fund for Nature and other international organizations have played an important role in protecting and restoring coral reefs, promoting global cooperation, resource sharing and knowledge exchange; Second, many countries and regions have set up coral reef protected areas to protect coral reef ecosystems by restricting fishing, prohibiting destructive activities and strengthening management measures, such as the Great Barrier Reef Reserve in Australia and the Sanya National Coral Reef Nature Reserve in Hainan, China. Third, scientific research institutions and non-profit organizations in many countries have carried out a lot of scientific research and monitoring work to provide scientific basis and decision-making support for the control of coral reef bleaching. Fourth, many countries and regions have carried out coral conservation and restoration projects, including the establishment of coral nurseries, artificial coral breeding, artificial coral propagation and other methods to promote the growth and protection of corals; Fifth, the international community has taken a series of measures to slow down climate warming, including promoting the development of renewable energy, reducing the use of fossil fuels, and improving energy efficiency.
Global warming is the main cause
What are the factors that induce global coral bleaching?
"The symbiosis of corals and zooxanthellae is the most basic ecological feature of coral reefs." Zhao Meixia said that environmental stresses can lead to coral bleaching, such as increased temperatures, ultraviolet radiation, low temperatures, acidification, pollution and coral diseases. Among them, the abnormal increase in sea surface temperature caused by global warming is the common cause of these global coral bleaching events.
Global coral bleaching is usually caused by a combination of factors such as rising ocean temperatures, increased environmental pressure, water pollution, overfishing, and ocean acidification, Wang said. Bleaching causes the commensal algae in the coral's body to leave or die, resulting in the coral's inability to obtain adequate nutrients, stunted growth, and even death.
"Coral reefs around the world are also disturbed and damaged by human activities, such as overfishing and land-based pollutants discharged into the sea." Zhao Meixia said.
"The increase in ocean temperature caused by global warming is an important reason for the increase in coral bleaching phenomenon." Coral reefs are highly sensitive to temperature changes, and there is a positive feedback loop between climate warming and coral bleaching, Wang said. When the sea temperature exceeds a certain threshold, the coral loses its symbiotic algae and bleaching. Bleaching, in turn, leads to the death of corals and the degradation of coral reefs, further releasing carbon and greenhouse gases, and exacerbating climate warming.
Derek Manzelo, coordinator of the National Oceanic and Atmospheric Administration's Coral Reef Watch Program, said the proportion of coral areas experiencing high ocean temperatures is increasing about 1 percent each week, and it is not long before bleaching surpasses the previous peak of 56.1 percent.
"Coral bleaching reflects many problems in global marine environmental governance." Wang Aimin said that these problems mainly include: first, the lack of effective response to climate change, the lack of concerted global action and emission reduction commitments; Second, the problem of pollution and waste discharge is serious; Third, destructive activities such as overfishing, improper tourism development and seabed mining have caused varying degrees of damage to coral reef ecosystems. Fourth, the lack of effective conservation measures and management mechanisms limits the protection and restoration of coral reefs; Fifth, there is a lack of comprehensive and coordinated management methods, and there is a lack of cross-departmental and cross-border integrated management.
"There are many challenges to global coral bleaching management," he said. Zhao Meixia said that on the one hand, there are many reasons for coral bleaching, and the vulnerability of coral reefs increases the difficulty of treatment. On the other hand, the internal mechanism of coral reef bleaching is not particularly clear, and scientific research and conservation practices need to be strengthened.
Cooperative and integrated management should be strengthened
On the surface of the sea, artificial reefs have sunk to the bottom of the sea one after another; Beneath the surface of the sea, patches of corals and fish live in harmony. In the marine ranch in the sea area of Wuzhizhou Island in Sanya, Hainan, such a picture always makes Wang Aimin happy. As the first national marine ranching demonstration area in Hainan, Wang Aimin has devoted a lot of effort to the management and protection of coral reefs here.
Wang Aimin said that since the first batch of artificial reefs was put into operation in April 2011, the coverage rate of reef-building corals around the island has increased from less than 15 percent to 28.78 percent, and the coverage rate of soft corals has also increased to 9.6 percent, Wang Aimin said. The area of artificially restored coral reefs is more than 1 hectare, and more than 10 species of corals have been transplanted, with a total of more than 10,000 corals, the one-year coral survival rate is more than 90%, and the area of single species of coral has increased to nearly 10 times. At present, the marine ranch of Wuzhizhou Island has formed a complete marine biosphere such as coral reefs, fish, shrimp and shellfish, and remarkable results have been achieved in marine ecological restoration and fishery resource conservation.
Zhao Meixia said that in recent years, through continuous exploration, China has formulated a number of coral reef-related coastal ecosystem investigation and assessment technologies, early warning and monitoring technologies, and ecosystem restoration technology industry and national standards, and carried out relevant protection and restoration practices in many coral reef areas. China's plan for coral reef conservation can provide an important reference for global coral reef conservation.
"Coral reefs must be managed separately and adapted to local conditions." Researchers at the Stockholm Resilience Center in Sweden investigated the synergies between seven ecosystem services provided by coral reefs, namely coastal protection, aesthetic value, productivity, nitrogen cycle, phosphorus cycle, inorganic carbon cycle and nutritional value, and divided them into three categories based on the abundance of fish species and biomass productivity of coral reefs, namely producing trophic reefs, medium-service reefs and rich-serving reefs, according to Zhao. For these three different types of coral reefs, coral reef conservation requires greater and deeper global cooperation, and there is an urgent need to strengthen basic capacity building such as satellites and global platforms, and establish a network of marine protected areas.
"To tackle coral bleaching, governments, international agencies, research institutions, civil society organizations and the public need to work together to form a cross-sector and cross-border cooperation mechanism to ensure the long-term protection and sustainable development of coral reefs." Wang Aimin said that in order to better protect coral reefs, the world should take the following more effective measures: first, strengthen climate change response, increase emission reduction, and mitigate the impact of climate warming on coral reefs; The second is to actively protect marine carbon sink resources and carry out research on blue carbon sink enhancement technologies to help the world achieve the goal of "carbon neutrality" and provide a good marine environment for the growth of coral reefs; The third is to strengthen marine pollution control, strengthen monitoring and control of pollutant emissions, restrict the entry of plastic waste and chemical substances into the ocean, and ensure water quality health and coral reef safety; Fourth, promote sustainable fisheries management, take measures to limit overfishing, and protect marine biodiversity and the balance of coral reef ecosystems; (5) to develop and implement appropriate regulations and management measures to limit destructive human activities, including tourism development, fisheries practices, and seabed exploitation; Sixth, establish protected areas and management mechanisms, and establish more coral reef protected areas to ensure the integrity and sustainability of coral reef ecosystems; Seventh, we should carry out popular science education to enhance the public's awareness of the importance and conservation value of coral reefs, and encourage people to take environmental protection actions.
