The "mermaid" is referred to as functionally extinct in China, but the reproduction is a high probability event

Reporter | Zhang Qiannan

Edit | Zhai Ruimin

A few days ago, the paper "Functional extinction of dugongs in China" (dugongs in China) jointly published by scientists from the Chinese Academy of Sciences and the Zoological Society of London pointed out that dugongs have experienced rapid population collapse in recent decades, and the dugong population in China's waters has been functionally extinct, even if it has not yet been confirmed that the last individual has died, but the population has been reduced to unable to maintain reproduction.

Dugong dugon has a spindle-shaped body, about 3 meters long and weighs 300-500 kilograms, and is often seen as the prototype of the legend of the "mermaid". It is one of the oldest marine animals in the world, the only herbivorous mammal in the strict sense of the word, and the only extant species in the dugong family, which is listed by the IUCN as a globally vulnerable species, and currently population resources are mainly concentrated in Australia. In China, dugongs have been listed as a national key protected animal since 1988.

"Historically, dugongs have been widely found on the southeast coast of the mainland, especially in Taiwan, Hainan, Guangxi and Guangdong." Zhou Jinfeng, Vice Chairman and Secretary-General of the China Biodiversity Conservation and Green Development Foundation and expert of the Conservation, Conservation and Restoration Working Group of the International Organization for Standardization's Biodiversity Technical Committee (ISO/TC331), introduced interface news.

In the summer of 2019, the researchers conducted a large-scale interview survey of fishermen in 66 villages in 22 cities in four Chinese provinces (Hainan, Guangxi, Guangdong, Fujian) and reviewed all available historical data involving the past distribution of dugongs in Chinese waters. Of the 788 respondents, only 5 percent reported seeing dugongs in the past, with the last time they saw dugongs averaging 23 years ago.

Functional extinction refers to the reduction of the population of a certain organism or species under natural conditions to a state where it cannot maintain reproduction. The paper notes that comprehensive assessments show that even in Chinese waters there are still some dugong individuals, and under current conditions, the dramatic population decline experienced by the species in recent decades is highly unlikely to be stopped or reversed, and the continued deterioration of coastal ecosystems means that dugongs have little hope of surviving even in the short term, if they have not disappeared.

Zhou Jinfeng said that dugongs are marine herbivorous mammals, and with the intensification of marine pollution and the overexploitation of the ocean, the offshore seagrass beds have rapidly degraded and disappeared, which is the direct cause of the functional extinction of dugongs.

He introduced that the seagrass bed has high requirements for growth conditions and is easily affected by the external environment, such as the turbidity of the seawater will affect the photosynthesis of the seagrass, "just as the lively street does not grow grass, under the influence of busy shipping, the seagrass cannot grow, and the dugong loses the ecological environment on which it depends for survival." In addition, overfishing, noise, and intensive shipping all pose a threat to the survival of dugongs. ”

Wang Pilie, a researcher at the Liaoning Academy of Marine and Fishery Sciences, pointed out in an article published in 2007 entitled "Survey on the Current Situation of Dugong Resources in Hainan Province" that the biggest threat to dugong resources in the Beibu Gulf (a semi-enclosed bay in the northwestern part of the South China Sea) came from the large-scale hunting of dugongs in the late 1950s and early 1960s. According to the Guangxi Fisheries Bureau, 14 were killed in the Hepu area of Guangxi in 1958, 36 in 1959, 47 in 1960, 51 in 1961, 58 in 1962, and 216 in five years. About 30 were hunted and killed along the western coast of Hainan Island during this period, causing devastating damage to dugong resources. What is particularly serious is that from 1975 to 1976, 28 animals were killed in the Hepu waters, which made the Ruliang resources tend to extinction and it was difficult to recover.

As the protection of dugongs entered the public eye, in April 1986, the People's Government of Guangxi Zhuang Autonomous Region approved the establishment of the Autonomous Region-level Hepu Dugong Nature Reserve, and in October 1992, the State Council approved the establishment of the National Hepu Dugong Nature Reserve. Located in Hepu County, Beihai City, Guangxi Autonomous Region, the nature reserve stretches from Yingluo Port in Shankou Town in the east to the sea area of Sha tin Town in the west, with a total coastline of 43 kilometers, making it the only Dugong Nature Reserve in China.

According to the paper, historical data analysis shows that there are no public or undisclosed dugong records in China after 2008. Interface News noted that in the study of biodiversity in Guangxi Hepu Dugong National Nature Reserve, there was no trace of dugong activity for many years, and the last time it was recorded was on June 8, 2002, according to the data of Sha Tin Fishery Administration Station, 4 dugongs were witnessed in Sha tin Dingzhou Sha.

Zhou Jinfeng introduced that dugong is the flagship species of the ecosystem, and its existence or absence is an important indicator of the ecological quality of the coastal sea, "the dugong is an ally of offshore blue carbon (mainly refers to the carbon dioxide captured by marine and coastal ecosystems from the atmosphere, including various forms of carbon stored in seawater and sediments). The seagrass bed fixes carbon dioxide through photosynthesis, and the dugong feeds on seagrass and is also the seeder of seagrass, which has a positive effect on ocean carbon sequestration. The functional extinction of dugongs can have a huge impact on the entire ecosystem, leading to further deterioration of the offshore ecology.

"Although the paper points out that the remnant population of dugongs may survive in the northern part of the South China Sea, due to the loss of dugong food sources, activity sites, habitats, and perennial observation, it can be said that the current probability of dugong existence is small," Zhou Jinfeng believes.

Following the extinction of the white-tipped dolphin, the functional extinction of dugongs in China has once again sounded the alarm for the protection of endangered animals. Zhou Jinfeng pointed out that the possibility of saving the dugong species exists, and at present, it seems that it is necessary to introduce the population from the outside, and the top priority is to rebuild the dugong habitat in the offshore sea, including planting seagrass beds, setting up nature reserves, and rebuilding marine connectivity.

In view of the survival situation of dugongs, the China Green Development Council has previously set up a dugong research group to promote the reintroduction of dugongs, a precious marine species, and the restoration of the entire ecosystem on which the species depends. Zhou Jinfeng said that if the natural introduction can not be realized, you can also use semi-manual intervention to introduce dugong, there are already some experts in the world willing to participate in the dugong research group, work together in this direction, "Overall, dugong reproduction is a high probability event." ”