The high water level of Poyang Lake will affect the survival of wintering waterbirds
More than 600,000 waterbirds overwinter in Poyang Lake every year, resulting in low yields of submerged plants such as bitter weeds caused by high water levels, affecting food intake; experts call for protection of waterbird habitats
The high water level of Poyang Lake threatens not only the residents of the Lake District.
As China’s largest freshwater lake and Asia’s largest wintering migratory bird habitat, Poyang Lake attracts more than 600,000 waterbirds to spend the winter here. According to the 2012 assessment of the East Asia-Australia Migration Zone Partnership Agreement, Poyang Lake ranks first in the overall weight of more than 1,000 important wetlands in the East Asia-Australia Movement Zone.
Yesterday, a reporter from the Beijing News interviewed Jia Yifei, a postdoctoral fellow at the East Asia-Australia Migratory Bird Migration Research Center of Beijing Forestry University. Since 2009, Jia Yifei has gone to Poyang Lake Wetland for several field investigations on the relationship between water level fluctuations, water birds and wetlands. Jia Yifei said that for overwintering waterbirds, excessively high water levels will destroy the growth of submerged vegetation in the wetland of Poyang Lake, which will adversely affect the feeding of overwintering white cranes and other waterbirds.
Talk about the status quo
Dozens of waterbirds come here every winter
Beijing News: Why does Poyang Lake have such an important position in China and the world?
Jia Yifei: Poyang Lake is one of the most famous waterbird wintering areas in China, and the most important waterbird wintering area in the East Asia-Australia migratory bird flight area. It is one of the 200 priority protected global ecological areas identified by the World Wildlife Fund (WWF) One.
An international cooperation project that our agency participated in in 2012 evaluated more than 1,000 important wetlands in the East Asia-Australia migration zone, taking rare and endangered waterbird species and numbers as well as the entire community's waterbird species and numbers as indicators. The Poyang Lake area ranks first in the importance of the East Asia-Australia migration zone, which is why Poyang Lake is the most famous waterbird wintering place in the world.
Beijing News: What role does Poyang Lake play in terms of the Yangtze River ecosystem?
Jia Yifei: Poyang Lake is one of the Tongjiang Lakes on the Yangtze River, and it is a typical vomiting lake. At present, due to the breakthrough of the warning water level, the water area of Poyang Lake is equivalent to 2 Shenzhen cities, reaching 4206 square kilometers.
Poyang Lake plays a huge ecological function in the Yangtze River Basin, such as flood storage, water resources protection, and biodiversity support. It maintains the ecological security of the Poyang Lake area and the middle and lower reaches of the Yangtze River. It is very important for the ecological security of the Yangtze River Basin. One of the key areas for the protection of the Yangtze River.
Beijing News: Which birds will overwinter in Poyang Lake?
Jia Yifei: Over 600,000 waterbirds overwinter here every year. There are about 50 common waterbird species, including many rare and endangered species, such as white cranes, oriental white storks, and white-headed cranes.
Poyang Lake has about 98% of white cranes, 85% of geese, 75% of oriental white storks, 25% of white-crowned cranes and nearly 20% of cygnets in the world's population. Judging from the community structure of waterbirds in Poyang Lake, wild ducks and ducks are the dominant species. The average number of geese is maintained at about 120,000 per year, and the average number of ducks is maintained at about 80,000.
Beijing News: Why do so many birds overwinter here every year?
Jia Yifei: This is closely related to the geomorphic features of Poyang Lake following the hydrological rhythm. In terms of the shape of the lake basin, Poyang Lake is a typical dish-shaped lake. The lake shore is mostly a gentle slope, presenting a unique landscape of "a summer with abundant water and a dry winter line", forming a complex wetland ecosystem, especially suitable for relying on wetlands Surviving waterfowl.
In normal years, during the dry season, the water level of Poyang Lake gradually decreases, and the continental beach gradually emerges. Typical wetland vegetation such as Carex ushers in the growth period, thus forming a "concentric circle" of "grass beach-mud flat-shallow water marsh-open water" The diverse landscapes provide suitable habitats for different types of waterbirds. Carex moss on grass beaches provides rich food resources for geese, mudflats provide habitat for shorebirds, shallow water swamps provide feeding grounds for rare cranes and storks, swans, and spoonbills, and open water is for love Floating ducks provide habitat.
Talk about influence
High water levels can adversely affect waterfowl feeding
Beijing News: What impact will the high water level have on the waterbird community?
Jia Yifei: The high water level (water depth) will adversely affect the wintering waterbirds of all feeding groups. Taking the white crane as an example, the global population of white cranes classified as critically endangered species is usually less than 3,800. Globally, there are three populations of white cranes, all of which breed on the Siberian tundra in Russia. Due to habitat loss and hunting, the population of white cranes that overwinter in Iran and India has fallen to less than ten individuals. Therefore, almost all white crane populations in the world are overwintering in Poyang Lake.
In the years of major floods, such as the 1998 and 2000 summer floods, the results of the simultaneous survey of wintering winter cranes in the same year were only 741 and 382, which were around 2,000 in the previous two years.
According to previous studies on the population of white cranes and waterbirds, when the maximum water level in summer is below 19.5 meters and the minimum water level in winter is between 8.2 and 8.8 meters, it is beneficial to maintain the population of white cranes. In winter, the white crane feeds on the overwintering tubers (winter buds) of the submerged plant bitter grass in the shallow water area of the butterfly lake. However, the study found that when the water surface exceeds the depth of 2 meters of the underwater bitter grass plant, the winter bud productivity is seriously reduced. The current water level of the Xingzi Hydrological Station has exceeded 22.5 meters, which is much higher than the optimal water level of 19.5 meters in summer. This means that the current water level is obviously in a state of unfavorable white crane populations. The high water level will greatly inhibit the vegetative growth of bitter grass in summer, resulting in The winter bud yield is low, which makes Baihe's winter food severely inadequate. The population of white cranes in Poyang Lake exceeds 98% of the world's total. If the habitat of Poyang Lake is destroyed, the white cranes may suffer from extinction.
Beijing News: In terms of maintaining the stability of waterbird populations, what is the ideal range for the water level of Poyang Lake?
Jia Yifei: The main driving force for the change of the Poyang Lake wetland is the fluctuation of the water level. This unique periodic hydrological change process is the source of life for the Poyang Lake wetland ecosystem. For all waterbird communities, the summer water level is lower than 17.4 meters, and the winter water level is maintained between 8.2 and 8.8 meters, which is an ideal range for the water level fluctuation of Poyang Lake to maintain the stability of waterbird populations.
Talk about protection
Existing wetland area is still insufficient
Beijing News: What impact did wetland reclamation have on the Poyang Lake wetland ecosystem?
Jia Yifei: One of the most important functions of wetlands is to store floods, especially Tongjiang Lakes and floodplain wetlands. During the flood period, the wetland can absorb the flood to the maximum extent like a sponge, and then slowly release excess water after the flood, thereby reducing disasters. Because the flood carried the rich sediment and nutrients deposited in the wetland upstream, this part of the wetland became the best plant growth area. Since ancient times, the cultivated land obtained from the reclamation of wetlands has the highest grain yield. Many famous hometowns of fish and rice in my country, such as Poyang Lake District, Dongting Lake District and Sanjiang Plain, are the products of wetland reclamation. However, reclamation will reduce the actual area of the lake, that is, the "sponge" becomes smaller, and the ability to absorb floods becomes weaker, so that the entire wetland regulation and other functions are weakened.
Although the policy of returning farmland to the lake implemented after 1998 can alleviate the problems caused by the loss of wetlands to a certain extent, the area of Poyang Lake is still insufficient.
Beijing News: What measures can be taken to deal with possible adverse effects?
Jia Yifei: First of all, the river basins and lakes (including the Three Gorges Dam) in the Yangtze River Basin should be comprehensively regulated in a basin-wide manner. While ensuring the safety of the people’s lives and property, they must also meet the ecological security needs of the Yangtze River Basin. Promote the work of “returning farmland to lake” to restore natural wetlands and reduce the impact of the flood and subsequent disasters.
Secondly, long-term basic research work on Poyang Lake and even the wetlands in the Yangtze River Basin should be carried out to strengthen monitoring and patrol. Without the support of scientific research, it is possible to ignore the population change trend of environmental indicator species, and even lead to the ecological disaster of species extinction. Finally, if extreme weather persists in the Yangtze River ecosystem, it is prudent to try artificial interventions including feeding to help waterbirds temporarily overcome the difficulties during the winter.
This edition was written/Reported by the Beijing News reporter Wu Linshu