[Smart Farmers] Where have all the freshwater elves gone? Freshwater biodiversity protection is urgent

"Freshwater" means water that does not contain salt. This definition distinguishes freshwater environments from marine or saltwater ecosystems. There are many types of freshwater ecosystems, such as flowing water, such as rivers, that flow from inland to the sea; still water, either shallow or deep, such as large lakes and reservoirs; and wetlands, which are areas of land that are permanently or temporarily covered by water, usually shallow, such as swamps, peatlands, estuaries, mangroves, and rice fields. Freshwater biodiversity includes organisms that live very clearly in freshwater, as well as organisms and plants that have adapted to live in or around freshwater habitats.

The image of the rushing river is from the author

The creatures living here include: fish; amphibians, such as frogs and salamanders, which can live both in water and on land; mammals, including those that rely on wetlands for survival, such as hippos and freshwater dolphins, such as Yangtze River dolphins, porpoises, seals, otters, moose, etc.; water birds, those beautiful birds that live by the water and feed on fish or insects, such as pelicans, flamingos, cranes, ducks, geese, etc.; reptiles, such as scary crocodiles, cute turtles and insidious snakes, and some insects, including the mosquitoes we hate. Aquatic plants that accompany the creatures are not just plants that live in the water, but also some aquatic plants that are rooted in the water but have stems and leaves emerging from the water. In short, there are countless creatures in freshwater.

Beautiful water birds picture from FAO

What supports so much freshwater life? Freshwater ecosystems. Freshwater ecosystems are part of the landscape and interact with the land. For example, rain that falls on the land flows into streams and rivers and fills lakes and wetlands, carrying nutrients and plant material such as seeds and leaves.

At the same time, freshwater ecosystems also supply water to the terrestrial environment. They replenish water stored underground (groundwater), which in turn supports plants living on land, such as forests, orchards, etc. These water flows are part of the "water cycle" that connects land, "groundwater", freshwater and coastal areas.

The pictures of mountains and waters are from the author

Freshwater ecosystems are habitats with rich biodiversity. These systems provide us with many services, such as drinking water, food, water transport, and recreational opportunities. There are many rivers, lakes, and wetlands that are highly valued for their recreational and cultural benefits, some of which have high economic value, such as tourism and recreational fisheries. In some developed countries, recreational fishing is also an important recreational activity and an important source of income for many communities. In my country. In recent years, recreational fishing has become one of the five major industries in the development of fisheries and one of the main means of rural revitalization.

In addition to these ecological services, freshwater ecosystems are also the main force of carbon sinks. For example, wetlands, especially peatlands, remove and store large amounts of carbon from the atmosphere. The carbon stored in peatlands alone is more than twice that of all the forests in the world. If these wetlands are destroyed, carbon will be released into the atmosphere, increasing the speed of global climate change. According to statistics, human development has destroyed 25% of the peatlands on the earth.

Freshwater ecosystems complete the water purification and filtration process for nature, and plants, animals and bacteria in forests, soils and wetlands also filter and purify water. Wetland plants are heroic contributors, absorbing some excess nutrients such as phosphorus and nitrogen and toxic substances such as heavy metals into their own bodies, preventing these harmful and toxic substances from entering drinking water. They can be considered "nature's kidneys."

Flood regulation is also a contribution of freshwater ecosystems, with many wetlands providing a natural flood barrier. Peatlands, wet meadows and floodplains at the headwaters of streams and rivers act like sponges, absorbing excess rainwater runoff and spring snowmelt and slowly releasing it into the river, where it is absorbed even more slowly by the soil, preventing sudden and destructive flooding downstream.

Freshwater coastal wetlands, such as mangroves, salt marshes, mudflats, deltas and estuaries, can serve as physical barriers, reducing water height and flow speed, thereby limiting the destructive impacts of storm surges and tidal waves. As global climate change causes sea levels to rise and extreme weather to intensify in many parts of the world, the demand for these ecological services of freshwater systems is increasing.

Freshwater ecosystems support countless animals and plants, and are home to some of the world's most endangered species. Unfortunately, these organisms are becoming extinct at an alarming rate. According to experts from the Food and Agriculture Organization of the United Nations, about 20% of freshwater fish are considered extinct or threatened, a much higher proportion than marine fish. Of the 1,200 waterbird populations with known trends, 44% are in a state of decline, and 42% of amphibian populations are declining.

The photo of the Yangtze River dolphin, a national first-class protected species, comes from the East China Sea Fisheries Research Institute

Freshwater dolphins are one of the most concerning freshwater species. Although dolphins are generally considered marine species, some dolphins only live in freshwater rivers and lakes; some marine species have adapted to living in both marine and freshwater environments. Many freshwater dolphins are now endangered or have disappeared, such as the Yangtze River Baiji, which has been considered extinct since 2006. In addition to dolphins, in the "National Key Protected Wildlife List" jointly issued and adjusted by the State Forestry and Grassland Administration and the Ministry of Agriculture and Rural Affairs in 2021, there are 4 members of the same tribe related to the Acipenser living in the Yangtze River Basin that have entered the ranks of first-class protected species. They are the Chinese sturgeon, the Yangtze sturgeon, the white sturgeon and the sturgeon. Why is this?

Because the survival of these freshwater dolphins is threatened by habitat loss and degradation, mainly due to dam construction and river diversion that reduces water flow, industrial and agricultural pollution, overfishing, and accidental capture and injury from fishing lines and nets. Internationally, the ecological status of rivers is evaluated based on the survival status of large benthic invertebrates and fish, as well as submerged plants. Therefore, ecological diversity is closely related to the health of freshwater systems.

The picture of Chinese sturgeon comes from Zhuang Ping, director of the East China Sea Fisheries Research Institute

Research on the integrity of freshwater ecosystems is an international hot topic today. Maintaining the health and stability of freshwater ecosystems has become the goal, direction and management strategy of ecosystem protection in countries around the world. The overall protection of freshwater ecosystems, promoting the overall improvement of water ecological environment quality, and improving the self-repair capacity of ecosystems are of great significance to promoting rural revitalization.

The loss of freshwater biodiversity and the degradation of ecosystems are not necessarily irreversible. I believe that through the joint efforts of the government and the public, raising public awareness of the value of freshwater ecosystems to humans and adopting more sensible management and restoration measures, our rivers, lakes and reservoirs will become more beautiful and the ecosystems will be healthier!

Produced by: Popular Science in China to Benefit Farmers

Producer: Guangming Online Science Department

Author: Liu Yadan, Research Fellow, National Chief Scientific Communication Expert, former Assistant Secretary-General of the Chinese Society of Fisheries, and Assistant Secretary-General of the China Rural Professional and Technical Association

Review expert: Pan Xiaofu, senior engineer, Kunming Institute of Zoology, Chinese Academy of Sciences

Planning: Wu Yuetong, Jiang Nan