What is a wetland? Wetlands are the lungs of the earth, right?

Wetland is a transitional zone between terrestrial ecosystem and aquatic ecosystem. Many wetland plants grow in a specific environment where the soil is soaked in water. Wetlands are widely distributed all over the world, and there are many wildlife resources, which are important ecosystems. The breeding and migration of many rare waterfowl are inseparable from wetlands, so wetlands are called "birds' paradise". Wetland has a strong ecological purification function, so it has the reputation of "kidney of the earth". Under the dual pressure of population explosion and economic development, a large number of wetlands were transformed into farmland in the middle and late 20th century. Coupled with excessive resource development and pollution, the wetland area has been greatly reduced and wetland species have been seriously damaged.

Wetland is a multifunctional and biodiversity-rich ecosystem on the earth and one of the most important living environments for human beings.

There are many types of wetlands, which are usually divided into natural and artificial categories. Natural wetlands include swamps, peatlands, lakes, rivers, beaches and salt marshes, while constructed wetlands mainly include paddy fields, reservoirs and ponds. According to statistics, there are 8.558 million square kilometers of natural wetlands in the world, accounting for 6.4% of the land area.

Diversity of the richest organisms in wetlands

There are more than 2760 species of wetland plants recorded in China alone, including more than 380 species of wetland higher plants 156 families and 437 genera/kloc-0. According to the growing environment, wetland plants can be divided into three categories: aquatic, swamp and hygrophytic. From the perspective of plant life forms, there are emergent, floating, submerged and floating types. In terms of plant species, there are some fine grasses, some coarse herbs, some short shrubs and some tall trees. The species of wetland animals are also extremely rich. There are about 1500 species of wetland animals recorded in China (excluding insects, invertebrates, fungi and microorganisms), including about 250 species of water and about 1040 species of fish. There are about 500 species of freshwater fish, accounting for more than 80% of the total freshwater fish in the world. Therefore, no matter from the perspective of economics or ecology, wetlands are the most valuable and productive ecosystems.

Wetlands are basically divided into five categories.

sea area

Subtidal waters: shallow waters with a water depth of less than 6 meters at low tide, including bays and straits, where there are no permanently growing plants; The aquatic vegetation layer in the subtidal zone, including various seaweeds and tropical marine meadows; cay

Intertidal waters: rocky beaches, including reefs and rocky beaches; Gravel beach; Vegetation-free intertidal sediments and saline-alkali beaches; Intertidal beach with vegetation, including mangroves on the continental shelf.

river mouth

Subtidal estuary: the estuary waters are permanent estuary waters and delta estuary system.

Intertidal estuary: intertidal mud, sand or saline-alkali beach with sparse plants; Intertidal marshes include saline-alkali meadows, tidal semi-saline marshes and freshwater marshes; Intertidal forest wetlands include mangroves, Nepalese palm trees and tidal freshwater swamp forests.

Lagoon wetland: a brackish water to a saltwater lake with one or more narrow waterways similar to the ocean.

Salt lake (inland basin): permanent and seasonal saline or alkaline lakes, mudflats and swamps.

river

Permanent rivers: permanent rivers and streams, including waterfalls; Inland delta.

Temporary rivers: rivers and streams that flow seasonally and intermittently; Flood plain, including flood plain, flood valley and seasonal flood grassland.

lake

Permanent lakes: permanent freshwater lakes (above 8km2), including lakesides that flood seasonally or intermittently; Permanent freshwater pond (above 8km2).

Seasonal lakes: seasonal freshwater lakes (above 8km2), including floodplain lakes.

Artificial water surface

Such as reservoirs, ponds and paddy fields. Belonging to a broad sense of wetlands, it has been recognized by the Convention on Wetlands.

Classification of Wetlands in the Convention on Wetlands

I. Natural Wetland China Wetland Network ()

(i) Marine/coastal wetlands

A- Permanent shallow water: In most cases, the water level is less than 6m at low tide, including bays and straits.

B- Algae layer: It includes the growth area of submerged algae, algae and tropical algae plants.

C- coral reef: coral reef and its adjacent waters.

D- rocky coast: including offshore rocky islands and seaside cliffs.

Electronic beach, gravel beach and pebble beach: including coastal sand states, headlands and sand islands; Dunes and swamps between hills.

F- Estuary waters: estuary waters and estuary delta waters.

G- mudflats: mudflats, beaches and other coastal salt marshes in the intertidal zone.

H- salt marsh; Include coastal salt marshes and salinized grasslands.

I- intertidal forest wetland: including mangrove swamp and coastal freshwater swamp forest.

J- Salty lagoons and alkaline lagoons: Salty lagoons and alkaline lagoons with channels connected with seawater.

K- coastal freshwater lakes: including freshwater delta lagoons.

ZK(a)- coastal karst cave water system. Coastal karst caves

(2) Inland wetlands

L- permanent inland delta: inland river delta.

M- Permanent rivers: including rivers and their tributaries, streams and waterfalls.

Seasonal rivers: seasonal, intermittent and periodic rivers, streams and creeks.

O lake: a permanent freshwater lake with an area of more than 8 hectares, including the Great Oxford Lake.

P- seasonal lakes: seasonal intermittent freshwater lakes larger than 8 hectares; Include flood plain lakes.

Q- Salt Lake: A permanent saline, brackish and alkaline lake.

R- seasonal salt lakes: seasonal and intermittent salt water, brackish water, alkaline water lakes and their shoals.

SP- Inland salt marshes: permanent salt water, brackish water, alkaline marshes and bubble marshes.

SS- salt marsh: seasonal and intermittent salt marsh, brackish marsh, alkaline marsh and bubble marsh.

TP- permanent freshwater herb swamp and bubble swamp; There is no peat accumulation in herb marshes and bubble marshes with an area of less than 8 hectares, and most of the growing seasons are accompanied by floating plants.

TS- flooded land: seasonal and intermittent flooded land, wet meadow and bubble marsh with an area less than 8 hectares.

Herbaceous peat land Woodless peatlands include moss peatlands and herb peatlands.

Va- alpine wetland; Including alpine meadows and temporary waters formed by snowmelt.

Vt- tundra wetland; Including temporary waters formed by alpine tundra and snowmelt.

W- shrub wetland; Shrub swamp, freshwater swamp dominated by shrubs, without peat accumulation.

XF- Freshwater forest swamp: including freshwater forest swamp, seasonal flooding forest swamp and forest swamp without peat accumulation.

XP- forest peat land; Peat forest swamp

Y- freshwater springs and oases.

ZG- geothermal wetland. Hot springs.

ZK(b)- inland karst cave water system. Underground karst cave water system

Note: "Flooded area" is a broad term, referring to one or more wetland types, which may include R, Ss, Ts, W, Xf, Xp or other wetland types. Some examples of floodplains are the seasonal inundation of grasslands (including natural wet grasslands), shrub lands, woodlands and forests. The floodplain wetland is not considered as a special type of wetland here.

Second, the constructed wetland

1- aquatic pond. Such as fish and shrimp culture ponds.

Two ponds. Including agricultural ponds and water storage ponds, the general area is less than 8 hectares.

3- irrigate the land. Including irrigation canals and rice fields.

4- Agricultural flood plain. Seasonal floods in agricultural land, including intensive management or grazing grassland.

5- Yantian. Salt drying pond, salt mining field, etc.

6- Water storage area. The water storage area formed by reservoirs, dams and dikes is generally more than 8 hectares.

7- Mining area. Water borrow pits and mining sites.

8- Wastewater treatment plant. Sewage field, treatment pond, oxidation pond, etc.

9- canals and drains. Water conveyance system.

ZK(c)- underground water conveyance system. Artificial management of water system in karst caves.

Wetlands have many functions.

It can be used as a water source to directly utilize or supplement groundwater, and can effectively control floods and prevent soil desertification, and can also intercept sediments, toxic substances and nutrients, thus improving environmental pollution; It can store carbon in the form of organic matter, reduce the greenhouse effect, protect the coast from wind and waves, and provide clean and convenient transportation ... It is called "kidney of the earth" because of its rich and beneficial functions. Wetland is also a paradise for many plants, animals, especially waterfowl. At the same time, providing food (aquatic products, livestock products, grains), energy (hydropower, peat, firewood), raw materials (reeds, wood, medicinal plants) and tourist sites for human beings is an important foundation for human survival and sustainable development.

Material production function

Wetland has powerful material production function and abundant animal and plant resources. Qilihai swamp wetland is an important bait base and source of primary productivity in Tianjin coastal areas. According to the preliminary investigation, before 1970s, there were more than 65,438+000 species of aquatic and hygrophytic plants in Qilihai, including about 40 species with ecological value. There are about 10 species of mammals and more than 30 species of fish and crabs. Reed, as the most typical plant in Qilihai wetland, covers an area of 7 186 hectares and has high economic and ecological value. It is not only an important raw material for paper industry, but also an important means of production for agriculture, salt industry, fishery, aquaculture and textile industry. It can also play a role in preventing wind and flood, improving the environment, improving soil, purifying water quality, preventing pollution and adjusting ecological balance. In addition, Qilihai can use the water surface 10000 mu, with an annual output of 2000 tons of river crabs, which is a famous river crab producing area in Qilihai.

Regulating function of atmospheric composition

The rich plant communities in wetlands can absorb a lot of carbon dioxide gas and release oxygen. Some plants in wetlands also have the function of absorbing harmful gases in the air, which can effectively regulate the atmospheric composition. But at the same time, it must be noted that wetland habitats will also emit greenhouse gases such as methane and ammonia. Marsh has great biological production efficiency. In the process of organic matter formation, plants constantly absorb CO2 and other gases, especially some harmful gases. Oxygen in the swamp is rarely consumed in the decomposition of dead plant residues. Swamp can also absorb dust and various bacteria in the air, thus purifying the air. In addition, swamp sediments have great adsorption capacity, and sewage or industrial wastewater containing heavy metals can adsorb metal ions and harmful components through swamps.

Water regulation function

Wetlands play an important role in storing water, regulating river runoff, replenishing groundwater and maintaining regional water balance. It is a natural "sponge" for water storage and flood control, which can distribute uneven precipitation in time and space, and avoid floods and droughts through the adjustment of wetland throughput. Qilihai Wetland is an important flood storage and detention area in Tianjin coastal plain, with a safe flood storage depth of 3.5-4m.

Marsh wetland has the function of moistening climate and purifying environment, and is an important part of ecosystem. Most of them are developed in negative landform types, with long-term water accumulation, dense plant growth, intertwined roots and accumulation of residues. Submerged swamps generally have tens of centimeters of grass roots. The grass-root layer is porous and has strong water-holding capacity, which can keep 3~ 15 times of its absolute dry weight. It can not only store a large amount of water, but also continuously send water back to the atmosphere through plant transpiration and water evaporation, thus increasing air humidity, regulating precipitation and playing a good role in the natural circulation of water. According to experimental research, one hectare of swamp can evaporate 74 15 tons of water in the growing season, which shows its great role in regulating climate.

Purification function

Swamp wetland is like a natural filter, which helps to slow down the flow of water. When running water containing poisons and impurities (pesticides, domestic sewage and industrial discharge) passes through the wetland, the slow speed is beneficial to the precipitation and removal of poisons and impurities. Some wetland plants can effectively absorb toxic substances in water and purify water quality.

Swamp wetland can decompose and purify environmental objects and play the functions of "detoxification" and "detoxification", so it is called "kidney of the earth". If there is no wetland, it is like a person's kidney being cut off.

For example, nitrogen, phosphorus, potassium and some other organic substances are biologically stored through complex physical and chemical changes, or they leave the wetland permanently and participate in a wider cycle through biological transfer (such as harvesting plants and fishing).

There are a considerable number of aquatic plants in swamp wetlands, including floating, buoyant and submerged plants, which have strong detoxification ability and are the bane of poisons. According to the determination, the concentration of heavy metals in wetland plant tissues is 6.5438+10,000 times higher than that in the surrounding water. Because of this, people often use this ecological function of wetland plants to purify viruses in pollutants and effectively remove "toxins" in sewage to achieve the purpose of purifying water quality.

Such as water hyacinth, cattail, reed, etc., are widely used to treat sewage and adsorb high concentrations of heavy metals such as cadmium, copper and zinc in sewage. In Florida, USA, someone did the following experiment. Let the wastewater flow through a cypress swamp (a kind of wetland) before it is discharged into the river. After determination, it is found that about 98% of nitrogen and 97% of phosphorus have been purified and eliminated, which shows the amazing removal ability of wetlands to pollutants. In Karkuta, India, there is a sewage treatment plant in the city. All domestic sewage is discharged into the constructed wetland in the eastern suburbs, and its sewage treatment cost is quite low, which has become a world model.

Provide animal habitat function

The complex and diverse plant communities in wetlands provide a good habitat for wild animals, especially some rare or endangered wild animals, and are places for birds and amphibians to breed, inhabit, migrate and overwinter.

Although the special natural environment of swamp wetland is conducive to the growth of some plants, it is not an ideal home for mammalian population, but birds can enjoy it here. Because the swamp environment is overgrown with aquatic plants, it provides a rich food source for various birds and a good condition for nesting and avoiding enemies.

There are about 200 species of birds that inhabit and haunt wetlands all the year round, such as swans, storks, pelicans, geese, egrets, goshawks, floating gulls, gulls, terns, reed warblers and predatory birds. In addition, the wetland is a stopover for birds from Siberia and northeast China to migrate southward for the winter.

Regulate local microclimate

The moisture in the wetland becomes steam through evaporation, and then falls to the surrounding areas in the form of precipitation, thus maintaining the local humidity and rainfall, making Ninghe County one of the wetter areas in Tianjin.

Different definitions

Because there is no obvious boundary between wetland and water and land, and different disciplines have different research focuses on wetland, there have been differences on the definition of wetland.

The International Convention on Wetlands adopts a broad definition of wetland, that is, whether it is natural or man-made, permanent or temporary swamp, wetland, peatlands or waters, static or flowing, or fresh water, brackish water or salt water, including water with a water depth of less than six meters at low tide. This definition includes the narrow wetland area, which is conducive to the integration of narrow wetlands with nearby waters and land, and is convenient for protection and management.

Wetland research activities usually adopt a narrow definition. In 1979, the American Fish and Wildlife Conservation Agency redefined wetland as: "At the intersection of land and water, the water level is close to or on the surface, or there is shallow water accumulation, which has at least one or more of the following characteristics:

(1) aquatic plants are the dominant species at least periodically;

(2) The subsoil is mainly wet soil;

(3) In the annual growing season, the bottom layer is sometimes submerged by water. The definition also means that lakes and wetlands are bounded by a depth of 2 meters at low water level. According to this definition, the world wetlands can be divided into more than 20 types, which have been accepted by wetland researchers in many countries.

Hydrological conditions of wetlands are the decisive factors of wetland properties. Sources of water (such as precipitation, groundwater, tides, rivers, lakes, etc. ), water depth, flow pattern, duration and frequency of floods determine the diversity of wetlands. Water has a profound influence on the development of wetland soil. Wetland soil is usually called wet soil or hydraulic soil.

other

The largest wetland in the world is Pantanal wetland in Mato Grosso, central Brazil, with an area of 25 million hectares.

Wetland science and publications

Journal of Wetland Ecology and Water Ecological Wetland Wetland Science (China)

International treaties and organizations

International Convention on Wetlands (Ramsar Convention) World Wetlands Day (February 2nd every year).

International Wetland Organization, Association of Wetland Scientists, International Council for the Protection of Birds (ICBP).

International Waterfowl and Wetland Research Bureau.

Northeast Asia Man and Biosphere Crane Reserve Network East Asia-Australia wading bird protection network

Goose and duck migration network

scientific research institution

Australia:

Australian Wetland Center University of New South Wales Wetland Ecological Research Center

United States:

National Wetland Research Center (NWRC) Florida State University Wetland Research Center

Wetland website

China Wetland Network: