Wetland, Its Functions and Values;
especially on Tidalflat
Contents
Introduction
1 What Are Wetland and Tidal Flats?
1) General Wetland
2) Tidal Flats
2 Making Process of Tidal Flats
3 The Style of Tidal Flats
1) Prairie Tidal Flats
2) Sand Tidal Flats
4 Living Things in Tidal Flats
5 Functions of Tidal Flats
1)General Functions
2) Water Quality Improvement Functions
3) Economic Value of Kang-Hwa Island
6 Legal Consideration
7 Conclusion
Introduction
Korea has reclaimed lots of coastal wetland as a national policy because of her natural conditions such as small scale of land[1] and comparative high population density[2]. Moreover, Korea is a mountainous country, with less than 30% of the land area flat enough for agriculture and urban or industrial development; therefore, the shallow wetlands became obvious targets for creating new land for rice farms, aquaculture, industrial complexes and housing. By joining strings of offshore islands or closing narrow channels, the mudflats can easily be 'put to use'. In earlier history, some of the smaller inlets had already been filled, but since 1970, a coordinated program of tideland reclamation began aiming to ultimately increase Korea's land area by about 500,000 hectares, or roughly 5%.[3]
A new airport construction near the west coastal line is proceeding on the reclaimed site now. The size of new international airport is so huge that five times bigger than the Chicago O'Hare airport. That means same as the size of wetland disappeared on the earth. Other two major land fill projects[4]also in the west coastal line[5], that has not only consumed so much government budget but also produced too many side effects, are also big environmental issues in these days. The fundamental reasons of these environmental situations are from the lackness of understanding on coastal wetland or tidal flat as a so valuable natural resource. This is main reason why I choose this topic. If the economic value of the tidal flat in undeveloped conditions is higher than that of the farmland or industrial zone changed from the wetland, the projects can not be reasonable in economic and ecological criteria. In this paper, I show the functions and economic values of tidalflat to make an accurate estimate of the monetary costs associated with the loss of a free service performed by a wetland ecosystem. I believe this paper can be a useful document for proving the economic value of the wetland in the public hearing of environmental impact assessment of new reclamation projects. Moreover, this research will be helpful to stop the project in the court.
1 Definition: What Are Wetlands and Tidal flat?
1) General Wetlands
Simply and literally speaking, wetlands are lands wet by water. More technically and scientifically speaking, wetlands are lands inundated by surface water or ground water[6]. According to the EPA, wetlands are lands where saturation with water is the dominant factor determining the nature of soil development and the types of plant and animal communities living in the soil and on its surface.
For regulatory purposes under the Clean Water Act, the term wetlands means "those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar areas." [7]
Generally, when we can divide the wetland as inland wetland and coastal wetland according to the water covered the wetland, mudflat or tidal flat are included in the coastal wetland.[8]
2) Tidal flats
Tidal flats or mud flat can be defined as a broad and flat land consisting of mud or sand around river or coast that affected by tide. That is composed of tiny compounds of silt or clay delivered by tidal water on the coastal areas.[9]
Tidal flats formed by the stream in a calm coast for a long time. To form wetlands, wave strength must be weak that makes coast erode and pile process of soil must be happened. Also wide and flat land needs long time for sand and prairie to accumulate.[10]
Everywhere the river meet the sea, tidal-flats surely are formed regardless of the size. So river must be the important factor to make wetlands. Flowing rivers supply the organism and saline, which are the foods of seacreatures, from the lands to tidelands as well as move the soil. [11]
2. The Making Process of the Tidal Flats
First of all, sand and prairie are essential factors to make tidal flat. After raining, the heavy particle like sand are accumulated around the sea-mouth and the light particle like prairie are moved into the calm gulf, remote sea shore. These tidal flats become the habitat for the sea livings. With these processes, finally we can see the thesaurus of the sea resource "Tidal Flat".[12]
3. The Style of Tidal Flats[13]
Tidal flats has three types according to the wind strength for accumulation; Sand tidal flat, Prairie Tidal flat, Sand & Prairie Tidal Flat. Also there are some exceptions which don't belong to any of these three types. Among these types, let's be interested in two common types; prairies tidal flats, and sand tidal flats.
1) Prairie Tidal Flats
Prairie Tidal flats means that the rate of the sand is just around 10% but that of the prairie reaches to over 90%. At first, let's take some examples about prairie tidal flat.
The vast prairie tidal flat around the Kang-Hwa islands in Korea has 0.031mm long particles and has depth with lots of water. With these reasons it's very hard to investigate the tidal flats.
Compared with the Sand tidal flat, in prairie Tidal flats the freaks are so slight that it is hard for the sea water with the oxygen and the food to pass into the prairie. Therefore, the creatures in prairie tidal flat make the hole and pipe to influent seawater.
In addition, in prairie Tidal flats we can see lobworm more than Crustacean and shells because the lobworm lives with the accumulation materials in tidal flat.
2) Sand Tidal Flats
Sand tidal flat is a good place to catch the shells and to enjoy because of the bottom formed by sand. Usually sand tidal flat is located in the middle site of the coast. The tidal flat means that there are unique sea livings only in that tidal flat. We can see short-necked clam, spiral shellfish in the West Coast where there are some tidal flats around. And we can see the clam in East Coast.
4. Living Things in Tidal Flats [14]
Wetlands are slack and flat due to the sand and prairie to the ground. Because it's not easy to hide in wetlands, there are not various creatures in there. The creatures in wetlands got the tip for a living.
It's to live into the sand or prairie. Actually most of the creatures in wetlands dig the sand and live in to the hole getting the food in there. The creatures in wetlands have to face flow, flood and flowing in from the lands. In summer, they have to overcome the high temperature and in winter they face the heavy cold weather. Due to these reasons, the creatures live in wetlands forming the groups. Therefore, just a few kinds of creatures exist in wetlands. And these kinds which got the tip to survive in wetlands can thrive.
Let's take some example living in Tidalflat below.
Nereid
It has a long symmetry body and has knuckle and out of body. The head is composed of front knuckle and lip knuckle. In front lip knuckle, there are ocellus, palp.
Monster earthworm
They are found in mid coast in west-sea in Korea. The body is symmetry and has the long cylinder shape. Also the knuckles are in and out of the body. Usually Monster earthworm which are living in sand tidal flat gets into the accumulation and push out the sheer membrane, chitin to make Pipe. So, sand and the fragment of the shell can be attached to the pipe.
Mollusca
It has symmetry body and there are 4 parts; head, foot, body, cultch. Unlike the lobworm, it has no knuckle.
Murex
Shell is very hard and has the fist shape generally. They live in sand, prairie bottom and under the rock located along the Korean west-south shore to depth 20m.
Shellfish
They have the 6cm long and thin rectangle shape. Shell is very weak to break and is seen in sand tidal flat.
Crustacean
It has three parts; head, chest, and abdomen. But the head and the chest are connected together.
Fiddler crab
It can be seen upper site in wetlands. One of claws of male is very big and reddish.
Tiger crab
Only seen in the Yellow Sea and need to be preserved. Back and leg are weak yellow, a pair of round pattern and horizontal pattern in leg are reddish
5. Functions of Tidal flats
General wetland functions are in table 1. In here, I focused on only functions of tidalflat even though most of functions of wetland also are applied to the tidalflat.
Table 1 Wetland Function [15] ------
*Flood conveyance- Riverine wetlands and adjacent floodplain lands often form natural floodways that convey floodwaters from upstream to downstream areas.
*Protection from storm waves and erosion-Coastal wetlands and inland wetland adjoining larger lakes and rivers reduce the impact of storm tides and wave before they reach upland areas.
Flood storage- Inland wetlands may store water during floods and slowly release it to downstream areas, lowering flood peaks.
Sediment control- Wetland reduces flood flows and the velocity of floodwaters, reducing erosion and causing floodwaters to release sediment.
*Habitat for fish and shellfish-Wetlands are important spawning and nursery areas and provide source of nutrients for commercial and recreational fin and shellfish industries, particular in coastal areas.
*Habitat for waterfowl and other wildlife-Both coastal and inland wetland provide essential breeding, nesting, feeding, and refuge habitats for many forms of waterfowl, other birds, mammals, and reptile.
*Habitat for rare and endangered species- Almost 35 percent of all rare and endangered animal species either are located in wetland areas or are dependent on them, although wetlands constitute only about 5 percent of the nation’s lands.
*Recreation- Wetlands serve as recreation sites for fishing, hunting, and observing wildlife.
*Source of water supply- Wetlands re becoming increasingly important as sources of ground and surface water with the growth of urban centers and dwindling ground and surface water supplies.
*Food production- Because of their high natural productivity, both tidal and inland wetlands have unrealized food production potential for harvesting of marsh vegetation and aquaculture.
Timber production- Under proper management, forested wetlands are an important source of timber, despite the physical problems of timber removal.
*Preservation of historic, archaeological value- Some wetlands are of archaeological interest. Indian settlements were located in coastal and inland wetlands, which served as source of fish and shellfish.
*Education and research- Tidal, coastal, and inland wetlands provide educational opportunities for nature observation and scientific study.
*Source of open space and contribution to aesthetic values- Both tidal and inland wetlands are areas of great diversity and beauty, and provide open space for recreational and visual enjoyment.
*Water quality improvement- Wetlands contribute to improving water quality by removing excess nutrients and many chemical contaminants. They are sometimes used in tertiary treatment of wastewater.
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1) The General Functions of Tidal flats.
First of all,the tidalflat, as the neutral zone to connect the lands and the seas, offers the habitat and spawning ground to the various kinds of fisheries and produces the 60% of the wholeproductivity. The vast majority of fishing and shellfishing industries harvest wetland-dependent species. This catch is valued at $15 billion a year in the States. Commercial fishermen harvested nearly ten billion pounds of fish in 1996.[16]
Detritus—enriched organic material formed by the decay of plant and animal material in water—is food for insects, shellfish and forage fish. In turn, fish, mammals, reptiles and amphibians feed off of the insects and forage fish. The growth of wetland plants and algae is also nourished by nutrients the provided in the detritus. Wetland plants provide food and shelter for fish and animals.
Secondly, tidalflat can be the stopover and habitat for migratory birds.
Third, tidalflat has the enough values to study with biological view. The 30% of the extinct creatures live in tidalflat. We can develop the benefits from the tidalflat as well as the living preservation. Also we can use these living in tidalflat as food resource and medical resource.
Forth, tidalflat has the values as the tourist place with its unique sightseeing and its recreation.[17] In the world the mud massage is so popular that it has enough specialty as tourism industry.
Finally, tidalflat has the control function of natural disaster and the temperature, because it can save the largeamount of water. Especiallythe wetlands around the urban rivers can minimize the damage caused by water around building and roads. Some of the American governments think this function very important that they remake the wetlands to surf caused by typhoon and hurricane.[18]
2) Water Quality Improvement Function
The value of tidalflat for improving water quality is often overlooked. However, tidalflat can remove and transform organic and inorganic materials-including human waste, toxic compounds, and metals-from inflowing waters. [19]
As water floods into wetlands from rivers and streams, its velocity decreases, causing an increase in sedimentation. Thus, chemicals sorbed to sediments are removed from the water and deposited in the tidalflat.
A variety of anaerobic and aerobic processes also function to precipitate or volatilize certain chemicals from the water column.
The accumulation of organic peat that is characteristic of many wetlands can ultimately lead to a permanent sink of many chemicals. The high rate of productivity of many wetlands can lead to high rates of mineral uptake by, and accumulation in, plant material with subsequent burial in sediments.
Shallow water coupled with the presence of emergent vegetation leads to significant sediment plant-water exchange.
Moreover, reducing of oxygen-demanding substances such as BOD and ammonia, suspended solids, nutrients such as nitrogen and phosphorus, and other pollutants such as metals also provide the wastewater treatment.[20]
According to the result of the study in Japan comparing the natural purificationwith sewage disposal purification, the capacity of purify the contaminants is the 8% decrease per an hour. With this capacity the 96% of the whole seawater can be purified in a half a day. To get the facility with this capacity, we need 1.22 billion-dollar and need 57 million-dollar to manage it in a year. With other facilities, the total will reachto 8.78 billion dollar. Also the sewage disposal system needs the big money to manage it. On the other hand we can have a natural purification treatment as well as get the profits from the fisheries and some free function as we see above.Therefore, by restoring and utilizing functions, we can reduce the costs of constructing, operating and maintaining drinking water treatment plants.
Moreover, there is a study 1 ha tidalflat can purify the 21.7 kg BOD a day.[21] Then, 28300 ha tidalflat of Saemangum is a natural sewerage treatment that has purification capacity 100.000 ton a day.[22]
Let me take an example that comparing economic value of natural wetland and reclaimed wetland.
3) The Economy Value ofWetlands in Kang-Hwa island[23]
A. The importance
The Korean west shore has vast wetlands that are composed of fine soil. These wetlands are very rare and valuable places all over the world.
1) Function I: Fishery production & Habitat
Wetlands are called " Biological Supermarket"with the variety of sea creatures.
2) Function II: Aesthetic & Sightseeing
Wetlands are the places for fishing, sea bath, nice view and other recreation. Also the places for educational and scientific values such as fowl research and academic studies.
Recently the wetlands massage is being newly popular as its specialty.
3) Function III: Purification
According to the experiment, it is said that 10km² wetlands can purify the contaminant exhausted from the city, which has 100,000 people in 25.3km².
4) Function IV: Flood & Hurricane controller