Wetland

How Wetlands Develop

Kinds of Wetlands

Climate

Geography of Wetlands

Plant Life

Animal Life

Human Life

The Food Web

Spotlight on Wetlands

For More Information

Wetlands are areas covered or soaked by ground or surface water often enough and long enough to support special types of plants that have adapted for life under such conditions. Wetlands occur where the water table (the level of groundwater) is at or near the surface of the land, or where the land is covered by shallow surface water (usually no deeper than about 6 feet [1.8 meters]). They form the area between places that are always wet, such as ponds, and places that are always dry, like forests and grasslands.

Many wetlands are not constantly wet, experiencing what is called a wet/dry cycle. Some are wet for only part of the year, like those that are drenched during heavy seasonal rains. Some have no standing water but, because they are near the water table, their soil remains saturated (soaked with water). Others may dry out completely for long periods, sometimes years.

Wetlands are among the world’s most productive environments with high biodiversity (a large variety of life forms). Only rain forests and coral reefs have more biodiversity.

Wetlands are found all over the world, in every climate from the frozen landscape of Alaska to the hot zones near the equator, except Antarctica. In the continental United States, there are about 110,000,000 acres (44,500,000 hectares) of natural wetland, and some types are found in every state. Alaska contains about 175,000,000 acres (71,000,000 hectares) of wetlands.

How Wetlands Develop

Wetlands have a life cycle that begins with their formation and may involve many changes over time.

Formation

Many wetlands were formed when glaciers retreated after the last ice age, about 10,000 years ago. Some of the glaciers left depressions

in the ground, called kettles, which were perfect places for water to gather. In some places, buried ice melted to form kettle lakes that eventually turned into wetlands.

Wetlands are formed by overflowing river banks and changes in sea level (the average height of the sea) that leave behind waterlogged areas. Some wetlands are formed with help from beavers making dams that cause rivers or streams to back up and flood the surrounding area. Landslides or centuries of heavy winds may change the terrain or carve out depressions in the ground where water then collects.

Climate plays a key role in the formation of wetlands. Lots of rain and little drainage, for example, can cause the ground to become waterlogged.

Succession

Wetlands are constantly changing as their plant and animal life changes. This process is called succession. For example, one type of floating plant, such as pondweed, begins to fill up a pond or lake. The waste from these plants, such as dead stems and leaves, makes the water thick, shallow, and slower moving. As a result, plants that must be

anchored in soil, such as reeds and grasses, can grow. As waste matter continues to accumulate, the pond gradually becomes wetland. As succession continues, the wetland eventually disappears and is replaced by dry ground.

Kinds of Wetlands

The three main types of wetlands are swamps, marshes, and peat-lands. They can be identified by size, soil type, plant populations, and the type and amount of water they hold. Some wetlands located inland are fresh water, while coastal wetlands may be fresh or salt water. Many areas contain several different types of wetlands. The Great Dismal Swamp in Virginia, contains both peat bogs and freshwater swamps.

Swamp

A swamp is a wetland characterized by poorly drained soil and plant life dominated by trees. Swamp soil is usually saturated for most of the year. The water can range from 1 inch (2.5 centimeters) to more than 1 foot (30 centimeters) deep.

Because swamp ground is constantly waterlogged, trees and plants that grow must be able to tolerate having their root systems wet for long periods of time. The water is stagnant (without movement) and the dead plant matter that settles on the bottom receives little oxygen. Without oxygen, the dead matter cannot fully decay. This gives the swamp its characteristic brown water and unpleasant smell.

Swamps are usually found in low-lying areas near rivers or along coastal areas. They get water from the overflow of the river or from ocean tides. Inland swamps always contain fresh water, but coastal swamps may contain either fresh or salt water.

In the eastern United States, some swamps, called pocosins, form in upland areas. The term pocosin comes from the Algonquin phrase meaning “swamp on a hill.” Rain is usually their only source of water, meaning the soil is low in minerals and nutrients that come from ground water. Drainage is poor in pocosins and the saturated soil is acidic (high in acids). In this environment, decomposition (breaking down) of waste is slow, and decaying matter accumulates over time. Sometimes pocosins are flooded by slow-moving streams.

Freshwater swamp

Freshwater swamps develop near the edges of lakes and next to rivers that overflow their banks. Partly decayed plant matter and stagnant water soon create swamp conditions. The Everglades in Florida, the Okefenokee Swamp in Georgia, and the Great Dismal Swamp in North Carolina and Virginia, are examples.

Saltwater swamp

A saltwater swamp is formed by the ebbing (receding) and flowing of the ocean tides. (Tides are a rhythmic rising and lowering of the oceans caused by the gravitational pull of the sun and moon.) When the tide is low, flat areas of the swamp are not under water. Saltwater swamps can be found in New Guinea, Indonesia, Kenya, Zaire, along the Mekong River in Vietnam, and along the Ganges River in India.

In some low-lying coastal areas regularly flooded with sea water, mangrove swamps develop. A mangrove swamp is a coastal, saltwater wetland found in tropical and subtropical climates such as southern Florida and Puerto Rico. (Tropical and subtropical climates are found in areas close to the equator and are characterized by warm weather.) The mangrove swamp supports salt-loving shrubs and trees such as the man-grove, from which it takes its name. Few other woody plants grow there because of the high salt content.

Marsh

Marshes are the most common type of wetland. They are dominated by nonwoody plants such as grasses, reeds, rushes, and sedges. Some marshes are so thickly covered with vegetation they look like fields of grass.

Marshes are usually found in temperate climates where summers are hot and winters are cold. They often form at the mouths of rivers (the point where a river enters into a larger river or ocean), especially those having large deposits of soil and sand, called deltas. They also form in flat areas frequently covered by shallow fresh or salt water.

Freshwater marsh

Freshwater marshes are the most common of the world’s temperate wetlands. Some receive no rain, and most are found along the edges of lakes and rivers or where groundwater, streams, or springs cause flooding. The Camargue in the Rhône Delta in southern France is an example. Different types of freshwater marshes include prairie potholes, riparian areas, wet meadows, and washes.

Prairie potholes are small marshes found by the millions throughout the north central area of the United States and south central Canada. Usually no more than a few feet deep, they may cover as much as 10,000 acres (4,000 hectares). Prairie potholes are important to migratory waterfowl as places to rest, feed, and nest. In Africa, these small marshes are called dambos. In North America it is estimated that two-thirds of all waterfowl are hatched in prairie potholes.

Wet meadows are freshwater marshes that frequently become dry. They look like grasslands but the soil is saturated. They are common in temperate and tropical regions around the world, including the midwestern and southeastern United States. Their dominant plants are sedges, flowering plants that resemble grass.

Riparian wetlands are marshes found along rivers and streams. They range in width from a few feet (meters) to as much as 12 miles (20 kilometers). Smaller riparian wetlands are common in the western United States. Larger ones are located along large rivers, such as the Amazon in South America. Riparian wetlands are unique from others in that the vegetation and life forms found immediately adjacent to the river or streams differ from those of the surrounding area, usually a forest. This marked contrast produces a diversity and enhances the benefits for wild-life, both in food (grasses and sedges) and in shelter (shrubs and trees) in a relatively small place.

A wash is a dry streambed that becomes a wetland only after a rain. Washes are found in dry plains and deserts. The plant life they support usually has a short growing season and disappears during dry periods. In North Africa and Saudi Arabia washes are called wadis. In the American west they are called arroyos.

Saltwater marsh

Saltwater marshes, also called salt marshes, are found in low, flat, poorly drained coastal areas. They are often flooded by salt water or brackish water (a mixture of both fresh and salt water). Saltwater marshes are especially common in deltas, along low seacoasts, and in estuaries (arms or inlets of the sea where the salty tide washes in and meets the freshwater current of a river). They can be found in New Zealand, in the Arctic, and along the Atlantic, Pacific, Alaskan, and Gulf coasts.

Saltwater marshes are greatly affected by tides, which raise and lower the water level on a daily basis. A saltwater marsh may have tidal creeks, tidal pools, and mud flats, each of which has its own ecosystem (a network of organisms that have adapted to a particular environment).

The high salt content of the sea water in the marsh makes it hard for plants to adapt. Grasses such as marsh grass, cord grass, salt hay grass, and the grasslike needlerush thrive here.

Peatland

Peatlands are wetlands in which peat has formed. Peat is a type of soil made up of the partially decayed remains of dead plants, such as sphagnum moss and even trees. In peatlands, dead plant matter is produced and deposited at a greater rate than it decomposes. Over time, sometimes over thousands of years, a layer of this plant matter is formed that may be as deep as 40 feet (12 meters). Several conditions are necessary for peat to form. The soil must be acidic, waterlogged from frequent rains, and low in oxygen and nutrients. The bacteria responsible for decomposing plant matter cannot thrive under these conditions, resulting in accumulation of the layers of partially decayed plant matter.

Peatlands cover three percent of Earth’s land and freshwater surface area. Peatlands are located in colder, northern climates and in the tropics. They can be found in Russia (mainly Siberia), China, Scandinavia, northern Europe, England, Ireland, Canada, and the northern United States.

The types of peatlands are temperate bogs, fens, and tropical tree bogs.

Temperate bog

Ninety percent of peatlands are found in northern temperate climates where they are called bogs. Bogs have a soft, spongy, acidic soil that retains moisture, which comes primarily from rainwater. Some bogs have taken as long as 9,000 years to develop and are sources of peat that can be burned as fuel.

Temperate bogs have been described as soft, floating carpets. The carpet is made mostly of sphagnum moss, which can be red, orange, brown, or green and may grow as long as 12 inches (30 centimeters). Sphagnum moss can grow in an acidic environment. It holds fresh rain-water in which other bog plants can grow. The high concentration of sphagnum moss has led other bog plants to develop unusual adaptations for obtaining nutrients. For example, the bog myrtle forms a partnership with the bacteria in its roots to get extra nitrogen. Other plants that grow in bogs include grasses, small shrubs such as leatherleaf, flowering plants such as heather, and poison sumac. Some rare wildflowers, such as the lady slipper orchid and the Venus flytrap, are found in bogs.

Most bogs lie in depressed areas of ground. Some, called raised bogs, grow upward and are about 10 feet (3 meters) higher than the surrounding area.

Blanket bogs are shallow and spread out like a blanket. They form in areas with relatively high levels of annual rainfall. Their average depth is 8 feet (2.6 meters). Blanket bogs are found mainly on lowlands in western Ireland and in mountain areas. After a heavy rainfall, bogs located on steep slopes can wash down like a huge landslide of jelly and cover cattle, farms, and even villages.

Nature’s Diapers

Sphagnum moss, which is found in bogs, can absorb many times its weight in water. At one time, certain Native Americans dried this moss and used it as diapers for their babies.

Fen

When a peatland is less acidic and is fed by mineral-rich groundwater, it is called a fen. Plants characteristic of fens are grasses, sedges, and reeds rather than sphagnum moss, and the soil does not become as acidic as in a bog. Less peat accumulates in a fen and it becomes only about 6 feet (2 meters) thick. As plant matter accumulates in a fen over time, it may form a raised bog.

Tropical tree bog

Bogs found in tropical climates are called tree bogs. These bogs produce peat from decaying trees rather than from sphagnum moss. The trees most commonly found in these bogs are broad-leaved evergreens. Temperatures are warmer than in temperate regions, causing decay to occur more rapidly. As a result, not as much peat develops. The only source of water is rain.

Tropical tree bogs can be found in South America, Malaysia, Africa, and Indonesia.

Climate

Unlike some other biomes, wetlands do not have a characteristic climate. They exist in polar, temperate, and tropical zones, but not usually in deserts. They are very sensitive to changes in climate, such as a decrease in precipitation (rain, sleet, or snow). The amount of precipitation and changes in temperature affect the growth rate of wetland plants. Some wetlands are seasonal, which means they are dry for one or more seasons of the year.

Temperature

Temperatures vary greatly depending on the location of the wetland. Many of the world’s wetlands are in temperate zones (midway between the North and South Poles and the equator). In these zones, summers are warm and winters are cold, but temperatures are not extreme. Wetlands found in the tropic zone, which is around the equator, are always warm. Temperatures in wetlands on the Arabian Peninsula, for example, can reach 122°F (50°C). In northeastern Siberia, which has a polar climate, wetland temperatures can be as cold as –60°F (–51°C).

Rainfall

The amount of rainfall a wetland receives depends upon its location. The average rainfall for wetlands in Wales, Scotland, and western Ireland is about 59 inches (150 centimeters) per year. Wetlands in Southeast Asia, where heavy rains occur, can receive up to 200 inches (500 centimeters). In the northern areas of North America, wetlands exist where as little as 6 inches (15 centimeters) of rain fall each year.

Geography of Wetlands

The geography of wetlands involves landforms, elevation, and soil.

Landforms

Landforms found in wetlands depend upon location, soil characteristics, weather, water chemistry, dominant plants, and human interference. Their physical features are often short-lived, especially if they are near floodplains or rivers, which can cause abrupt changes. Wetlands usually form in a basin where the ground is depressed, or along rivers and the edges of lakes.

Elevation

Wetlands are found at many elevations (the height of an area in relation to sea level). Some wetlands in the Rocky Mountains in North America, for example, are at an elevation of 10,000 feet (3,048 meters).

Elevation is used to help classify some wetlands in Ireland. Bogs that are less than 656 feet (200 meters) above sea level are called Atlantic blanket bogs. Those that are more than 656 feet (200 meters) above sea level are called mountain blanket bogs.

Soil

An important characteristic of a wetland is its soil. Soil composition helps to determine the type of wetland and what plants and animals can survive in it. Almost all wetland soils are at least periodically saturated.

Wetland soils are hydric. This means they contain a lot of water but little oxygen. Only plants that that can adapt to these wet soils live in wetlands. The nutrients in the soil often depend upon the water supply. If the water source is primarily rain, the wetland soils do not receive as many minerals as those fed by groundwater. Soil in floodplains is very rich and full of nutrients, including potassium, magnesium, calcium, and phosphorus.

In some bogs associated with forests, decaying plant matter fully decomposes and is combined with sediments to form muck. This type of soil is dark and sticky. To be classified as muck, soil must contain not less than 20 percent organic (derived from living organisms) matter.

Plant Life

An important characteristic of any biome is its plant life or lack of plant life. More than 5,000 species of plants live in or near wetlands. Wet-lands have high biological productivity (the rate at which life forms grow in a certain period of time). The higher its plant productivity, the more animal life a wetland can support. The kinds of plants found in a wetland are determined by several factors, especially the type of soil and the quantity of water.

Some plants, called hydrophytes, grow only in water or extremely wet soil. Sedges are an example. Mesophytes, such as reeds, need moist but not saturated soil. When a wetland dries up,

A Useful Nuisance

People often grumble about the water hyacinth because it multiplies and spreads quickly in open water. The plants become so thick that boats have a hard time moving through them. The water hyacinth has an important use, though. It absorbs and neutralizes many pollutants that would otherwise contaminate the water. It also has a high nutrient content, which makes it a good fertilizer.

the area may fill with plants called xerophytes. These are plants adapted to life in dry habitats and can survive where other wetland plants would wilt.

A submergent plant grows beneath the water and is found in deep marshes and ponds. Even its leaves are below the surface. Submergents include milfoil, pondweed, and bladderwort, an insect-eating plant.

Found in deep marshes, floating aquatics float on the water’s surface. Some, like duckweed, have free-floating roots. Others, including water lilies, water lettuce, and water hyacinths, have leaves that float on the surface, stems that are underwater, and roots that are anchored to the bottom.

An emergent plant grows partly in and partly out of the water. The roots are usually under water, but the stems and leaves are at least partially exposed to air. They have narrow, broad leaves, and some produce flowers. Emergents include reeds, rushes, grasses, cattails, and water plantain.

Algae, fungi, and lichens

It is generally recognized that algae (AL-jee), fungi (FUHN-ji), and lichens (LY-kens) do not fit neatly into the plant category.

Algae

Most algae are one-celled organisms too small to be seen by the naked eye. They make their food by a process called photosynthesis (foh-toh-SIHN-thuh-sihs). Photosynthesis is the process by which plants use the energy from sunlight to change water and carbon dioxide from the air into the sugars and starches they need. Some wetland algae drift on the surface of the water, forming a kind of scum. Others attach themselves to weeds or stones. Some grow on the shells of turtles or inside plants or animals. Microscopic algae that can be found in saltwater marshes include diatoms and green flagellates (FLAJ-uh-lates). Desmids are a type of green algae found in bogs.

Fungi

Fungi are plantlike organisms that cannot make their own food by means of photosynthesis; instead, they grow on decaying organic matter or live as parasites (organisms that depend upon another organism for food or other needs).

Fungi grow best in a damp environment, which makes wetlands a favorable home. Common wetland fungi include mushrooms, rusts, and puffballs.

Lichens

Lichens are combinations of algae and fungi. The alga produces food for both itself and the fungi by means of photosynthesis. It is believed the fungus absorbs moisture from the air and provides shade. One of the most common wetland lichens is reindeer moss, an important food source for northern animals such as caribou.

Green plants

Most green plants have several basic requirements: light, air, water, warmth, and nutrients. In a wetland, light and water are in plentiful supply. Nutrients, primarily nitrogen, phosphorus, and potassium, are obtained from the soil. Some wetland soils are lower in these nutrients and low in oxygen. As a result, many wetland plants have special tissues with air pockets that help them survive.

Trees that grow in swamps, such as the mangrove and bald cypress, have shallow roots. Due to the lack of oxygen in the soil, the roots remain near the surface. Other trees found in mild climates include willows and alders. Palms are found in warm climates.

Wetland plants are classified as submergents, floating aquatics, or emergents, according to their relationship with water.

Common green plants

Common wetland green plants include mangrove trees, insectivorous plants, reeds, rushes, and sedges.

Trees that live in wetlands must tolerate having their roots wet for a long period of time. One of the best examples of this is the mangrove tree, which grows in tropical and subtropical saltwater swamps. Mangroves have done so well adapting to wetland conditions that there are more than 34,000,000 acres (14,000,000 hectares) of them in the world. One of the largest mangrove forests is the Sundarban Forest in Bangladesh. Mangroves can also be found in southern Florida and other tropical and subtropical areas.

The Hat Thrower

An unusual fungus called a hat thrower grows on dung (animal waste) deposited in wetlands. The fungus forms a tiny black bulb that looks like a hat. The hat explodes under pressure and pieces get thrown outward from the fungus and attach to other plants. When an animal eats those plants, the hat thrower passes through its digestive system. When the animal defecates, a new fungus grows on the pile of dung.

Attack of the Killer Plant

Insectivorous (insect-eating) plants, such as the sundew, the pitcher plant, and the Venus flytrap, need nitrogen to survive. These plants live in bog areas where the soil is acidic and nitrogen and phosphorus are not readily available. In order to obtain the proper nutrition, they trap insects, dissolve them, and absorb their nutrients, which include these essential nutrients.

The Venus flytrap, for example, has toothed “jaws” at the end of its leaves. These jaws spring shut when an insect in search of nectar touches the sensitive hairs inside. The plant eats the insect by dissolving it with digestive juices and absorbing it through its leaves. After the insect has been digested, the plant opens its jaws again and waits for the next victim.

Venus flytraps are found in the marshy coasts of North and South Carolina. These plants grow only under certain conditions and are popular houseplants. As a result, they sometimes have been overharvested.

Some non-tropical mangroves have special membranes that reduce the entry of salt into their systems. Mangroves get some of their oxygen from pores in their roots, the largest portions of which are above ground, and from small gaps in their bark.

Mangrove flowers are pollinated by the wind, insects, birds, or bats. The seedlings begin to grow while they are still attached to the parent tree. Seedlings germinate (grow) within the fruit that contains them. The root, or roots, of the maturing seedling then break through the outer wall of the fruit. When the seedling reaches a mature enough stage, it is released from the parent plant, floats on the water, and then settles in mud, where it establishes roots and begins to grow.

Two common peatland plants eat insects. The sundew eats ants by catching them in a sticky liquid on its leaves. It then releases chemicals that break down the ant’s body so the plant can absorb the nutrients. The pitcher plant gets its name from the shape of its leaf, which looks like a pitcher. If an insect crawls down the leaf it cannot crawl back up because the leaves have downward pointing hairs and are too slippery. It is then digested by chemicals in the plant.

A reed is a type of grass with tall, feathery flowers, with round, hollow stems, and long, flat, narrow straplike leaves. Rushes and sedges are grasslike, but they are not true grasses. Rushes have round, solid stems and narrow, rigid leaves. Sedges have solid, triangular stems.

Reed mace and common reeds play a key role in wetland succession. They reproduce widely through their rhizomes (underground stems). As the plants spread out, they push aside other plants and quickly choke up a pond, slowing the water’s movement and trapping dead plant matter. As this matter accumulates, the pond fills up and becomes a marsh.

Growing season

Climate and precipitation effect the length of the growing season in a wetland. Warmer temperatures and moisture usually signify the beginning of growth. In regions that are colder or receive little rainfall, the growing season is short. Growing conditions are affected by the amount of moisture in the soil, which ranges from saturated to dry. Although many wetland plants die during dry periods, their seeds remain in the soil all winter and sprout in the spring.

Reproduction

Green wetland plants reproduce by several methods. One is pollination, in which the pollen from a flowering plant’s male reproductive part, called the stamen, is carried by wind or insects to the flowering plant’s female reproductive part, called the pistil. Water lilies, for example, are closed in the morning and evening, but open during midday when the weather is warmer and insects are more active. It is usually at this time that the insects pick up the pollen and transfer it from the stamen to the pistil, allowing pollination to occur.

Some wetland plants send out rhizomes, which are stems that spread out under water or soil and form new plants. Reed mace and common reeds are examples.

Endangered species

One-third of the endangered plants in North America are dependent upon wetlands for their survival. As of January 2008, there were 1,046 endangered and 305 threatened plants in the United States protected under the U.S. Endangered Species Act.

Changes in the habitat, such as succession, pollution, and new weather patterns, endanger wetland plants. They are also endangered by people who collect them. Rare species of orchids are an example, as is the Venus flytrap, which has become a popular houseplant and has been overharvested. Peat moss is overharvested because it is popular as fuel, packaging material, and in gardens.

Animal Life

Wetlands have been called “biological supermarkets.” Besides animals that live there permanently, many nonwetland animals, such as opossums, raccoons, and skunks, visit for food and water. Wetlands provide shelter for mammals such as minks, moose, and muskrats. Wetland conditions make it necessary for the animals that live there permanently to adapt in special ways.

Microorganisms

Microorganisms cannot be seen by the human eye. Those found in wetlands include protozoa and bacteria. Protozoa are single-celled animal-like protists that feed on bacteria and other microorganisms. Other protozoa are parasites that live on aquatic plants, on damp ground, or inside animals or plants. Protozoa are not capable of

The Persistent Marsh

For more than 2,000 years popes, emperors, and government officials tried to drain the Pontine Marshes where malaria-carrying mosquitoes like to live. Located in south-central Italy, the marshes are bordered by the Tyrrhenian Sea, the Lepini Mountains, and the Alban Hills.

All attempts to completely drain the marshes failed. The area survived and about 300 square miles (777 square kilometers) of the original marsh is now a national park with native vegetation intact. With the help of water from the marsh, the area is now one of the most agriculturally productive in Italy. Crops grown in the area include sugar beets, fruits, grains, and vegetables. Livestock is also raised here.

photosynthesis. Bacteria are also single-celled; most cannot make their own food and must obtain it from the environment. Blue-green bacteria are plantlike, photosynthetic algae that can make their own food.

Some protozoa cause malaria, a disease characterized by chills, fever, and sweating. Mosquitoes carry malaria and spread the disease to humans. Malaria is found in temperate, subtropical, and tropical regions. Spread of the disease has been greatly reduced due to the use of pesticides to kill mosquitoes, but it remains a problem in parts of Africa and southeastern Asia.

Invertebrates

Invertebrates are animals without a backbone. They range from simple sponges to complex animals like insects, snails, and crabs.

Thousands of species of insects have adapted to life in wetlands. Some spend their entire lives in the water. Others live in the water while young, but leave it when they become adults. Still other insects have gills, just like fish, which enable them to obtain oxygen from the water; and some breathe air. For example, the diving beetle traps air in the hairs on its body or under its wings, which helps it to float. Water spiders create bubbles of air under the water in which they feed and lay eggs. The water spider even hibernates under water. When the weather gets cold, it constructs an air bubble in deep water and remains there until spring.

Some invertebrates, such as crabs, survive in wetlands by creating watertight holes in the mud or sand and hide there during high tide. Other species, like the African mangrove snail, feed in the mud and sand when the tide is low. When the tide comes in the snail climbs the mangrove trees to keep from drowning.

Common invertebrates

Perhaps the most well-known and unpopular wetland invertebrate is the mosquito. Mosquitoes breed in shallow wetland waters. In their larval form, they have tubes in their abdomens that stick out of the water, allowing them to breathe. Larvae are often eaten by frogs, fish, and aquatic insects. Those that survive face being eaten by bats, sprayed with pesticides, and swatted by humans. In spite of these hazardous conditions, mosquitoes in large numbers are responsible for diseases in both humans and animals.

The Marsh Treader

The marsh treader is an insect that can be found walking very slowly across the surface of marsh water. It has a long, skinny body about 0.3 inches (8 millimeters) in length. Its legs are as fine as threads and its body is covered with velvety hairs. As it moves across the water, it searches for food. Mosquito larvae are its favorite meal.

Food

Insects may feed underwater as well as on the surface. The milkweed beetle feeds on insects found on wetland plants, while the diving beetle’s diet includes tadpoles and small fish. The dragonfly larva eats tiny floating organisms and water fleas. The larva of a certain species of caddisfly weaves a silk net under the water in which to catch floating algae.

Some snails are plant feeders, while others eat the eggs and larvae of other invertebrates, or even decaying matter. Crabs are often omnivorous, meaning they eat both plants and animals.

Reproduction

Most invertebrates are insects, which have a four-part life cycle. The first stage is the egg. The second stage is the larva, which may be divided into several steps as the insect increases in size, between which there is a shedding of the outer casing or skin. The third stage is the pupal stage, during which the insect lives in yet another protective casing. Finally, the adult emerges. Some wetland dragonflies lay their eggs in the tissues of submerged plants. The insects remain in the water as larvae. As they mature, they move to dry land.

Amphibians

More than 190 species of amphibians are found in wet-lands. Amphibians are vertebrates, which means they have a backbone. There are two kinds of amphibians, those with tails, like salamanders and newts, and those without tails, like toads and frogs.

Amphibians live at least part of their lives in water and are found in primarily freshwater environments. Most are found in warm, moist regions and in a few temperate zones. Because amphibians breathe through their skin, they must remain close to water so they can stay moist. Only moist skin can absorb oxygen. If they are dry for too long they will die. Their lower layer of skin, called the dermis, helps them to stay moist by producing mucous, a thick fluid that moistens and protects the body.

Amphibians are cold-blooded animals, which means their body temperature is about the same temperature as their environment. They need warmth and energy from the sun in order to be active. As temperatures grow cooler, they slow down and seek shelter. In cold or temperate

The Salamander that Never Grows Up

The axolotl, a type of salamander found in freshwater wetlands in Mexico and the western United States, spends its entire life as a tadpole. It can reach a size of 10 inches (25 centimeters) and is able to reproduce, but it never matures, so it never leaves the water. Scientists have determined that the diet of these salamanders is lacking the chemical iodine, which is in short supply in many parts of the world. This shortage is the reason why iodized table salt is used in most homes. Iodine has been added as an essential nutrient.

regions, some amphibians hibernate (become inactive) during the winter, hiding in mud or trees. When the weather gets too hot, they go through another period of inactivity called estivation.

Common amphibians

The most common wetland amphibians are salamanders, frogs, and toads. Frogs and toads are found all over the world, at all altitudes, and in both fresh and salt water.

Frog

A frog spends half its life in the water and half out of it. Frogs can lay up to 3,000 eggs, which float beneath the water’s surface. The eggs hatch into tadpoles (larvae), which swim and breathe through gills, like those on a fish. The larvae feed on small plants and animals in the water. As they mature, legs and lungs develop, which they will need on land.

Adult frogs feed mainly on insects, especially mosquitoes, but bullfrogs have been known to eat birds and snakes. In the food web they, in turn, become meals for herons, raccoons, and other wetland animals.

Frogs are considered bio-indicators. This means that when many frogs are sick their entire environment may be in trouble. If they disappear from a habitat or if they do not sing, the area may be polluted and its resources may be dwindling. Frogs are totally absent from some wet-lands in the United States, indicating their environment was no longer a healthy place for them to live.

Food

In their larval form, amphibians are usually herbivorous (plant-eating). Adult amphibians are usually carnivorous (meat-eating), feeding on insects, slugs, and worms. Salamanders that live in the water suck prey into their mouths. Those that live on land have long, sticky tongues that capture food.

Reproduction

Most frogs and toads lay many tiny eggs. Some are held together in a jellylike substance. As the female lays her eggs in the water, the male releases sperm, which is carried to the eggs by the water. Most salamanders and newts lay eggs that have been fertilized internally (within the female).

Reptiles

Reptiles are cold-blooded vertebrates that depend on the environment for warmth. Thousands of species of reptiles live in the temperate and tropical wetlands of the world. They include snakes, lizards, turtles, and crocodiles. Reptiles are more active when the weather and water temperature become warmer. Unlike amphibians, reptiles have skin that is waterproof, so they do not dry out. This allows them more freedom to move away from the wet areas.

Because they are so sensitive to their environment, reptiles often go through a period of hibernation in cold weather. Turtles bury themselves in the wetland mud. They barely breathe, and their energy comes from stored body fat. When the weather warms in spring, they come out of hibernation and become active. At the other extreme, when the weather becomes very hot and dry, some reptiles go through estivation, another inactive period.

Common reptiles

Two well-known and dangerous wetland reptiles are the crocodile and the cottonmouth snake.

The Web of Life: Keystone Species

Species interact with one another in many ways. Those that play an important role in the survival of others are called keystone species. In the wetlands, a keystone species is the alligator, which lives in southern marshes such as the Florida Everglades.

Wetlands often dry up if rainfall is low. Alligators then dig holes with their powerful tails and bodies. Water collects in these holes and helps alligators, as well as birds, fish, frogs, turtles, and other marsh animals, survive during dry periods.

Crocodile

Crocodiles are found in warmer parts of North and South America, Africa, Australia, and Southeast Asia. They have inhabited Earth for more than 170,000,000 years. Their long survival may be due in part to the fact that they will eat almost anything or anyone. Crocodiles are responsible for killing at least ten humans every day in Africa, and a large crocodile will attack a 4,000-pound (1,816-kilogram) adult rhinoceros if given the chance. A crocodile’s teeth are rounded and made for holding, not cutting, and it first tries to swallow its prey whole. If the prey is too large, the crocodile pulls it underwater and stashes it where it can decay. When the meat is soft, the crocodile rips off a piece at a time.

The largest living crocodile officially recorded was 20.3 feet (6.2 meters) long. A crocodile continues to grow throughout its life, reaching average ages of 60-70 years; the oldest known crocodile was 115 years old. Their speed out of the water over short distances may be more than 35 miles (56 kilometers) per hour. By contrast, a very fast human may run 25 miles (40 kilometers) per hour over the same distance.

Cottonmouth snake

The cottonmouth snake inhabits marshes and swamps in the south and southeastern United States. A thick-bodied snake, it spends most of its life in or near water. It is active at night, when it preys on amphibians, fish, snakes, and birds. Its venom is extremely poisonous.

Food

Some wetland reptiles, such as the dice snake, are carnivores that eat frogs, small fish, and crayfish. The pond turtle, which inhabits tropical swamps, is an omnivore. When it is young it feeds on insects, crustaceans, mollusks, and tadpoles. As an adult, it eats primarily wetland plants.

Reproduction

The eggs of lizards, alligators, and turtles are either hard or rubbery and do not dry out easily. Most are buried in the warm ground, which helps them hatch. In a few species of lizards and snakes the young develop inside the female’s body until birth.

The dice snake lays it eggs on land, close to the water. Crocodiles and alligators keep eggs in warm nests, which can be simple holes in the ground or constructions above the ground made from leaves and branches.

Fish

Like amphibians and reptiles, fish are cold-blooded vertebrates. They use fins for swimming and gills for breathing. Two-thirds of all fish used for human food depend on wetlands during some part of their lives. Most commercial game fish breed and raise their young in marshes and estuaries. When the wetlands are not healthy, the fish die, and the commercial and recreational fishing industries suffer.

Common fish

Fish that commonly rely on coastal wetlands are striped bass, sea trout, African lungfish, mudskippers, and flounder. Brackish marshes, which contain both salt and fresh water, support sole, sardines, and common mackerel.

African lungfish

The African lungfish, which lives in pools surrounded by swampland, has adapted to the wet/dry cycle of wetlands. When there is plenty of water, the fish breathes through its gills. In the dry season, when the water disappears, the fish burrows into the mud and seals itself into a moist cocoon, breathing through special pouches on its underside. It can remain inactive in its cocoon for months or even years.

Mudskipper

Also well adapted to life in the wetland is the mud-skipper, found in coastal areas of Bangladesh. This fish usually lives out of the water on exposed mud at low tides. Mudskippers breathe air through membranes at the back of their throats. Enlarged gill chambers hold a lot of water to help them remain on land for long periods. They keep water in their mouths, which they swish over their eyes and skin to help them stay wet. They feed on crabs that are easily caught during low tide.

Food

Some fish eat plants while others depend upon insects, worms, crustaceans, or smaller fish. Some fish may simply grab an insect from the surface of the water or use a more elaborate scheme. The archerfish, for example, has grooves in the top of its mouth that lets it spit water at its prey. The force of the spit knocks the insect off its perch and into the water, where it is quickly eaten. Archerfish are found in the swamps of southeast Asia.

Reproduction

Fish that breed in wetlands include flounder, sea trout, striped bass, and carp. Some European carp live in rivers and move to the floodplains during spawning (breeding) season. Others live in the ocean and spawn in mudflats, marshes, or mangrove swamps.

Birds

Many different species of birds live in or near wetlands. These include many varieties of wading birds, waterfowl, shore birds, and perching birds. One of the special adaptations of birds to wetlands is their bill. Some bills, like those of the egret, are shaped like daggers for

stabbing prey such as frogs and fish. Other bills, like those of the spoonbill, are designed to root through mud in search of food.

Wetlands provide a variety of hiding places where birds can build nests and protect their young. Dense underbrush or hollows in the ground are good hiding places, especially when nests are made from reeds, flowers, and grasses, which help them blend into their surroundings. Wood ducks build their nests in hollow cavities in trees lining the wetland shores.

Common birds

Birds found in wetland environments can be grouped as wading birds, shorebirds, waterfowl, and perching birds.

Wading birds

Wading birds, such as herons and egrets, have long legs for wading through the shallow water. They have wide feet, long necks, and long bills that are used for nabbing fish, snakes, and other food. Herons and egrets are the most common in freshwater marshes of North America. The great blue heron stands 4 feet (1.2 meters) tall. This is the tallest recorded wading bird in North America.

Shorebirds

Shorebirds feed or nest along the banks of wetlands and prefer shallow water. Their feet are adapted for moving in water, and some have long, widely spread toes to prevent them from sinking in the mud.

The bills of shorebirds are designed to help them find food. The ruddy turnstone, for example, has a short, flattened, upturned bill, which helps it sift through mud or overturn pebbles and shells. A favorite food of the oystercatcher is the mussel. Each young oystercatcher learns from its parents a technique for opening the mussel shells to get at the meat. Some birds hammer a hole in the shell with their bills, and others prop the shells at an angle so they can pry them open. It may take the birds several years of practice to get the technique just right.

There are more than 200 species of shorebirds dependent on wetland habitats. These include sandpipers, which are found in marshes, wet woodlands, and on inland ponds, lakes, and rivers.

Waterfowl

Waterfowl are birds that spend most of the time on water, such as ducks, geese, and swans. Their legs are closer to the rear of their bodies than those of most birds, which is good for swimming, but awkward for walking. Their bills are designed for grabbing wetland vegetation, such as sedges and grasses, on which they feed.

Perching birds

Perching birds can be found living along wetland areas where food and shelter are readily available. They are land birds, with feet designed for perching. Their feet usually have three long toes in the front and one in the back. The barred owl is commonly found in swamps, while red-winged blackbirds live in cattail marshes. Bogs are home to golden plovers, skylarks, and meadow pipits.

Food

Plants and small animals in wetlands provide a ready food source for birds. Some birds feed on vegetation, while others are predatory. The marsh harrier, for example, feeds on mussels, small fish, or insects and their larvae. Herons and egrets feed on fish, frogs, and snakes.

Reproduction

All birds reproduce by laying eggs. Most male birds are brightly colored and sing to attract the attention of females. After mating, female birds lay their eggs in nests made out of many different materials. These nests may be found in a variety of places throughout the wetland area. Different species of birds lay varying numbers of eggs. The tufted duck, for example, lays six to fourteen eggs that hatch in less than a month. The ducklings begin to swim within days.

Mammals

Mammals are warm-blooded vertebrates that are covered with at least some hair and bear live young nursed with milk. Aquatic mammals, such as muskrats, have waterproof fur that helps them blend into their surroundings and webbed toes for better swimming. Some of these mammals live permanently in wetlands and others, such as raccoons, visit for food, water, and shelter during part of their lives.

The Duck that Saved Wetlands

The Federal Duck Stamp Program began in 1934 when the U.S. Congress passed the Migratory Bird Hunting Stamp Act. The act required waterfowl hunters to purchase and carry Federal Duck Stamps that are attached to a hunting license or other document. The money was used to buy or lease waterfowl habitats from their owners and designate them as restricted areas. This helped save millions of acres of wetlands.

Over the years, efforts have also included saving wetland species that were declining in numbers, such as wood ducks, canvasback ducks, and pintail ducks. The program helps endangered species that rely on wetlands for food and shelter.

Anyone can own Federal Duck Stamps. State, international, and junior stamps are available. A duck stamp provides free admission to all National Wildlife Refuges where entrance fees are charged. To learn more about the duck stamps and to see pictures of them, visit http://www.nationalwildlife.com.

Common mammals

American beavers are well-adapted to the wet-land environment. They have webbed feet for powerful swimming

and warm, waterproof fur. Other mammals found in wetlands include the mink, the water shrew, and the Australian platypus. The sitatunga, a type of antelope, lives near swamps in central and east Africa. It feeds on emergent wetland plants.

Red deer

Although peatlands generally do not support many species of animals, red deer live in the bogs. At 5 feet (1.5 meters) tall, it is the largest land mammal found in Ireland. It can be seen rolling in the peat in order to get rid of parasites and insects.

Muskrat

Muskrats resemble beavers. They are heavy-bodied rodents about 12 inches (30 centimeters) long, not including the long tail. They are native to North America and common to marshes all over the country. Their hind feet are webbed for swimming and they can often be seen floating on the water’s surface. Marsh plants such as sedges, reeds, and the roots of water plants provide most of their diet.

Muskrats build dome-shaped houses in water. They pile up mud, cattails, and other plants until the mound rises above the water’s surface. Tunnels lead into the mound where one or more rooms are hollowed out above the water’s surface.

These mammals are hunted for their fur, which is brown and consists of soft underfur and a dense coat. They are also sold as food, often labeled as “marsh rabbit.”

Food

Some aquatic mammals, like the otter, are carnivores, eating rabbits, birds, and fish. Muskrats are omnivores, eating both animals, such as mussels, and plants, such as cattails. Beavers are herbivorous and eat trees, weeds, and other plants.

Reproduction

Mammals give birth to live young that have developed inside the female’s body. Some mammals are helpless at birth while others are able to walk and even run immediately. Some are born with fur and with their eyes and ears open. Others, like the muskrat, are born hairless and blind. After about three weeks young muskrats are able to see and swim.

Endangered species

Over half of the endangered or threatened fish and other wildlife in the United States (about 240 species altogether) rely partly on wetlands for food, water, shelter, or a place to reproduce. Over one-third of these live only in wetlands.

In North America, endangered species include the whooping crane and the manatee. The whooping crane lives in coastal swamps and feeds on roots and small reptiles. It has been threatened by hunting, pollution, and dredging (dragging a net along the bottom of a body of water to gather shellfish or plant specimens).

The manatee is a slow-moving, seal-like animal. Manatees live in shallow coastal wetlands in the Caribbean, the Amazon, and Africa. They have become endangered because of overhunting, being caught and strangled in fishing nets, or being killed by boat propellers. Pollution has disrupted their habitats and food sources.

In Ireland, the Greenland white-fronted goose, which relies on bogs for feeding and breeding, is endangered because many bogs have disappeared.

The Swimming Rabbit

The North American swamp rabbit has broad, flat feet so that it can move easily over wet, marshy soil. It can swim, and often escapes danger by staying submerged with only the tip of its nose exposed to the air in order to breathe.

Human Life

After 13000 BC, wetlands played an important role in early civilizations. For prehistoric communities throughout the world they provided food, water, and materials for clothing, shelter, and tools. Wetlands are able to reveal many of these ancient civilizations’ secrets to scientists. Bodies of animals and humans, and artifacts (objects made by humans, including tools, weapons, jars, and clothing) have been well preserved in some wetlands and give information about how ancient people lived. Evidence of these ancient communities has been found in bogs. Conditions in bogs are excellent for preserving artifacts and bodies.

Impact of wetlands on human life

Wetlands have had an affect on the supply of food and water, on shelter, and on other resources.

The Bog People

Organic materials in peat bogs absorb and hold large amounts of water like a sponge. Bog soils are extremely acidic and have little oxygen. Because of these factors, decomposition takes place very slowly. Entire trees, animals, and even human bodies have been preserved for centuries.

The remains of more than 2,000 humans have been found in bogs, primarily in northwestern Europe. The bodies are in various stages of preservation, from skeletons to those with flesh intact. Sometimes only body parts such as heads or limbs are found. Often the skin has darkened and the hair has turned red from peat acids. The bodies found in Europe range in age from about 1,500 to 3,000 years old. The body of a woman, known as the Koelbjerg Woman, was found in Denmark and is believed to be 10,000 years old.

Many of these people appear to have died violent deaths. Perhaps they were killed as a punishment for a crime or were the victims of human sacrifice. Their deaths may have taken place at the bog because it was so isolated.

At a bog in Windover, Florida, 160 bodies have been found that are about 7,000 years old. Buried with them are food, tools, clothes, and weapons. Many of these items were made from wetland plants and from the bones of wetland animals.

Food and water

Wetlands are a source of water for drinking and crops. Areas near wetlands continue to provide food in a variety of ways for tribal cultures in Asia and Africa and for urban peoples elsewhere. Since wetlands are a habitat for much wildlife, hunting and fishing are common there.

Cattle can be raised near wetlands because water and grazing land are available. Crops such as sorghum (a cereal grain native to Africa and Asia) are commonly grown in wetland areas. Grain sorghums, such as milo, kafir, and durra, have adapted to the extremes of the wet/dry cycle of the wetland and are among the most drought-tolerant grains. Millions of people in China, India, and Africa rely on sorghum as a food staple. In the United States, sorghum is used mostly as livestock feed.

Besides sorghum, American farmers use wetland plants, such as marsh grass, reeds, and sedges, for feeding livestock. Wetlands are an excellent place to grow rice, which is a major food source for much of the world’s population.

Shelter

Materials for dwellings are available from wetland sources. Roofs made from reeds are used on huts in Egypt and in stilt houses in Indonesia to keep the occupants cool and dry. A tightly woven reed roof can last for forty years. House frames are constructed from the timber of

Houses Without Walls

The Seminoles, a Native American people who once lived in the Florida Everglades, built homes with no walls. Called a chikee, the home was built on a platform, had a log framework, and a thatched reed roof. The absence of walls provided ventilation in the warm climate.

mangrove, and palm trees. Wetland sediments, such as clay and mud, may be used to produce bricks that are used for walls.

Other resources

Wetlands provide other resources that humans rely on besides building materials. For example, dried peat is used in homes for heat and to fuel electric generators in countries such as Ireland, where coal is scarce. Peat is a source of protein for livestock feed, and chemically processed peat is used as a base for polishes and waxes. In horticulture, peat moss is used as ground cover, a soil conditioner, and a growing medium. Peat is also found in medicinal baths and cosmetics.

There are at least 120 distinct medicinal substances derived (made) from wetland plants. Wetland soils are sources of gravel and phosphate. Phosphate is used as a raw material for making fertilizers, chemicals, and other commercial products.

Wetlands prevent loss of human life and property during floods because they absorb and store water. The riparian wetlands along the Mississippi River once stored sixty days of floodwater. Since most of these wetlands have been filled or drained, they now only store twelve days of floodwater.

Impact of humans on wetlands

The important role of the wetland for plant and animal communities and for the environment in general has not always been understood. For more than 2,000 years, people in different countries have been draining wetlands to get rid of mosquitoes and disease, to increase land for farming, and to make room for development. By 1990, more than half of the wetlands in the United States were destroyed.

As the value of wetlands becomes more recognized, government agencies, such as the U.S. Department of the Interior and U.S. Fish and Wildlife Service, as well as environmental groups, are working to preserve existing wetlands and to create new ones. In 1989, U.S. president George Bush, asked that the United States work toward the goal of no net loss of wetlands. This means that if a natural wetland is destroyed by development, an artificial one must be built to replace it. As of July 1998, there were 97,000,000 acres (39,000,000 hectares) of artificial wetlands in the United States. In 1998, the Clinton administration issued an

An Earth-Friendly Architect

Architect James Cutler of Seattle, Washington, believes that the environment should be preserved when designing and building houses. He has gone to extremes to save the landscape, including building houses on stilts and placing sidewalks over the tops of forests. Cutler designed a home for Microsoft Chairman Bill Gates, where he reestablished wetlands on the property.

initiative calling for a net gain of 100,000 acres (40,500 hectares) of wetlands per year beginning in 2005.

The Convention on Internationally Important Wetlands was signed by representatives of many nations in Ramsar, Iran, in 1971. Commonly known as the Ramsar Convention, it is an intergovernmental treaty that provides the framework for national action and international cooperation for the conservation and wise use of wetlands and their resources.

Use of plants and animals

When animals and plants are overharvested they may become endangered. Overharvesting means they are used up and destroyed at a faster rate than they can reproduce. When this happens, wetland, timber, fuel, medicines, and sources of food for humans and animals are all lost.

Use of natural resources

The two primary resources found in wetlands are water and peat. Wetlands often act as part of the ground-water system. When they are lost, the supply of drinking water may be affected.

It takes ten years to form less than half an inch of peat, and its overuse has caused significant peatland losses. Western European peat mining companies are rapidly using up local areas of peat and expanding their mining operations into eastern European countries. All natural peatlands in the Netherlands have been destroyed. Switzerland and Germany each have only 1,250 acres (500 hectares) of peatland remaining.

Quality of the environment

Wetlands are endangered by industrial and municipal (city) contaminants, by the accumulation of toxic chemicals, and from acid rain.

Acid rain is a type of air pollution especially dangerous to wetlands. It forms when industrial pollutants such as sulfur or nitrogen combine with moisture in the atmosphere and form sulfuric or nitric acids. These acids can be carried long distances by the wind before they fall either as dry deposits or in the form of rain or snow. Acid rain can significantly damage both plant and animal life. It is especially devastating to wetland amphibians such as salamanders, because it prevents their eggs from maturing.

Mining for minerals near a wetland can have a negative impact on the biome. Mercury, a poisonous liquid metal used in gold mining operations, often contaminates wetlands close to the mines. Mining operations also require large amounts of water, and nearby wetlands may be drained.

The world’s climate may be growing warmer because of human activity. As polar ice caps melt, there is a rise in sea level. As this happens, more salt water floods into coastal wetlands and increases the salinity not only of the wetlands, but of rivers, bays, and water supplies beneath the ground. As these habitats change, animal and plant life are affected, and some wetlands may be destroyed.

Artificial wetlands

Artificial wetlands are those created by humans. Creating a wetland is very difficult; all the right conditions need to be met, including a water source and nutrient rich soil that contains a lot of water but not much oxygen. In Arizona, there are twenty-six artificial wetlands operational with twenty-four others under construction or awaiting approval.

An artificial wetland that works well and is extremely valuable worldwide is a rice paddy. A rice paddy is simply a field that is flooded for the purpose of growing rice, a food staple for about three billion people—nearly one half of the world’s population. Some are flooded naturally, by monsoon (tropical) rains or overflowing rivers. Others are flooded by irrigation (watering). Mud dams and waterwheels are built to bring in and hold the water level at approximately 4 to 6 inches (10 to 15 centimeters) while the rice grows. Ninety percent of rice paddies are in Asia, especially China and India. Some rice is also grown in Europe and the United States.

Artificial wetlands are found on the Arabian Peninsula where they are used for water storage and sewage treatment. Other human-made wet-lands have been created as winter homes for migrating waterfowl.

Adopt A Wetland

Both the federal government and individual states are working to protect wetlands. Some states sponsor “Adopt a Wetland” programs, in which groups of people agree to help support their local wetlands in a variety of ways, such as picking up litter. For information about adopting a wetland, contact the U. S. Environmental Protection Agency, Public Information Center, (202) 260-7756 or (202) 260-2080.

Marshes Clean Up Messes

A lot of contaminants seep into the environment every day from oil spills, sewage treatment plants, industrial waste, and old mines. In some areas, phytoremediation (fi-toh-rih-mee-dee-AY-shun) is being used to clean up these messes. (Phyto is a Greek word for plant and remediation means to make things right.) Phytoremediation uses plants to absorb pollutants.

One type of phytoremediation involves creating an artificial marsh containing cattails and water lilies. These wetland plants are able to absorb some water pollutants. Poplar trees can clean up water polluted with oil, and sunflowers are used to help clean up radioactive materials in the soil. Sunflowers are used near the Chernobyl nuclear power station in Pryp’yat near Kiev in the Ukraine. The power station exploded in 1986, releasing radioactive waste into the environment.

Native peoples

The Marsh Arabs of Iraq and the Nilotic peoples of Africa live in or near wet-lands that provide almost all of the resources they need.

Marsh Arabs of Iraq

The Mesopotamian wetland lies between the Tigris and Euphrates Rivers in southern Iraq. At almost 8,000 square miles (20,000 square kilometers), it is one of the largest wetlands in the world. The Marsh Arabs, or Ma’dan, have lived there for more than 6,000 years. The water there is clean, calm, and fairly shallow—about 8 feet (2.4 meters) deep.

The Marsh Arabs’ houses are made of reeds and built on islands that they make. To construct the islands, they create a fence from reeds and partially submerge it. Then they fill the area inside the fence with cut rushes, add layers of mud, and stamp it all down. When the pile reaches the water’s surface, they fold the top of the fence onto the pile and add more reeds to finish it. The completed island is big enough not only for the family to build a house and live on, but for their cattle as well.

Isolation from the outside world has allowed the Marsh Arabs’ way of life to remain the same for hundreds of years. Daily life consists of fishing, buffalo herding, and growing rice. Reeds are gathered every day to feed the buffalo. Transportation from house to house or to other villages is by means of small canoes called mashhufs.

Survival of the Marsh Arabs is threatened by irrigation practices, which have drawn water from their wetlands. Some of the marshes have already been drained for agricultural use and oil exploration.

Nilotic Peoples

Nilotic peoples live near the Nile River or in the Nile Valley in Africa. Two Nilotic tribes, the Dinka and the Nuer, live in southern Sudan. This area is a rich floodplain, and during the wet season, from July through October, the people live on high ground in permanent villages. From December through April, when the floodwater recedes, they move to the flood-plains. There, the Dinka build temporary villages along the banks of the Nile River. Their homes, made from reeds and grasses, are circular at the base and come to a point at the top, much like a teepee. Their neighboring tribe, the Nuer, lives in a similar fashion but in the marsh, savanna (grass-land), and swamp areas.

Wetland grasses and plants grow in the floodplain after the waters recede. The grasses provide food for cattle and attract wildlife, which is often hunted for food. Nilotic tribes fish, hunt, and grow some grains. The Dinka use their cattle for meat and milk, but the Nuer eat cattle only during religious ceremonies. For them, cattle represent wealth and are used for bridal dowries (gifts) and to sell. Animal hides are made into clothing and bedding, and dried cattle dung (waste) is used for fuel.

The Food Web

The transfer of energy from organism to organism forms a series called a food chain. All the possible feeding relationships that exist in a biome make up its food web. In the wetland, as elsewhere, the food web consists of producers, consumers, and decomposers. These three types of organisms transfer energy within the wetland environment.

At the bottom of the food chain are the producers, such as photo-synthesizing plants and algae, which use energy from the sun to produce sugars and starch from carbon dioxide and water. The shallow wetland water lets in lots of sunlight, which helps these organisms grow.

Primary producers are eaten by primary consumers such as the larval forms of frogs and toads, and larger animals such as shrimp and snails. Other primary consumers, such as small aquatic insects, shellfish, and small fish, feed on plant materials.

Primary consumers are food for predators such as larger fish, reptiles, amphibians, birds, and mammals, which are called secondary consumers. Tertiary consumers are the predators, such as owls, coyotes, and humans, that prey on both primary and secondary consumers.

The decomposers feed on dead organic matter and include fungi, bacteria, and crabs.

Spotlight on Wetlands

The Florida Everglades

The Florida Everglades, lying within the sub-tropical zone near the tropics, is one of the largest freshwater marshes in the world, stretching from Lake Okeechobee 100 miles (160 kilometers) south to Florida Bay. Within its boundaries are freshwater swamps and coastal (saltwater) mangrove swamps. In the northern portion of the Everglades is Big Cypress Swamp. This swamp covers 1,500 square miles (4,000 square kilometers) and gets its name from the many tall bald cypress trees that live there.

The Florida Everglades

Location: Southern Florida

Area: Approximately 1,506,539 acres (606,688 hectares)

Classification: Freshwater marsh, freshwater swamp, and saltwater swamp

The Everglades were formed during the last ice age, which ended about 10,000 years ago. During this period, glaciers melted and sea level was raised, which flooded the area and turned it into a wetland. Under the water and soil is a porous limestone rock formed during the last glacial period. This type of rock contains shells and skeletons of animals deposited in the sea. Hummocks (rounded hills or ridges) have formed in some areas, and hardwood trees can grow there. Otherwise, the terrain is flat.

The subtropical climate of the Everglades is mild, with temperatures ranging from 73° to 95°F (25° to 35°C) in the summer. Winters are mild, with an average high of 77°F (25°C) and a low of 53°F (12°C). The rains occur from June to October, with an annual accumulation of about 55 inches (140 centimeters). The region is often hit by severe tropical storms.

The grassy waters of the Everglades are actually very shallow, ranging from about 6 inches (15 centimeters) to 3 feet (94 centimeters) deep. They cover about 4,000 square miles (10,300 square kilometers). Water comes from rainfall and overflows from Lake Okeechobee.

Much of the Everglades are covered with sawgrass, a type of sedge. Tropical plants, such as ferns, orchids, and mosses, grow in freshwater areas. Saltwater aquatic plants include lilies and bladderworts. Cypresses, palms, live oaks, and pines grow on the hummocks.

Among the invertebrates, the Liguus tree snail can be found living on the hummocks, and Everglades reptiles include turtles, king snakes, water moccasins, and rattlesnakes. Alligators live in freshwater areas while American crocodiles live saltwater swamps.

Tourists are attracted by the bird life in the Everglades. Herons, egrets, spoonbills, ibises, eagles, and kites are a few of the birds in the area. The Everglades kite, a tropical bird of prey, has been named after the region. Mammals include white tailed deer, cougars, bobcats, black bears, and otters.

Many attempts have been made to drain the Everglades so the land could be used for farming and development. Drainage projects began in the early 1900s. Consequently, about 50 percent of the wetlands have been altered. Due to agriculture and development, only about 27 percent of the original area has been preserved as the Everglades National Park.

Draining the area has caused a loss of animal and plant life. Endangered species include the manatee, the round-tailed muskrat, and the mangrove fox squirrel. Early in the twentieth century, plume hunters nearly wiped out egrets and spoonbills for their feathers, which were used extensively as decorations on women’s hats.

The introduction of non-native species of plants is also a threat. The Australian melaleuca tree and the Brazilian pepper plant have spread throughout the area, using up water supplies and choking native plants.

Agriculture is the leading economic activity in the region. In the area south of Lake Okeechobee, farmers raise sugarcane, fruit, and vegetables, which are shipped north. Sport fishing, boating, hunting, and camping are popular in the area.

The Seminole Indians, who were driven out of the Okefenokee Swamp in northern Florida by American troops during the nineteenth century, found a safe home in the Everglades. They planted corn and vegetables and gathered roots and nuts. Fishing and hunting were also sources of food. Throughout the twentieth century, the number of Seminoles living in the area has decreased. Another tribe, the Miccosukee, still live in reservations near the center of the Everglades.

A growing concern for the environment has encouraged protection of the Everglades and its ecosystem. It became a national park in 1947 and is the third largest and the wettest national park in the United States. The park includes 10,000 islands off the Florida coast along the Gulf of Mexico, and more than one million people visit annually.

Okefenokee Swamp

The word “Okefenokee” (oh-kee-fen-OH-kee) is taken from a Timucuan Indian word and means “trembling earth.” This refers to the small bushes and water weeds that float on the swamp’s open water and move when the water is disturbed. The swamp, which is 25 miles (40 kilometers) wide and 38 miles (61 kilometers) long, is one of the oldest and most well-preserved freshwater wetlands in the United States.

Okefenokee Swamp

Location: Southeastern Georgia and northern Florida

Area: 438,000 acres (177,000 hectares)

Classification: Freshwater swamp, bog, marsh

The Okefenokee lies about 50 miles (80 kilometers) inland from the coast of the Atlantic Ocean in Georgia, but a sandy ridge prevents the swamp from draining directly into the ocean. The Suwannee River is the principal outlet of the swamp providing 85 percent drainage into the Gulf of Mexico.

The Okefenokee was formed almost 250,000 years ago when the waters of the Atlantic Ocean covered the area. When the ocean receded, some salt water was trapped in depressions in the ground. Over thousands of years, plants grew and filled the wetland. As they decayed, they turned into peat, which now forms the swamp floor. The peat is as deep as 15 feet (4.6 meters) in places.

Freshwater lakes, wet savannas (grasslands with scattered trees), cypress woods, hummocks, open grassy spaces, peat bog islands, and thick brush are also found in the Okefenokee. Many channels form a maze through the area. About 60 inches (152 centimeters) of rain falls annually.

The Okefenokee supports 621 species of plants, including rare orchids and lilies. The insectivorous pitcher plant, maiden cane, floating hearts, and golden club all add color. Freshwater regions support sphagnum moss, ferns, and rushes. Tupelo trees and giant bald cypress trees covered with Spanish moss add an eerie quality.

Insects, such as the mosquito and the yellow fly, are abundant, and 37 species of amphibians make the Okefenokee their home. At least 64 species of reptiles live here, including 5 kinds of poisonous snakes, and more than 10,000 alligators. Considered “kings” of the swamp, alligators are a major tourist attraction. About 40 species of fish live in the swamp, including bluegill, warmouth, golden shiners, and pumpkinseed sunfish. These fish have adapted to life in the acidic water. They are often dark with yellow undersides and they can see in low light.

The Okefenokee is home to 233 species of birds including the white ibis, the sandhill crane, the wood duck, the great blue heron, and the barred owl.

Bears, bobcats, deer, foxes, and raccoons live in the forested areas. Approximately thirty species of mammals can be found in the swamp, including the black bear.

The area surrounding the swamp was settled by Europeans in the late 1700s. The Seminoles once lived in the interior, but they were driven out by American troops in 1838.

During the 1800s, developers tried to drain the swamp by building a canal, but found the project larger than anticipated. The project was abandoned in 1893. After the turn of the century, logging companies built railroad tracks through the swamp; as a result 400,000,000 feet (120,000,000 meters) of timber, mostly cypress were cut down. In 1937, U.S. president Franklin Roosevelt (1882–1945) protected about 629 square miles (1,630 square kilometers) of the Okefenokee by designating it the Okefenokee National Wildlife Refuge. Despite these actions, the swamp continues to be threatened by developers, including those who want to mine titanium ore on its eastern rim. Due to public and government opposition, the mining project was terminated.

Fire is a natural part of the swamp’s ecosystem, which can occur as infrequently as every 30-50 years. The two most recent fires occurred in May 2002 and May 2007.

The Okefenokee offers walking trails for tourists and 120 miles (193 kilometers) of water trails that can be explored by canoe.

The Mekong Delta

The Mekong Delta extends from Phnom Penh, the capital of Kampuchea province in Vietnam, to the coastline bordering the South China Sea. The Mekong River, the longest in Southeast Asia, divides at Phnom Penh into two branches. As the branches pass through the delta they form nine channels. The name Mekong means “Nine Dragons” and refers to these channels.

The Mekong Delta

Location: Vietnam

Area: 12,237 acres (49,712 square kilometers)

Classification: Freshwater swamp and saltwater swamp

The delta, which supports 15,000,000 Vietnamese, forms a 13,600,000 acre (5,500,000 hectares) triangular area including floodplain, freshwater, and saltwater swamps. Mangrove and melaleuca forests cover the remaining area.

Most of the delta is less than 16 feet (5 meters) above sea level. From May to October the area experiences heavy rains, ranging from 59 to 92 inches (150 to 235 centimeters). The average temperature is about 79°F (26°C), and the climate is very humid.

The Mekong Delta supports 35 species of reptiles, including crocodiles and the endangered river terrapin (a type of turtle), and 260 species of fish, many of which are sold commercially. Herons, egrets, ibises, and storks nest in the delta’s forested areas. Mammals include otters and fishing cats.

The delta is rich in agricultural produce, fish, and waterfowl. At one time it yielded 26 tons (23.5 metric tons) of fish per square mile. About half of the delta is devoted to rice paddies, which yield about 6,500,000 tons (5,900,000 metric tons) of rice each year.

During the Vietnam War (1959–1975), the Mekong Delta was seriously damaged when Agent Orange and other defoliants (chemicals that cause leaves to fall off plants and trees) destroyed over 50 percent of the mangrove forests. The object was to remove any hiding places used by the enemy, but Agent Orange also caused skin diseases, cancer, and birth defects. One-fifth of the country’s farmland was destroyed by direct bombing and machines used to clear land. The melaleuca forests were burned with Napalm, another chemical weapon, and almost destroyed. These chemicals made much of the soil infertile.

Of the 386 bird species supported by the Mekong Delta, 92 are waterfowl. The eastern Sarus crane, an endangered bird, disappeared during the war but has since returned. The giant ibis, the white-shouldered ibis, and the white-winged wood duck, all endangered, have not been seen here since 1980.

Hydroelectric dams, built for generating electricity, have a negative affect on the ecosystem. The dams reduce flooding, which decreases the freshwater flow to wetlands. Spawning areas for fish are declining and mangrove forests are being converted to artificial ponds by the farmed shrimp industry.

The Great Dismal Swamp

The Great Dismal Swamp is a freshwater wetland located in southeast Virginia and northeast North Carolina. Its soil contains few minerals and nutrients. Drainage is poor and the soil is saturated and acidic. In this environment, decomposition is slow and peat accumulates over time.

The Great Dismal Swamp

Location: North Carolina and Virginia

Area: 106,716 acres (42,686 hectares)

Classification: Peat bog and freshwater swamp

The fungus called armillaria, which grows on rotten wood in the swamp, gives off a luminescence (glow) called foxfire. Broad-leaved shrubs such as hollies and bayberries are found here. Bald cypress trees survive well in saturated soil and populate the area; some are as old as 1,500 years. Other native trees include the black gum, the juniper, and the white ash.

Seventy-three species of butterflies and more than 97 species of perching birds, including warblers, woodpeckers, and wood ducks, live in this area. Black bears, bobcats, minks, and otters also live in the region.

Many famous Americans were in some way associated with the Great Dismal Swamp. In 1763, U.S. president George Washington (1732–1799) set up a company to drain the swamp for agricultural purposes and to use its lumber. One hundred-forty-five miles of road were constructed to support the logging activities that continued until 1976. The American statesman, Patrick Henry (1736–1799), who participated in the American Revolution, owned land there. The swamp was used by American author Harriet Beecher Stowe (1811–1892) as the setting for her 1856 novel, Dred: A Tale of the Great Dismal Swamp. The forests of the swamp provided refuge to runaway slaves. In 2003, the Great Dismal Swamp became the first National Wildlife Refuge to be officially designated as a link in the Underground Railroad Network to Freedom.

Kakadu National Park

Kakadu National Park is the largest wetland in Australia and is marked by a great diversity in species and habitats. The area includes freshwater wetlands, mangrove swamps, and billabongs. The term billabong comes from an Australian Aboriginal (native) word meaning “dead river,” and describes standing, often stagnant, water near river channels. Billabongs are usually found only in the parts of Australia where the climate is hot and dry and interrupted by occasional flooding.

Kakadu National Park

Location: East of Darwin in the Northern Territory of Australia

Area: 7,700 square miles (20,000 square kilometers)

Classification: Freshwater wetlands, mangrove swamps

Average temperatures are high all year and range from 91°F (33°C) in July to 108°F (42°C) in October. Rivers flooded by January and February rains feed the freshwater areas. The coastal wetlands are fed by tides.

Kakadu includes many acres of forests, sedges, and grasslands. In April and May, when the dry season begins, bush fires destroy old growth and encourage new plant life.

When the thousands of acres of grassland flood during the wet season, plant and animal life abounds. In all, there are more than 200 species of plants, including 22 species of mangrove trees. Water lilies, woolybutt (Eucalyptus miniata), and spear grass, which grows to more than 6 feet (1.8 meters) tall, can all be found. Paperbark trees dominate freshwater swamp areas.

Numerous turtles and both freshwater and saltwater crocodiles live in the shallows. Barramundi fish travel between the waterholes and estuaries, depending on the season. Goannas, a type of monitor lizard, live here.

Millions of water birds live in the park. These include whistling ducks, magpie geese, radjal shelducks, and grey teals. Shorebirds migrate from as far away as the Arctic to winter in the mild climate of Kakadu.

The Australian native people, called Aborigines, once used the park’s wetland plants and animals as a source of food. Aborigines recognized six seasons in the Kakadu region instead of the traditional wet and dry seasons. Disposal of waste from uranium mines on the edge of Kakadu is threatening the area. Other dangers include tourism and the introduction of non-native plants and animals. Para grass, an exotic grass being tested as cattle feed, is currently choking Kakadu’s wetlands. The big-headed ant, a native of Africa, forms huge colonies that wipe out many native ants and other small creatures.

Kushiro Marsh

The Kushiro (koo-SHEE-roh) Marsh is one of the largest and most important natural wetlands in Japan. It is located in a floodplain and contains small freshwater lakes, reed beds, sedge marshes, and peat bogs. About 68,400 acres (27,700 hectares) have been designated as a national wildlife protection area and a national monument.

Kushiro Marsh

Location: The island of Eastern Hokkaido, Japan, along the Kushiro and Akan Rivers

Area: 112 square miles (290 square kilometers)

Classification: Marsh and peat bog

Annual rainfall averages about 44 inches (112 centimeters). The climate is on the cold side with winter temperatures sometimes falling below -4°F (-20°C). The average annual temperature is 42°F (5.6°C) encouraging slow decomposition and peat formation. Spring and summer are also cool.

The floodplain areas support reeds and sedges. The shallow marshes are extremely important for the endangered red-crowned crane, because they provide a place for the birds to breed and winter. More than 100 species of birds use the area, including geese, ducks, and swans. Mammals found in the marsh include the raccoon dog and the red fox. The marsh has an exceptional abundance of dragonflies.

The Llanos

The Llanos (YAH-nos), a Spanish word for “plains,” is a large grassland covering parts of western Venezuela and northeastern Colombia. Within its boundaries is one of the largest wetlands in South America; a combination of rivers, lakes, marshes, swamps, forests, and ponds. It is bordered by the Andes Mountains on the north and west, the Orinoco and Apure Rivers to the east, and the Amazonian wilderness to the south.

The Llanos

Location: Venezuela and Colombia, South America

Area: 220,000 square miles (570,000 square kilometers)

Classification: Riparian wetland and swamp

The Llanos is a temperate area, with year-round average temperatures of 75°F (24°C). Rain falls primarily between April and November, the central plains get about 45 inches (110 centimeters) annually. Areas closer to the Andes Mountains receive about 180 inches (457 centimeters). The summer is very dry. No growth takes place during these months and frequent fires drive animals to areas that are still wet. When the rains come in the winter, the growing season begins.

Although growth is limited by the long dry period, swamp grasses and sedges are common. Carpet grass is able to grow in drier areas. Oak and palm trees are found along the edges of the rivers.

The Llanos provides a habitat for many wading birds such as herons, storks, and ibises. The capybara, the world’s largest rodent, lives in the area. It grows up to 4 feet (1.3 meters) long and weighs as much as 100 pounds (50 kilograms). Armadillos, deer, and anteaters find shelter in the forest and feed in the grasslands. The green anaconda, the largest snake in the world, makes its home in the Llanos.

The most common economic activity is cattle ranching. Since most ranchers use traditional methods, the activity has had little effect on the area.

Okavango Delta

The Okavango Delta is considered an oasis in the Kalahari Desert. As the Okavango River flows from Angola into Botswana, it becomes choked with weeds and spreads out to create one of the world’s largest inland wetlands.

Okavango Delta

Location: Northwest Botswana, Africa

Area: 6,175 square miles (16,000 square kilometers) in the dry season increasing to 8,500 square miles (22,000 square kilometers) in the wet season

Classification: Freshwater marsh and swamp

Annual temperatures range from 21° to 105°F (-6° to 41°C). Average rainfall is about 18 inches (45 centimeters). In February and March, the river overflows and refills the marshes and swamp areas, making them desirable habitats for plants and animals. Water can be as deep as 16 feet (about 5 meters).

Although rainfall can vary, parts of the delta are always wet from flooding. Water lilies and papyrus are abundant.

The delta is home to kingfishers, herons, and water birds such as ducks, geese, and ibises.

When the waters recede, grazing animals arrive. These include antelope, springbok, and lechwe. The lechwe is a semi-aquatic antelope that feeds on grasses in shallow water. It can graze while standing in water up to 20 inches (50 centimeters) deep. Its elongated hooves help it move through the soft mud on the swamp floor.

The Okavango is the only source of permanent surface water for Botswana. This creates industrial and agricultural demands, such as for diamond mining. An area about 695 square miles (1,800 square kilometers) in size has been designated as the Moremi Wildlife Reserve, one of the few protected areas in Africa.

Pripet Marshes

The Pripet Marshes (also spelled Prepay or Pipit) form a very large wetland in Eastern Europe, covering the southern part of Belarus and northern Ukraine. The marshes are located in a forested basin of the Privet River, and the swamp is the largest in Europe.

Pripet Marshes

Location: Southern Belarus and northern Ukraine

Area: Approximately 104,000 square miles (270,000 square kilometers)

Classification: Marsh, bog, and swamp

Formed during the last ice age, which ended about 10,000 years ago, the marshes were filled with sand and gravel left behind as the glaciers melted. The many lakes in the area are in the process of turning into bogs. Sandy lowlands can be found among a maze of rivers, and pine forests and floodplains add to the diversity of the ecosystem. About one-third of the region is forested.

The climate is cool, with winter temperatures ranging from 18° to 25°F (–8° to –4°C). Warmer temperatures are found in and around the marshes. Annual precipitation is 22 to 26 inches (55 to 65 centimeters).

Trees growing here include pine, birch, alder, oak, aspen, white spruce, and hornbeam. Hornbeam is a type of birch that has smooth, gray bark and catkins (drooping scaly flower clusters with no petals).

Many types of birds live in the marsh, including orioles, grouse, woodpeckers, owls, blue tits, and ducks. Mammals include lynxes, wolves, foxes, wild boars, Asian deer, beavers, badgers, and weasels.

Much of the land has been cleared for lumber and agricultural use over the last several hundred years. Large-scale land reclamation (draining swampland to create cropland) in the twentieth century occurred to promote the development of agricultural areas. Crops grown in the area include rye, barley, wheat, flax, potatoes, and vegetables. Grasses used as cattle feed are also grown here.

The Pine Barrens

The Pine Barrens (or Pineland) are located on the outer coastal plain of Long Island and New Jersey, including parts of the Delaware River and the Jersey Shore. Much of the area is open forest broken by marshes, swamps, and bogs. The area was formed during the last Ice Age.

The Pine Barrens

Location: Long Island, New Jersey

Area: Over 1,000,000 acres (400,000 hectares)

Classification: Bog, swamp, and marsh

The northwest part of the Pine Barrens experiences relatively cold winters, with average January temperatures of less than 28°F (–2°C). The southern area is milder, with average winter temperatures above freezing. Summers are hot, with averages for July ranging from about 70°F (21°C) in the northwest to more than 76°F (24°C) in the southwest. Precipitation (rain, sleet, or snow) is evenly distributed throughout the seasons, averaging between 44 and 48 inches (112 and 122 centimeters) annually.

The Pine Barrens are home to about 100 endangered species of plants. Many rare species include the glade cress, great plains ladies-tresses, grooved yellow flax, and some insectivorous plants. Other plants include wild azaleas, purple cone flowers, Indian grasses, and little bluestems. Rhododendrons, honeysuckles, mountain laurels, wintergreens, and cardinal flowers bring color to the area.

The area is dominated by oak and pine trees, which thrive on the well-drained sites. White cedars grow in the poorly drained bogs. Other trees include buckthorns, dogwoods, sugar maples, hemlocks, birches, ashes, and sweet gums.

The endangered Pine Barrens tree frog makes its home in the park, while bears and wildcats can still be found in some of the woodland areas. Deer, opossums, and raccoons are common.

Commercially, the area is valued for its production of blueberries and cranberries, and for tourism.

Designated by Congress in 1978 as the country’s first National Reserve, the Pine Barrens’ natural and cultural resources are now protected.

On May 1, 2007, a flare from an F-16 plane accidentally dropped into the forest during training, resulting in a fire that burned more than 17,000 acres.

Polar Bear Provincial Park

Polar Bear Provincial Park lies along the southern edge of the Arctic region, on the northwest coast of James Bay and the southern coast of Hudson Bay in Ontario, Canada. A true wilderness, it is accessible only by plane or boat. The dominant type of wetland in the park is peatland. Inland areas of the park contain swamps and marshes, while coastal areas contain saltwater marshes.

Polar Bear Provincial Park

Location: Ontario, Canada

Area: 9,300 square miles (24,087 square kilometers)

Classification: Peatland, swamp, freshwater marsh, and saltwater marsh

Many of the wetlands have formed in kettles (depressions in the ground left behind by retreating glaciers). Rain, melted snow, and overflowing rivers contribute to the water supply. As kettle lakes fill in with vegetation, marshes are formed, and coastal marshes have developed with the movement of the tides. The flat-topped ridges that run along the beach, parallel to the coast, help prevent drainage back into the sea.

Because the park lies along the southern edge of the Arctic region, temperatures are cold. Freezing weather prevails for six to eight months. Summers are short with the average temperature between 60° and 70°F (16° and 25°C). Precipitation is usually less than 21 inches (55 centimeters).

Vegetation varies depending on altitude and wetness. In the higher, cooler regions of the park, plant life includes sedges, goose grasses, and flowering saxifrages. Cotton grasses, sedges, and birches grow in the lower areas. In drier places, blueberries, crowberries, and louseworts are found. Salt-tolerant plants grow in the saltwater marshes, including aquatic grasses, cotton grasses, lungworts, and lyme grasses. Caribou and reindeer lichens grow in wetlands closer to forested areas.

Many waterfowl, such as the lesser snow goose, use the park in spring and fall as they migrate to their Arctic breeding grounds. Thousands of mallard ducks pass through in the fall, and the western and southwestern parts of the park form a migration path for shorebirds, such as the ruddy turnstone, black-bellied plover, and several species of sandpipers. Canada geese nest in the park.

Polar bears spend their summers in the park while breeding. Caribou and moose roam the area, moving north in the warmer weather. Beavers, muskrats, otters, foxes, and wolves are just a few of the many other mammals that make the park their year-round home.

The Cree Indians live along the coastal areas and use the park for hunting, fishing, and trapping. The Cree own two hunting and fishing camps where guests can fish and hunt waterfowl, grouse, and snipe. No other non-native hunting or fishing is permitted.

Since 1970 the area has been protected from development. Commercial or industrial use of natural resources is prohibited. Most of the park is designated as wilderness zones, nature reserves, or historical zones, where wildlife is protected.

Usumacinta Delta

The Usumacinta (oo-soo-mah-SEEN-tah) Delta is the most extensive wetland on the Gulf Coast of Mexico. It contains freshwater lagoons, swamps, marshes, and mangrove swamps. Its waters are rich in nutrients and support a major coastal fishery.

Usumacinta Delta

Location: Gulf Coast of Mexico

Area: 2,470,000 acres (998,000 hectares)

Classification: Swamp, marsh, and mangrove swamp

Many waterbirds breed and winter in the area. These include herons, egrets, storks, ibises, and spoonbills. Shorebirds that winter in the delta are ducks and coots.

A few manatees from the West Indies can be found here, as well as the endangered Morelet’s crocodile.

Threats to the delta have come from drainage for agriculture and oil spills from a nearby oil field. Also, mangrove trees are being cut for timber.

Flow Country

The marshy area of Caithness and Sutherland countries is known as Flow Country. The name “flow” comes from an old Norse word meaning “marshy ground.” Flow Country is one of the largest blanket bogs in the world, and it is still growing. Some of the peat found here is more than 8,000 years old.

Flow Country

Location: Northeast corner of Scotland

Area: 902,681 square acres (365,310 hectares)

Classification: Blanket bog

Typical plants that grow in Flow Country include sphagnum moss, heather, purple moorgrass, sedges, and rushes. The insect-eating plant, sundew, inhabits the bog.

Many bird species are supported by the bog. Sixty-six percent of the European communities’ greenshanks and the entire population of black-throated divers live there.

The peat that grows in a blanket bog is very valuable as fuel for home heating and industrial use. Peat mining is endangering this ancient ecosystem. In the 1980s, the Scottish government and several private companies began planting pine and fir trees. The trees support the forestry industry, but will eventually take over the wetland. Planting was halted by 1990 and the land was purchased by the Royal Society for the Protection of Birds (RSPB) in 1995 to preserve 14,800 acres (6,000 hectares) of forest.

For More Information

BOOKS

Batzer, Darold P., and Rebecca R. Sharitz. Ecology of Freshwater and Estuarine Wetlands. Berkeley: University of California Press, 2007.

Cox, Donald D., and Shirley A. Peron. A Naturalist’s Guide to Wetland Plants: An Ecology for Eastern North America. Syracuse, NY: Syracuse University Press, 2002.

Fowler, Theda Braddock. Wetlands: an Introduction to Ecology, the Law, and Permitting. Lanham, MD: Government Institutes, 2007.

Mitsch, William J., and James G. Gosselink. Wetlands. 4th ed. Hoboken, NJ: Wiley: 2007.

Moore, Peter D. Wetlands. New York: Chelsea House, 2006.

Scrace, Carolyn. Life in the Wetlands. New York: Children’s Press, 2005.

Shea, John F., et al. Wetlands, Buffer Zones and Riverfront Areas: Wildlife Habitat and Endangered Species. Boston: MCLE, 2004.

Swarts, Frederick A. The Pantanal: Understanding and Preserving the World’s Largest Wetland. St. Paul, MN: Paragon House Publishers, 2000.

PERIODICALS

Johnson, Dan. “Wetlands: Going, Goings … Gone?” The Futurist. 35. 5 September 2001: 6.

Levathes, Louise E. “Mysteries of the Bog.” National Geographic. Vol. 171, No. 3, March 1987, pp. 397–420.

Mohlenbrock, Robert H. “Wetted Bliss: in a Louisiana Refuge, Different Degrees of Moisture Create Distinctive Woods.” Natural History. 117. 2 March 2008: 62.

Yalden, Derek. “Managing Moorland.” Biological Sciences Review. 18. 2 November 2005: 14.

ORGANIZATIONS

Environmental Protection Agency, Office of Wetlands, Oceans and Watersheds, Wetlands Division (4502F), 401 M Street SW, Washington, DC 20460, Phone: 202-260-2090, Internet: http://www.epa.gov.

National Wetlands Conservation Project, The Nature Conservancy, 1800 N Kent Street, Suite 800, Arlington, VA 22209, Phone: 800-628-6860; Internet: http://www.tnc.org.

WEB SITES

“America’s Wetlands.” Environmental Protection Agency. http://www.epa.gov/OWOW/wetlands/vital/what.html (accessed July 13, 2007).

“On Peatlands and Peat.” International Peat Society. http://www.peatsociety.fi (accessed July 13, 2007).

“Status and Trends of Wetlands of the Counterminous United States from 1998 to 2004.” U.S. Fish & Wildlife Service. http://wetlandsfws.er.usgs.gov/status_trends/National_Reports/trends_2005_report.pdf (accessed July 13, 2007).

Thurston High School, Biomes: http://ths.sps.lane.edu/biomes/index1.html (accessed July 13, 2007).

University of California at Berkeley: http://www.ucmp.berkeley.edu/glossary/gloss5/biome/index.html (accessed July 13, 2007).