Wetlands and related terms:
A wetland is a land area that is saturated with water, either permanently or seasonally, such that it takes on the characteristics of a distinct ecosystem. The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play a number of roles in the environment, principally water purification, flood control, carbon sink and shoreline stability. Wetlands are also considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life. Wetlands occur naturally on every continent except Antarctica, the largest including the Amazon River basin, the West Siberian Plain, and the Pantanal in South America. The water found in wetlands can be freshwater, brackish, or saltwater. The main wetland types include swamps, marshes, bogs, and fens; and sub-types include mangrove, carr, pocosin, and varzea.
The UN Millennium Ecosystem Assessment determined that environmental degradation is more prominent within wetland systems than any other ecosystem on Earth.
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The word "estuary" is derived from the Latin word aestuarium meaning tidal inlet of the sea, which in itself is derived from the term aestus, meaning tide. There have been many definitions proposed to describe an estuary. The most widely accepted definition is: "a semi-enclosed coastal body of water, which has a free connection with the open sea, and within sea water is measurably diluted with freshwater derived from land drainage". However, this definition excludes a number of coastal water bodies such as coastal lagoons and brackish seas. A more comprehensive definition of an estuary is "a semi-enclosed body of water connected to the sea as far as the tidal limit or the salt intrusion limit and receiving freshwater runoff; however the freshwater inflow may not be perennial, the connection to the sea may be closed for part of the year and tidal influence may be negligible". This broad definition also includes fjords, lagoons, river mouths, and tidal creeks. An estuary is a dynamic ecosystem with a connection with the open sea through which the sea water enters with the rhythm of the tides. The sea water entering the estuary is diluted by the fresh water flowing from rivers and streams. The pattern of dilution varies between different estuaries and depends on the volume of fresh water, the tidal range, and the extent of evaporation of the water in the estuary.
Phytoplankton are key primary producers in estuaries.
Of the thirty-two largest cities in the world, twenty-two are located on estuaries. For example, New York City is located at the mouth of the Hudson River estuary.
As ecosystems, estuaries are under threat from human activities such as pollution and overfishing. They are also threatened by sewage, coastal settlement, land clearance and much more. Estuaries are affected by events far upstream, and concentrate materials such as pollutants and sediments. Land run-off and industrial, agricultural, and domestic waste enter rivers and are discharged into estuaries. Contaminants can be introduced which do not disintegrate rapidly in the marine environment, such as plastics, pesticides, furans, dioxins, phenols and heavy metals.
Such toxins can accumulate in the tissues of many species of aquatic life in a process called bioaccumulation. They also accumulate in benthic environments, such as estuaries and bay muds: a geological record of human activities of the last century.
For example, Chinese and Russian industrial pollution, such as phenols and heavy metals, has devastated fish stocks...
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What are wetlands -- as defined by the US Environmental Protection Agency
Wetlands are part of the foundation of our nation's water resources and are vital to the health of waterways and communities that are downstream. Wetlands feed downstream waters, trap floodwaters, recharge groundwater supplies, remove pollution, and provide fish and wildlife habitat. Wetlands are also economic drivers because of their key role in fishing, hunting, agriculture and recreation.
Wetlands include swamps, marshes and bogs. Wetlands vary widely because of differences in soils, topography, climate, hydrology, water chemistry, vegetation, and other factors.
Wetlands are often found alongside waterways and in flood plains. However, some wetlands have no apparent connection to surface water like rivers, lakes or the ocean, but have critical groundwater connections.
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What is an estuary -- as defined by the US Environmental Protection Agency
An estuary is a partially enclosed body of water along the coast where freshwater from rivers and streams meets and mixes with salt water from the ocean. Estuaries and the lands surrounding them are places of transition from land to sea and freshwater to salt water. Although influenced by the tides, they are protected from the full force of ocean waves, winds, and storms by such land forms as barrier islands or peninsulas.
Estuarine environments are among the most productive on earth, creating more organic matter each year than comparably-sized areas of forest, grassland, or agricultural land.
The tidal, sheltered waters of estuaries also support unique communities of plants and animals especially adapted for life at the margin of the sea.
Many different habitat types are found in and around estuaries, including shallow open waters, freshwater and salt marshes, swamps, sandy beaches, mud and sand flats, rocky shores, oyster reefs, mangrove forests, river deltas, tidal pools, and seagrasses.
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- Marine and Coastal Zone wetlands
- Marine waters—permanent shallow waters less than six metres deep at low tide; includes sea bays, straits
- Subtidal aquatic beds; includes kelp beds, seagrasses, tropical marine meadows
- Coral reefs
- Rocky marine shores; includes rocky offshore islands, sea cliffs
- Sand, shingle or pebble beaches; includes sand bars, spits, sandy islets
- Intertidal mud, sand or salt flats
- Intertidal marshes; includes saltmarshes, salt meadows, saltings, raised salt marshes, tidal brackish and freshwater marshes
- Intertidal forested wetlands; includes mangrove swamps, nipa swamps, tidal freshwater swamp forests
- Brackish to saline lagoons and marshes with one or more relatively narrow connections with the sea
- Freshwater lagoons and marshes in the coastal zone
- Non-tidal freshwater forested wetlands
- Inland wetlands
- Permanent rivers and streams; includes waterfalls
- Seasonal and irregular rivers and streams
- Inland deltas (permanent)
- Riverine floodplains; includes river flats, flooded river basins, seasonally flooded grassland, savanna and palm savanna
- Permanent freshwater lakes (> 8 ha); includes large oxbow lakes
- Seasonal/intermittent freshwater lakes (> 8 ha), floodplain lakes
- Permanent saline/brackish lakes
- Seasonal/intermittent saline lakes
- Permanent freshwater ponds (< 8 ha), marshes and swamps on inorganic soils; with emergent vegetation waterlogged for at least most of the growing season
- Seasonal/intermittent freshwater ponds and marshes on inorganic soils; includes sloughs, potholes; seasonally flooded meadows, sedge marshes
- Permanent saline/brackish marshes
- Seasonal saline marshes
- Shrub swamps; shrub-dominated freshwater marsh, shrub carr, alder thicket on inorganic soils
- Freshwater swamp forest; seasonally flooded forest, wooded swamps; on inorganic soils
- Peatlands; forest, shrub or open bogs
- Alpine and tundra wetlands; includes alpine meadows, tundra pools, temporary waters from snow melt
- Freshwater springs, oases and rock pools
- Geothermal wetlands
- Inland, subterranean karst wetlands
- Human-made wetlands
- Water storage areas; reservoirs, barrages, hydro-electric dams, impoundments (generally > 8 ha)
- Ponds, including farm ponds, stock ponds, small tanks (generally < 8 ha)
- Aquaculture ponds; fish ponds, shrimp ponds
- Salt exploitation; salt pans, salines
- Excavations; gravel pits, borrow pits, mining pools
- Wastewater treatment; sewage farms, settling ponds, oxidation basins
- Irrigated land and irrigation channels; rice fields, canals, ditches
- Seasonally flooded arable land, farm land
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