搜尋結果
其他人也問了
What is a wetlands area?
Is a wetland completely covered by water?
Why are wetland ecosystems important?
What are the different types of wetland?
2024年4月25日 · Definition of a Wetland. Wetlands are areas where water covers the soil, or is present either at or near the surface of the soil all year or for varying periods of time during the year, including during the growing season. Water saturation (hydrology) largely determines how the soil develops and the types of plant and animal ...
- Wetland Factsheet Series
Although wetlands are often wet, a wetland might not be ...
- Enhancing State and Tribal Programs
The goal of the Enhancing State and Tribal Programs ...
- States and Tribal Governments
Wetland Program Development Grants Students and ...
- The Science of Wetlands
Wetland Program Development Grants Students and ...
- Resources
Each phase of the study examines a cross-section of ...
- Types
Another common wetland classification system, used by ...
- Functions
The functions of a wetland and the values of these ...
- Contact Us
The contact us form for the Wetlands Protection and ...
- Wetland Factsheet Series
2023年10月19日 · A wetland is an area of land that is either covered by water or saturated with water. The water is often groundwater, seeping up from an aquifer or spring. A wetland ’s water can also come from a nearby river or lake. Seawater can also create wetlands, especially in coastal areas that experience strong tides.
- Overview
- Origin of wetlands
wetland, complex ecosystem characterized by flooding or saturation of the soil, which creates low-oxygen environments that favour a specialized assemblage of plants, animals, and microbes, which exhibit adaptations designed to tolerate periods of sluggishly moving or standing water. Wetlands are usually classified according to soil and plant life as bogs, marshes, swamps, and other similar environments.
Wetlands and the subdiscipline of wetland ecology are a relatively new area of study in the field of ecology, primarily arising out of the laws and other regulations enacted during the 1970s. The term wetland, however, was first used formally in 1953, in a report by the U.S. Fish and Wildlife Service (USFWS) that provided a framework for a later publication concerning waterfowl habitat in the United States. Since then, wetlands have been variously defined by ecologists and government officials. No single, formal definition exists; however, the definition provided by the Ramsar Convention, an intergovernmental treaty signed in Ramsar, Iran, in 1971 to guide national and international wetland-conservation measures, is among the most widely referenced:
Wetlands are areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres.
This definition is also broad enough to encompass open water used by birds—the concept that originally inspired the protection of wetlands and associated aquatic sites.
Britannica Quiz
Ecosystems
Evidence of the first wetland plants extends back to the Ordovician Period (485.4 million to 443.8 million years ago), when the first terrestrial plants, which were dependent on wet substrates, began to colonize the land. Wetland plants and the animals that depended on them continued to evolve, and the first marshes and swamps appeared during the Devonian Period (419.2 million to 358.9 million years ago). Swamps later dominated vast regions, such as the land that would become southern North America, during the Carboniferous Period (358.9 million to 298.9 million years ago), and parts of the Mesozoic and Cenozoic eras (252.2 million years ago to the present) were also characterized by the presence of extensive wetland habitats.
Wetland communities depend on access to liquid water. Throughout geologic history, water availability has varied according to prevailing local and global climate patterns, latitude, elevation, season, and distance from both water bodies and groundwater. As a result of this variability, wetland communities in different parts of the world are the product of different conditions.
Students save 67%! Learn more about our special academic rate today.
Learn More
Glaciation during the Pleistocene Epoch (2.6 million to 11,700 years ago) prepared several types of landscapes for the development of present-day wetlands. In glaciated regions, the movement of ice sheets scoured the landscape, and the weight of the ice depressed Earth’s crust below. Both processes created low-relief areas, such as the flat, scoured landscape of Canada’s Hudson Bay lowlands. This region, which hosts extensive wetlands that are fed by groundwater and precipitation, continues to experience isostatic uplift (a rebound in the land that follows a glacier’s retreat) that brings more of Hudson Bay’s bottom to the surface. Some of this new land has become vegetated, and the wetlands have expanded. As the Pleistocene glaciers retreated across the Northern Hemisphere, melt carved wide, flat valleys that are occupied today by major rivers and their associated wetlands and floodplains (flat land area adjacent to a stream). Uneven scouring of the landscape in some regions resulted in low spots that filled with melted snow and rainwater during particularly wet years. This process created the prairie pothole region of the Midwest and south-central Canada.
In some of the coldest parts of the world, wetlands are sustained by an impermeable layer of ice that remains in the soil throughout the year. This perennially frozen ground, or permafrost, prevents both the percolation of surface water into the ground and plant contact with mineral groundwater. About 20–22 percent of Earth’s land surface is close enough to a polar region or high enough in altitude to experience permafrost. Much of northern North America and Eurasia, as well as the Mongolian and Tibetan Plateaus, are affected by permafrost, and these regions host vast expanses of bogs, fens, and peatlands. North America possesses some of the most extensive bog and fen regions on Earth. In western Siberia, larch-spruce-birch forests form part of an enormous inland delta, which is the largest contiguous area of peatlands in the world. Asian plateaus in general host some of the most unusual high-altitude wetland ecosystems.
A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently for years or decades or seasonally for a shorter periods. Flooding results in oxygen-free anoxic processes prevailing, especially in the soils.
2023年2月24日 · What are wetlands? These diverse ecosystems are found on every continent except for Antarctica. Generally, they’re divided into two categories: coastal or inland. Coastal wetlands are a mix of...
2017年8月24日 · A wetland is a place in which the land is covered by water—salt, fresh, or somewhere in between—either seasonally or permanently. It functions as its own distinct ecosystem. You can recognize wetlands from other types of land or bodies of water primarily by the vegetation that has adapted to wet soil. © Roger Leguen / WWF-Canon.
What are wetlands? Wetlands are transitional areas, sandwiched between permanently flooded deepwater environments and well-drained uplands, where the water table is usually at or near the surface or the land is covered by shallow water.
