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The beaver is a keystone species, increasing biodiversity in its territory through creation of ponds and wetlands. [1] [2] As wetlands are formed and riparian habitats enlarged, aquatic plants colonize newly available watery habitat. Insect, invertebrate, fish, mammal, and bird diversities are also expanded. [3]
Wetlands exist on every continent, except Antarctica. [19] The water in wetlands is either freshwater, brackish or saltwater. [18] The main types of wetland are defined based on the dominant plants and the source of the water. For example, marshes are wetlands dominated by emergent herbaceous vegetation such as reeds, cattails and sedges.
Plant community composition can change dramatically over a gradient of groundwater depth: plants that can only survive in wetland conditions can be replaced by plants that are tolerant of drier conditions as groundwater levels are reduced, causing habitat community shifts and in some cases complete loss of riparian species. [7]
Wetland vary widely in their salinity levels, climate zones, and surrounding geography and play a crucial role in maintaining biodiversity, ecosystem services, and support human communities. [1] Wetlands cover at least six percent of the Earth and have become a focal issue for conservation due to the ecosystem services they provide.
Additionally, these plants provide a large habitat for many wetland species, a large number of which are endangered or threatened. Lastly, riparian plants shade the water from sunlight, reducing the heat stress on the water and aquatic life, while also providing nutrients in the form of organic matter.
Nutrients are recycled through the life cycle of organisms as they die and decompose, releasing the nutrients into the neighboring environment. "The service of nutrient cycling eventually impacts all other ecosystem services as all living things require a constant supply of nutrients to survive". [22]
For example, wetlands soils with high levels of acetate or hydrogen and carbon dioxide are conducive to methane production. Additionally, the type of plant life and amount of plant decomposition affects the nutrients available to the bacteria as well as the acidity.
Of these global tidal wetland losses and gains, 39% of losses and 14% of gains were attributed to direct human activities. [ 263 ] Approximately 40% of the global mangrove has been lost since the 1950's [ 264 ] with more than 9,736 km 2 of the world's mangroves continuing to be degraded in the 20 years period between 1996 and 2016. [ 265 ]